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Dodge GJ, Anderson AJ, He Y, Liu W, Viner R, Imperiali B. Mapping the architecture of the initiating phosphoglycosyl transferase from S. enterica O-antigen biosynthesis in a liponanoparticle. eLife 2024; 12:RP91125. [PMID: 38358918 PMCID: PMC10942596 DOI: 10.7554/elife.91125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2024] Open
Abstract
Bacterial cell surface glycoconjugates are critical for cell survival and for interactions between bacteria and their hosts. Consequently, the pathways responsible for their biosynthesis have untapped potential as therapeutic targets. The localization of many glycoconjugate biosynthesis enzymes to the membrane represents a significant challenge for expressing, purifying, and characterizing these enzymes. Here, we leverage cutting-edge detergent-free methods to stabilize, purify, and structurally characterize WbaP, a phosphoglycosyl transferase (PGT) from the Salmonella enterica (LT2) O-antigen biosynthesis. From a functional perspective, these studies establish WbaP as a homodimer, reveal the structural elements responsible for dimerization, shed light on the regulatory role of a domain of unknown function embedded within WbaP, and identify conserved structural motifs between PGTs and functionally unrelated UDP-sugar dehydratases. From a technological perspective, the strategy developed here is generalizable and provides a toolkit for studying other classes of small membrane proteins embedded in liponanoparticles beyond PGTs.
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Affiliation(s)
- Greg J Dodge
- Department of Biology and Department of Chemistry, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Alyssa J Anderson
- Department of Biology and Department of Chemistry, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Yi He
- Thermo Fisher ScientificSan JoseUnited States
| | - Weijing Liu
- Thermo Fisher ScientificSan JoseUnited States
| | - Rosa Viner
- Thermo Fisher ScientificSan JoseUnited States
| | - Barbara Imperiali
- Department of Biology and Department of Chemistry, Massachusetts Institute of TechnologyCambridgeUnited States
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2
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Musanna, Faridoon Khan U, Habib G, Gul H, Hayat A, Ur Rehman M. Contribution of the gyrA and waaG mutants to fluoroquinolones resistance, biofilm development, and persister cells formation in Salmonella enterica serovar Typhi. Gene 2024; 894:147943. [PMID: 37956962 DOI: 10.1016/j.gene.2023.147943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 09/01/2023] [Accepted: 10/27/2023] [Indexed: 11/21/2023]
Abstract
Fluoroquinolone resistance in Salmonella has been reported worldwide and poses a serious public health threat in developing countries. Multiple factors contribute to fluoroquinolone resistance, including mutations in DNA gyrase and the acquisition of antimicrobial resistance genes. Salmonella enterica serovar Typhi (S. Typhi) causes typhoid fever in humans, which is highly prevalent in counties with poor sanitation and hygiene standards. Here, we reported S. Typhi clinical isolates that showed varying degrees of susceptibility to fluoroquinolones and were characterized by Analytical Profile Index 20E test kit and 16S rRNA sequencing. S. Typhi strain S27 was resistant to fluoroquinolones and had multiple mutations in the gyrA gene. The gyrA lies in the quinolone resistance determining region of S. Typhi and has mutations at codon 83 (Ser83Phe), codon 87 (Asp87Gly), codon 308 (Lys308Glu), and codon 328 (Val328Ile). S. Typhi strain S6 has no gyrA mutations and is sensitive to fluoroquinolones but forms a strong biofilm relative to S. Typhi S27. Transcriptional analysis of biofilm associated genes revealed that the waaG gene was significantly downregulated. The ΔwaaG mutant showed a significant decrease in persister cells and a strong biofilm formation relative to wild type and gyrA mutant. The gyrA tetra mutant persister assay revealed a significant increase in persister cells compared to wild type and ΔwaaG. Collectively, this is the first report of S. Typhi's two key genes and their roles in antibiotic tolerance, biofilm formation, and fluoroquinolone resistance that can help in understanding the mechanism of persister formation and eradication.
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Affiliation(s)
- Musanna
- Department of Microbiology, Abbottabad University of Science and Technology, Havelian, Abbottabad 22500, Pakistan
| | - Ummara Faridoon Khan
- Department of Microbiology, Abbottabad University of Science and Technology, Havelian, Abbottabad 22500, Pakistan
| | - Gul Habib
- Department of Microbiology, Abbottabad University of Science and Technology, Havelian, Abbottabad 22500, Pakistan.
| | - Haji Gul
- Faculty of Veterinary and Animal Sciences, Gomal University, Dera Ismail Khan 29220, Pakistan; College of Animal Science and Technology, Anhui Agricultural University, No. 130 Changjiang West Road, Hefei 230036, China
| | - Azam Hayat
- Department of Microbiology, Abbottabad University of Science and Technology, Havelian, Abbottabad 22500, Pakistan
| | - Mujaddad Ur Rehman
- Department of Microbiology, Abbottabad University of Science and Technology, Havelian, Abbottabad 22500, Pakistan
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3
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Romeyer Dherbey J, Bertels F. The untapped potential of phage model systems as therapeutic agents. Virus Evol 2024; 10:veae007. [PMID: 38361821 PMCID: PMC10868562 DOI: 10.1093/ve/veae007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 12/18/2023] [Accepted: 01/12/2024] [Indexed: 02/17/2024] Open
Abstract
With the emergence of widespread antibiotic resistance, phages are an appealing alternative to antibiotics in the fight against multidrug-resistant bacteria. Over the past few years, many phages have been isolated from various environments to treat bacterial pathogens. While isolating novel phages for treatment has had some success for compassionate use, developing novel phages into a general therapeutic will require considerable time and financial resource investments. These investments may be less significant for well-established phage model systems. The knowledge acquired from decades of research on their structure, life cycle, and evolution ensures safe application and efficient handling. However, one major downside of the established phage model systems is their inability to infect pathogenic bacteria. This problem is not insurmountable; phage host range can be extended through genetic engineering or evolution experiments. In the future, breeding model phages to infect pathogens could provide a new avenue to develop phage therapeutic agents.
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Affiliation(s)
- Jordan Romeyer Dherbey
- Microbial Population Biology, Max Planck Institute for Evolutionary Biology, August-Thienemann-Straße 2, Plön, Schleswig-Holstein 24306, Germany
| | - Frederic Bertels
- Microbial Population Biology, Max Planck Institute for Evolutionary Biology, August-Thienemann-Straße 2, Plön, Schleswig-Holstein 24306, Germany
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4
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Patrick J, Pettersson P, Mäler L. Lipid- and substrate-induced conformational and dynamic changes in a glycosyltransferase involved in E. coli LPS synthesis revealed by 19F and 31P NMR. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184209. [PMID: 37558175 DOI: 10.1016/j.bbamem.2023.184209] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 07/03/2023] [Accepted: 08/04/2023] [Indexed: 08/11/2023]
Abstract
WaaG is a glycosyltransferase (GT) involved in the synthesis of the bacterial cell wall, and in Escherichia coli it catalyzes the transfer of a glucose moiety from the donor substrate UDP-glucose onto the nascent lipopolysaccharide (LPS) molecule which when completed constitutes the major component of the bacterium's outermost defenses. Similar to other GTs of the GT-B fold, having two Rossman-like domains connected by a short linker, WaaG is believed to undergo complex inter-domain motions as part of its function to accommodate the nascent LPS and UDP-glucose in the catalytic site located in the cleft between the two domains. As the nascent LPS is bulky and membrane-bound, WaaG is a peripheral membrane protein, adding to the complexity of studying the enzyme in a biologically relevant environment. Using specific 5-fluoro-Trp labelling of native and inserted tryptophans and 19F NMR we herein studied the dynamic interactions of WaaG with lipids using bicelles, and with the donor substrate. Line-shape changes when bicelles are added to WaaG show that the dynamic behavior is altered when binding to the model membrane, while a chemical shift change indicates an altered environment around a tryptophan located in the C-terminal domain of WaaG upon interaction with UDP-glucose or UDP. A lipid-bound paramagnetic probe was used to confirm that the membrane interaction is mediated by a loop region located in the N-terminal domain. Furthermore, the hydrolysis of the donor substrate by WaaG was quantified by 31P NMR.
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Affiliation(s)
- Joan Patrick
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Pontus Pettersson
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Lena Mäler
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden; Department of Chemistry, Umeå University, Umeå, Sweden.
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5
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Sabnis A, Edwards AM. Lipopolysaccharide as an antibiotic target. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2023; 1870:119507. [PMID: 37268022 DOI: 10.1016/j.bbamcr.2023.119507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 04/18/2023] [Accepted: 05/14/2023] [Indexed: 06/04/2023]
Abstract
Gram-negative bacteria, including Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii are amongst the highest priority drug-resistant pathogens, for which new antibiotics are urgently needed. Whilst antibiotic drug development is inherently challenging, this is particularly true for Gram-negative bacteria due to the presence of the outer membrane, a highly selective permeability barrier that prevents the ingress of several classes of antibiotic. This selectivity is largely due to an outer leaflet composed of the glycolipid lipopolysaccharide (LPS), which is essential for the viability of almost all Gram-negative bacteria. This essentiality, coupled with the conservation of the synthetic pathway across species and recent breakthroughs in our understanding of transport and membrane homeostasis has made LPS an attractive target for novel antibiotic drug development. Several different targets have been explored and small molecules developed that show promising activity in vitro. However, these endeavours have met limited success in clinical testing and the polymyxins, discovered more than 70 years ago, remain the only LPS-targeting drugs to enter the clinic thus far. In this review, we will discuss efforts to develop therapeutic inhibitors of LPS synthesis and transport and the reasons for limited success, and explore new developments in understanding polymyxin mode of action and the identification of new analogues with reduced toxicity and enhanced activity.
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Affiliation(s)
- Akshay Sabnis
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Rd, London SW7 2AZ, UK
| | - Andrew M Edwards
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Rd, London SW7 2AZ, UK.
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6
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Scaletti ER, Pettersson P, Patrick J, Shilling PJ, Westergren RG, Daley DO, Mäler L, Widmalm G, Stenmark P. Structural and functional insights into the Pseudomonas aeruginosa glycosyltransferase WaaG and the implications for lipopolysaccharide biosynthesis. J Biol Chem 2023; 299:105256. [PMID: 37716703 PMCID: PMC10579960 DOI: 10.1016/j.jbc.2023.105256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 08/31/2023] [Accepted: 09/10/2023] [Indexed: 09/18/2023] Open
Abstract
The glycosyltransferase WaaG in Pseudomonas aeruginosa (PaWaaG) is involved in the synthesis of the core region of lipopolysaccharides. It is a promising target for developing adjuvants that could help in the uptake of antibiotics. Herein, we have determined structures of PaWaaG in complex with the nucleotide-sugars UDP-glucose, UDP-galactose, and UDP-GalNAc. Structural comparison with the homolog from Escherichia coli (EcWaaG) revealed five key differences in the sugar-binding pocket. Solution-state NMR analysis showed that WT PaWaaG specifically hydrolyzes UDP-GalNAc and unlike EcWaaG, does not hydrolyze UDP-glucose. Furthermore, we found that a PaWaaG mutant (Y97F/T208R/N282A/T283A/T285I) designed to resemble the EcWaaG sugar binding site, only hydrolyzed UDP-glucose, underscoring the importance of the identified amino acids in substrate specificity. However, neither WT PaWaaG nor the PaWaaG mutant capable of hydrolyzing UDP-glucose was able to complement an E. coli ΔwaaG strain, indicating that more remains to be uncovered about the function of PaWaaG in vivo. This structural and biochemical information will guide future structure-based drug design efforts targeting PaWaaG.
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Affiliation(s)
- Emma R Scaletti
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Pontus Pettersson
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Joan Patrick
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Patrick J Shilling
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | | | - Daniel O Daley
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Lena Mäler
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Göran Widmalm
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, Sweden
| | - Pål Stenmark
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.
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7
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Dodge GJ, Anderson AJ, He Y, Liu W, Viner R, Imperiali B. Mapping the architecture of the initiating phosphoglycosyl transferase from S. enterica O-antigen biosynthesis in a liponanoparticle. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.16.545297. [PMID: 37398332 PMCID: PMC10312794 DOI: 10.1101/2023.06.16.545297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Bacterial cell surface glycoconjugates are critical for cell survival and for interactions between bacteria and their hosts. Consequently, the pathways responsible for their biosynthesis have untapped potential as therapeutic targets. The localization of many glycoconjugate biosynthesis enzymes to the membrane represents a significant challenge for expressing, purifying, and characterizing these enzymes. Here, we leverage cutting-edge methods to stabilize, purify, and structurally characterize WbaP, a phosphoglycosyl transferase (PGT) from Salmonella enterica (LT2) O-antigen biosynthesis without detergent solubilization from the lipid bilayer. From a functional perspective, these studies establish WbaP as a homodimer, reveal the structural elements responsible for oligomerization, shed light on the regulatory role of a domain of unknown function embedded within WbaP, and identify conserved structural motifs between PGTs and functionally unrelated UDP-sugar dehydratases. From a technological perspective, the strategy developed here is generalizable and provides a toolkit for studying small membrane proteins embedded in liponanoparticles beyond PGTs.
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Affiliation(s)
- Greg J. Dodge
- Department of Biology and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Alyssa J. Anderson
- Department of Biology and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Yi He
- Thermo Fisher Scientific, San Jose CA 95134, USA
| | - Weijing Liu
- Thermo Fisher Scientific, San Jose CA 95134, USA
| | - Rosa Viner
- Thermo Fisher Scientific, San Jose CA 95134, USA
| | - Barbara Imperiali
- Department of Biology and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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8
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Tang X, Yang T, Shen Y, Song X, Benghezal M, Marshall BJ, Tang H, Li H. Roles of Lipopolysaccharide Glycosyltransferases in Maintenance of Helicobacter pylori Morphology, Cell Wall Permeability, and Antimicrobial Susceptibilities. Int J Mol Sci 2023; 24:11381. [PMID: 37511140 PMCID: PMC10379358 DOI: 10.3390/ijms241411381] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 07/01/2023] [Accepted: 07/06/2023] [Indexed: 07/30/2023] Open
Abstract
Helicobacter pylori has a unique lipopolysaccharide structure that is essential in maintaining its cell envelope integrity and imbues the bacterium with natural resistance to cationic antimicrobial peptides (CAMPs). Our group has recently elucidated the complete set of LPS glycosyltransferase genes in H. pylori reference strain G27. Here, with a series of eight systematically constructed LPS glycosyltransferase gene mutants (G27ΔHP1578, G27ΔHP1283, G27ΔHP0159, G27ΔHP0479, G27ΔHP0102, G27ΔwecA, G27ΔHP1284 and G27ΔHP1191), we investigated the roles of H. pylori LPS glycosyltransferases in maintaining cell morphology, cell wall permeability, and antimicrobial susceptibilities. We demonstrated that deletion of these LPS glycosyltransferase genes did not interfere with bacterial cell wall permeability, but resulted in significant morphological changes (coccoid, coiled "c"-shape, and irregular shapes) after 48 h growth as compared to the rod-like cell shape of the wild-type strain. Moreover, as compared with the wild-type, none of the LPS mutants had altered susceptibility against clarithromycin, levofloxacin, amoxicillin, tetracycline, and metronidazole. However, the deletion of the conserved LPS glycosyltransferases, especially the O-antigen-initiating enzyme WecA, displayed a dramatic increase in susceptibility to the CAMP polymyxin B and rifampicin. Taken together, our findings suggest that the LPS glycosyltransferases play critical roles in the maintenance of the typical spiral morphology of H. pylori, as well as resistance to CAMPs and rifampicin. The LPS glycosyltransferases could be promising targets for developing novel anti-H. pylori drugs.
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Affiliation(s)
- Xiaoqiong Tang
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu 610041, China
- Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Tiankuo Yang
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu 610041, China
- Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Yalin Shen
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu 610041, China
- Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Xiaona Song
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu 610041, China
- Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Mohammed Benghezal
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu 610041, China
- Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Barry J Marshall
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu 610041, China
- Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, WA 6009, Australia
| | - Hong Tang
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu 610041, China
- Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Hong Li
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu 610041, China
- Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
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9
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Chatterjee R, Chowdhury AR, Nair AV, Hajra D, Kar A, Datey A, Shankar S, Mishra RK, Chandra N, Chakravortty D. Salmonella Typhimurium PgtE is an essential arsenal to defend against the host resident antimicrobial peptides. Microbiol Res 2023; 271:127351. [PMID: 36931126 DOI: 10.1016/j.micres.2023.127351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 02/19/2023] [Accepted: 03/05/2023] [Indexed: 03/12/2023]
Abstract
Salmonella enterica serovar Typhimurium is a common cause of gastroenteritis in humans and occasionally causes systemic infection. Salmonella's ability to survive and replicate within macrophages is an important characteristic during systemic infection. The outer membrane protease PgtE of S. enterica is a member of the Omptin family of outer membrane aspartate proteases which has well-characterized proteolytic activities in-vitro against a wide range of physiologically relevant substrates. However, no study has been done so far that draws a direct correlation between these in-vitro observations and the biology of the pathogen in-vivo. The main goals of this study were to characterize the pathogenesis-associated functions of pgtE and study its role in the intracellular survival and in-vivo virulence of Salmonella Typhimurium. Our study elucidated a possible role of Salmonella Typhimurium pgtE in combating host antimicrobial peptide- bactericidal/ permeability increasing protein (BPI) to survive in human macrophages. The pgtE-deficient strain of Salmonella showed attenuated proliferation and enhanced colocalization with BPI in U937 and Thp1 cells. In the presence of polymixin B, the attenuated in-vitro survival of STM ΔpgtE suggested a role of PgtE against the antimicrobial peptides. In addition, our study revealed that compared to the wild type Salmonella, the pgtE mutant is replication-deficient in C57BL/6 mice. Further, we showed that PgtE interacts directly with several antimicrobial peptides (AMPs) in the host gut. This gives the pathogen a survival advantage and helps to mount a successful infection in the host.
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Affiliation(s)
- Ritika Chatterjee
- Department of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, India
| | - Atish Roy Chowdhury
- Department of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, India
| | - Abhilash Vijay Nair
- Department of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, India
| | - Dipasree Hajra
- Department of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, India
| | - Arpita Kar
- Department of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, India
| | - Akshay Datey
- Centre for Biosystems Science and Engineering, Indian Institute of Science, Bangalore, India
| | - Santhosh Shankar
- Department of Biochemistry, Division of Biological Sciences, Indian Institute of Science, Bangalore, India
| | - Rishi Kumar Mishra
- Department of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, India
| | - Nagasuma Chandra
- Department of Biochemistry, Division of Biological Sciences, Indian Institute of Science, Bangalore, India
| | - Dipshikha Chakravortty
- Department of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, India; Adjunct Faculty, Indian Institute of Science Research and Education, Thiruvananthapuram, Kerala, India.
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10
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Cui H, Wang L, Zhang J. Synergistic influence on microbial communities ascribed to copper and tetracycline during aerobic composting: Insights into bacterial and fungal structures. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.1019494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
There are a considerable number of discussions aimed at analyzing microbial communities and their functions during the composting process. However, microbial succession under copper (Cu) and tetracycline (TCH)-stressed conditions has received less attention. Thus, this work analyzed the bacterial and fungal structures with high-throughput sequencing in Cu/TCH-amended composting (Cu: 0, 100, and 500 mg/kg; TCH: 0, 50, and 300 mg/kg), and the dominating controls on microbial diversity were identified using redundancy analysis (RDA) and structural equation models (SEMs). Low-concentration Cu increased the peak temperature (57°C) at the thermophilic phase. Composting phase-derived changes in bacterial and fungal communities were significant, while Cu and TCH showed a remarkable influence on fungi but not on bacteria. Cu and TCH inhibited Firmicutes' activity while promoting Actinobacteriota growth. Low-concentration Cu and TCH had a negative effect on Basidiomycota in the thermophilic phase and a positive influence on Chytridiomycota in the mature phase. TOC and TN were primary controls on the changes in microbial communities. NH4+-N and NO3--N were more beneficial to fungi with a contribution proportion of 42.13 and 16.85%, respectively. These findings could provide theoretical guidance for the directional research on microbial inoculants.
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11
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Proteomic Profiling of Outer Membrane Vesicles Released by Escherichia coli LPS Mutants Defective in Heptose Biosynthesis. J Pers Med 2022; 12:jpm12081301. [PMID: 36013250 PMCID: PMC9410366 DOI: 10.3390/jpm12081301] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 08/03/2022] [Accepted: 08/08/2022] [Indexed: 11/17/2022] Open
Abstract
Escherichia coli releases outer membrane vesicles (OMVs) into the extracellular environment. OMVs, which contain the outer membrane protein, lipopolysaccharides (LPS), and genetic material, play an important role in immune response modulation. An isobaric tag for relative and absolute quantitation (iTRAQ) analysis was used to investigate OMV constituent proteins and their functions in burn trauma. OMV sizes ranged from 50 to 200 nm. Proteomics and Gene Ontology analysis revealed that ΔrfaC and ΔrfaG were likely involved in the upregulation of the structural constituent of ribosomes for the outer membrane and of proteins involved in protein binding and OMV synthesis. ΔrfaL was likely implicated in the downregulation of the structural constituent of the ribosome, translation, and cytosolic large ribosomal subunit. Kyoto Encyclopedia of Genes and Genomes analysis indicated that ΔrfaC and ΔrfaG downregulated ACP, ACEF, and ADHE genes; ΔrfaL upregulated ACP, ACEF, and ADHE genes. Heat map analysis demonstrated upregulation of galF, clpX, accA, fabB, and grpE and downregulation of pspA, ydiY, rpsT, and rpmB. These results suggest that RfaC, RfaG, and RfaL proteins were involved in outer membrane and LPS synthesis. Therefore, direct contact between wounds and LPS may lead to apoptosis, reduction in local cell proliferation, and delayed wound healing.
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12
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Valvano MA. Remodelling of the Gram-negative bacterial Kdo 2-lipid A and its functional implications. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 35394417 DOI: 10.1099/mic.0.001159] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The lipopolysaccharide (LPS) is a characteristic molecule of the outer leaflet of the Gram-negative bacterial outer membrane, which consists of lipid A, core oligosaccharide, and O antigen. The lipid A is embedded in outer membrane and provides an efficient permeability barrier, which is particularly important to reduce the permeability of antibiotics, toxic cationic metals, and antimicrobial peptides. LPS, an important modulator of innate immune responses ranging from localized inflammation to disseminated sepsis, displays a high level of structural and functional heterogeneity, which arise due to regulated differences in the acylation of the lipid A and the incorporation of non-stoichiometric modifications in lipid A and the core oligosaccharide. This review focuses on the current mechanistic understanding of the synthesis and assembly of the lipid A molecule and its most salient non-stoichiometric modifications.
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Affiliation(s)
- Miguel A Valvano
- Wellcome-Wolfson Institute for Experimental Medicine, Queen's University Belfast, Belfast, BT9 7BL, UK
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13
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Mohiuddin SG, Massahi A, Orman MA. High-Throughput Screening of a Promoter Library Reveals New Persister Mechanisms in Escherichia Coli. Microbiol Spectr 2022; 10:e0225321. [PMID: 35196813 PMCID: PMC8865558 DOI: 10.1128/spectrum.02253-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Accepted: 01/31/2022] [Indexed: 11/23/2022] Open
Abstract
Persister cells are a small subpopulation of phenotypic variants that survive high concentrations of bactericidal antibiotics. Their survival mechanisms are not heritable and can be formed stochastically or triggered by environmental stresses such as antibiotic treatment. In this study, high-throughput screening of an Escherichia coli promoter library and subsequent validation experiments identified several genes whose expression was upregulated by antibiotic treatment. Among the identified genes, waaG, guaA, and guaB were found to be important in persister cell formation in E. coli as their deletion significantly enhanced the sensitivity of cells to various antibiotics. The GuaA and GuaB enzymes form the upstream reactions of ppGpp (a global persister molecule) biosynthesis, and the deletion of guaA and guaB drastically perturbs the ppGpp regulon in E. coli. WaaG, a lipopolysaccharide glucosyltransferase, plays an important role in shaping the outer membrane structure, and the deletion of waaG dissipates the proton gradient (ΔpH) component of cellular proton motive force (PMF), perturbs cellular ATP production, and reduces type I persister formation in stationary phase. Active respiration in the stationary phase, which drives the PMF, was previously shown to play a critical role in type I persister formation, and our results associated with the waaG deficient strain further corroborate these findings. IMPORTANCE Persistence is a nonheritable trait by which normal growing cells switch phenotypically to antibiotic tolerant persister cells. This transient state enables persister cells to recover and grow into an antibiotic-sensitive population. Persister cells have been observed in many pathogenic and nonpathogenic bacteria. Previous studies highlight the complexity and diversity of bacterial persister-cell mechanisms, many of which still remain to be elucidated. Here, using promoter and knockout cell libraries in Escherichia coli, we have identified genes that reveal novel persister mechanisms. As persistence is a critical survival strategy that evolved in many bacteria, our study will enhance the current molecular-level understanding of this conserved mechanism.
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Affiliation(s)
- Sayed Golam Mohiuddin
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, USA
| | - Aslan Massahi
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, USA
| | - Mehmet A. Orman
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, USA
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14
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Riu F, Ruda A, Engström O, Muheim C, Mobarak H, Ståhle J, Kosma P, Carta A, Daley DO, Widmalm G. A Lead-Based Fragment Library Screening of the Glycosyltransferase WaaG from Escherichia coli. Pharmaceuticals (Basel) 2022; 15:ph15020209. [PMID: 35215321 PMCID: PMC8877264 DOI: 10.3390/ph15020209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Revised: 02/05/2022] [Accepted: 02/06/2022] [Indexed: 11/16/2022] Open
Abstract
Glucosyl transferase I (WaaG) in E. coli catalyzes the transfer of an α-d-glucosyl group to the inner core of the lipopolysaccharide (LPS) and plays an important role in the biogenesis of the outer membrane. If its activity could be inhibited, the integrity of the outer membrane would be compromised and the bacterium would be susceptible to antibiotics that are normally prevented from entering the cell. Herein, three libraries of molecules (A, B and C) were docked in the binding pocket of WaaG, utilizing the docking binding affinity as a filter to select fragment-based compounds for further investigations. From the results of the docking procedure, a selection of compounds was investigated by molecular dynamics (MD) simulations to obtain binding free energy (BFE) and KD values for ligands as an evaluation for the binding to WaaG. Derivatives of 1,3-thiazoles (A7 and A4) from library A and 1,3,4-thiadiazole (B33) from library B displayed a promising profile of BFE, with KD < mM, viz., 0.11, 0.62 and 0.04 mM, respectively. Further root-mean-square-deviation (RMSD), electrostatic/van der Waals contribution to the binding and H-bond interactions displayed a favorable profile for ligands A4 and B33. Mannose and/or heptose-containing disaccharides C1–C4, representing sub-structures of the inner core of the LPS, were also investigated by MD simulations, and compound C42− showed a calculated KD = 0.4 µM. In the presence of UDP-Glc2−, the best-docked pose of disaccharide C42− is proximate to the glucose-binding site of WaaG. A study of the variation in angle and distance was performed on the different portions of WaaG (N-, the C- domains and the hinge region). The Spearman correlation coefficient between the two variables was close to unity, where both variables increase in the same way, suggesting a conformational rearrangement of the protein during the MD simulation, revealing molecular motions of the enzyme that may be part of the catalytic cycle. Selected compounds were also analyzed by Saturation Transfer Difference (STD) NMR experiments. STD effects were notable for the 1,3-thiazole derivatives A4, A8 and A15 with the apo form of the protein as well as in the presence of UDP for A4.
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Affiliation(s)
- Federico Riu
- Department of Medical, Surgical and Experimental Sciences, University of Sassari, Via Muroni, 23A, 07100 Sassari, Italy; (F.R.); (A.C.)
| | - Alessandro Ruda
- Arrhenius Laboratory, Department of Organic Chemistry, Stockholm University, S-106 91 Stockholm, Sweden; (A.R.); (O.E.); (H.M.); (J.S.)
| | - Olof Engström
- Arrhenius Laboratory, Department of Organic Chemistry, Stockholm University, S-106 91 Stockholm, Sweden; (A.R.); (O.E.); (H.M.); (J.S.)
| | - Claudio Muheim
- Arrhenius Laboratory, Department of Biochemistry and Biophysics, Stockholm University, S-106 91 Stockholm, Sweden; (C.M.); (D.O.D.)
| | - Hani Mobarak
- Arrhenius Laboratory, Department of Organic Chemistry, Stockholm University, S-106 91 Stockholm, Sweden; (A.R.); (O.E.); (H.M.); (J.S.)
| | - Jonas Ståhle
- Arrhenius Laboratory, Department of Organic Chemistry, Stockholm University, S-106 91 Stockholm, Sweden; (A.R.); (O.E.); (H.M.); (J.S.)
| | - Paul Kosma
- Department of Chemistry, University of Natural Resources and Life Sciences—Vienna, 1190 Vienna, Austria;
| | - Antonio Carta
- Department of Medical, Surgical and Experimental Sciences, University of Sassari, Via Muroni, 23A, 07100 Sassari, Italy; (F.R.); (A.C.)
| | - Daniel O. Daley
- Arrhenius Laboratory, Department of Biochemistry and Biophysics, Stockholm University, S-106 91 Stockholm, Sweden; (C.M.); (D.O.D.)
| | - Göran Widmalm
- Arrhenius Laboratory, Department of Organic Chemistry, Stockholm University, S-106 91 Stockholm, Sweden; (A.R.); (O.E.); (H.M.); (J.S.)
- Correspondence:
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15
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Martorana AM, Moura ECCM, Sperandeo P, Di Vincenzo F, Liang X, Toone E, Zhou P, Polissi A. Degradation of Components of the Lpt Transenvelope Machinery Reveals LPS-Dependent Lpt Complex Stability in Escherichia coli. Front Mol Biosci 2022; 8:758228. [PMID: 35004843 PMCID: PMC8727689 DOI: 10.3389/fmolb.2021.758228] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 11/23/2021] [Indexed: 11/13/2022] Open
Abstract
Lipopolysaccharide (LPS) is a peculiar component of the outer membrane (OM) of many Gram-negative bacteria that renders these bacteria highly impermeable to many toxic molecules, including antibiotics. LPS is assembled at the OM by a dedicated intermembrane transport system, the Lpt (LPS transport) machinery, composed of seven essential proteins located in the inner membrane (IM) (LptB2CFG), periplasm (LptA), and OM (LptDE). Defects in LPS transport compromise LPS insertion and assembly at the OM and result in an overall modification of the cell envelope and its permeability barrier properties. LptA is a key component of the Lpt machine. It connects the IM and OM sub-complexes by interacting with the IM protein LptC and the OM protein LptD, thus enabling the LPS transport across the periplasm. Defects in Lpt system assembly result in LptA degradation whose stability can be considered a marker of an improperly assembled Lpt system. Indeed, LptA recruitment by its IM and OM docking sites requires correct maturation of the LptB2CFG and LptDE sub-complexes, respectively. These quality control checkpoints are crucial to avoid LPS mistargeting. To further dissect the requirements for the complete Lpt transenvelope bridge assembly, we explored the importance of LPS presence by blocking its synthesis using an inhibitor compound. Here, we found that the interruption of LPS synthesis results in the degradation of both LptA and LptD, suggesting that, in the absence of the LPS substrate, the stability of the Lpt complex is compromised. Under these conditions, DegP, a major chaperone–protease in Escherichia coli, is responsible for LptD but not LptA degradation. Importantly, LptD and LptA stability is not affected by stressors disturbing the integrity of LPS or peptidoglycan layers, further supporting the notion that the LPS substrate is fundamental to keeping the Lpt transenvelope complex assembled and that LptA and LptD play a major role in the stability of the Lpt system.
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Affiliation(s)
- Alessandra M Martorana
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università Degli Studi di Milano, Milan, Italy
| | - Elisabete C C M Moura
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università Degli Studi di Milano, Milan, Italy
| | - Paola Sperandeo
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università Degli Studi di Milano, Milan, Italy
| | - Flavia Di Vincenzo
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università Degli Studi di Milano, Milan, Italy
| | - Xiaofei Liang
- Department of Chemistry, Duke University, Durham, NC, United States
| | - Eric Toone
- Department of Chemistry, Duke University, Durham, NC, United States
| | - Pei Zhou
- Department of Chemistry, Duke University, Durham, NC, United States.,Department of Biochemistry, Duke University School of Medicine, Durham, NC, United States
| | - Alessandra Polissi
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università Degli Studi di Milano, Milan, Italy
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16
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Olivar-Casique IB, Medina-Aparicio L, Mayo S, Gama-Martínez Y, Rebollar-Flores JE, Martínez-Batallar G, Encarnación S, Calva E, Hernández-Lucas I. The human bile salt sodium deoxycholate induces metabolic and cell envelope changes in Salmonella Typhi leading to bile resistance. J Med Microbiol 2022; 71. [PMID: 35006066 DOI: 10.1099/jmm.0.001461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Introduction. Salmonella enterica serovar Typhi (S. Typhi) is the etiological agent of typhoid fever. To establish an infection in the human host, this pathogen must survive the presence of bile salts in the gut and gallbladder.Hypothesis. S. Typhi uses multiple genetic elements to resist the presence of human bile.Aims. To determine the genetic elements that S. Typhi utilizes to tolerate the human bile salt sodium deoxycholate.Methodology. A collection of S. Typhi mutant strains was evaluated for their ability to growth in the presence of sodium deoxycholate and ox-bile. Additionally, transcriptomic and proteomic responses elicited by sodium deoxycholate on S. Typhi cultures were also analysed.Results. Multiple transcriptional factors and some of their dependent genes involved in central metabolism, as well as in cell envelope, are required for deoxycholate resistance.Conclusion. These findings suggest that metabolic adaptation to bile is focused on enhancing energy production to sustain synthesis of cell envelope components exposed to damage by bile salts.
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Affiliation(s)
- Isaac B Olivar-Casique
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Liliana Medina-Aparicio
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Selena Mayo
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Yitzel Gama-Martínez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Javier E Rebollar-Flores
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Gabriel Martínez-Batallar
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Sergio Encarnación
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Edmundo Calva
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Ismael Hernández-Lucas
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
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17
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Identification of Multiple Low-Level Resistance Determinants and Coselection of Motility Impairment upon Sub-MIC Ceftriaxone Exposure in Escherichia coli. mSphere 2021; 6:e0077821. [PMID: 34787446 PMCID: PMC8597738 DOI: 10.1128/msphere.00778-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Resistance to third-generation cephalosporins among Gram-negative bacteria is a rapidly growing public health threat. Among the most commonly used third-generation cephalosporins is ceftriaxone. Bacterial exposure to sublethal or sub-MIC antibiotic concentrations occurs widely, from environmental residues to intermittently at the site of infection. Quality of ceftriaxone is also a concern, especially in low- and middle-income countries, with medicines having inappropriate active pharmaceutical ingredient (API) content or concentration. While focus has been largely on extended-spectrum β-lactamases and high-level resistance, there are limited data on specific chromosomal mutations and other pathways that contribute to ceftriaxone resistance under these conditions. In this work, Escherichia coli cells were exposed to a broad range of sub-MICs of ceftriaxone and mutants were analyzed using whole-genome sequencing. Low-level ceftriaxone resistance emerged after as low as 10% MIC exposure, with the frequency of resistance development increasing with concentration. Genomic analyses of mutants revealed multiple genetic bases. Mutations were enriched in genes associated with porins (envZ, ompF, ompC, and ompR), efflux regulation (marR), and the outer membrane and metabolism (galU and pgm), but none were associated with the ampC β-lactamase. We also observed selection of mgrB mutations. Notably, pleiotropic effects on motility and cell surface were selected for in multiple independent genes, which may have important consequences. Swift low-level resistance development after exposure to low ceftriaxone concentrations may result in reservoirs of bacteria with relevant mutations for survival and increased resistance. Thus, initiatives for broader surveillance of low-level antibiotic resistance and genomic resistance determinants should be pursued when resources are available. IMPORTANCE Ceftriaxone is a widely consumed antibiotic used to treat bacterial infections. Bacteria, however, are increasingly becoming resistant to ceftriaxone. Most work has focused on known mechanisms associated with high-level ceftriaxone resistance. However, bacteria are extensively exposed to low antibiotic concentrations, and there are limited data on the evolution of ceftriaxone resistance under these conditions. In this work, we observed that bacteria quickly developed low-level resistance due to both novel and previously described mutations in multiple different genes upon exposure to low ceftriaxone concentrations. Additionally, exposure also led to changes in motility and the cell surface, which can impact other processes associated with resistance and infection. Notably, low-level-resistant bacteria would be missed in the clinic, which uses set breakpoints. While they may require increased resources, this work supports continued initiatives for broader surveillance of low-level antibiotic resistance or their resistance determinants, which can serve as predictors of higher risk for clinical resistance.
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18
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A Genome-Scale Antibiotic Screen in Serratia marcescens Identifies YdgH as a Conserved Modifier of Cephalosporin and Detergent Susceptibility. Antimicrob Agents Chemother 2021; 65:e0078621. [PMID: 34491801 DOI: 10.1128/aac.00786-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Serratia marcescens, a member of the order Enterobacterales, is adept at colonizing health care environments and is an important cause of invasive infections. Antibiotic resistance is a daunting problem in S. marcescens because, in addition to plasmid-mediated mechanisms, most isolates have considerable intrinsic resistance to multiple antibiotic classes. To discover endogenous modifiers of antibiotic susceptibility in S. marcescens, a high-density transposon insertion library was subjected to sub-MICs of two cephalosporins, cefoxitin, and cefepime, as well as the fluoroquinolone ciprofloxacin. Comparisons of transposon insertion abundance before and after antibiotic exposure identified hundreds of potential modifiers of susceptibility to these agents. Using single-gene deletions, we validated several candidate modifiers of cefoxitin susceptibility and chose ydgH, a gene of unknown function, for further characterization. In addition to cefoxitin, deletion of ydgH in S. marcescens resulted in decreased susceptibility to multiple third-generation cephalosporins and, in contrast, to increased susceptibility to both cationic and anionic detergents. YdgH is highly conserved throughout the Enterobacterales, and we observed similar phenotypes in Escherichia coli O157:H7 and Enterobacter cloacae mutants. YdgH is predicted to localize to the periplasm, and we speculate that it may be involved there in cell envelope homeostasis. Collectively, our findings provide insight into chromosomal mediators of antibiotic resistance in S. marcescens and will serve as a resource for further investigations of this important pathogen.
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19
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Lipidation of Class IV CdiA Effector Proteins Promotes Target Cell Recognition during Contact-Dependent Growth Inhibition. mBio 2021; 12:e0253021. [PMID: 34634941 PMCID: PMC8510554 DOI: 10.1128/mbio.02530-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Contact-dependent growth inhibition (CDI) systems enable the direct transfer of protein toxins between competing Gram-negative bacteria. CDI+ strains produce cell surface CdiA effector proteins that bind specific receptors on neighboring bacteria to initiate toxin delivery. Three classes of CdiA effectors that recognize different outer membrane protein receptors have been characterized in Escherichia coli to date. Here, we describe a fourth effector class that uses the lipopolysaccharide (LPS) core as a receptor to identify target bacteria. Selection for CDI-resistant target cells yielded waaF and waaP “deep-rough” mutants, which are unable to synthesize the full LPS core. The CDI resistance phenotypes of other waa mutants suggest that phosphorylated inner-core heptose residues form a critical CdiA recognition epitope. Class IV cdi loci also encode putative lysyl acyltransferases (CdiC) that are homologous to enzymes that lipidate repeats-in-toxin (RTX) cytolysins. We found that catalytically active CdiC is required for full target cell killing activity, and we provide evidence that the acyltransferase appends 3-hydroxydecanoate to a specific Lys residue within the CdiA receptor-binding domain. We propose that the lipid moiety inserts into the hydrophobic leaflet of lipid A to anchor CdiA interactions with the core oligosaccharide. Thus, LPS-binding CDI systems appear to have co-opted an RTX toxin-activating acyltransferase to increase the affinity of CdiA effectors for the target cell outer membrane.
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20
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Deciphering Microbial Metal Toxicity Responses via Random Bar Code Transposon Site Sequencing and Activity-Based Metabolomics. Appl Environ Microbiol 2021; 87:e0103721. [PMID: 34432491 DOI: 10.1128/aem.01037-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To uncover metal toxicity targets and defense mechanisms of the facultative anaerobe Pantoea sp. strain MT58 (MT58), we used a multiomic strategy combining two global techniques, random bar code transposon site sequencing (RB-TnSeq) and activity-based metabolomics. MT58 is a metal-tolerant Oak Ridge Reservation (ORR) environmental isolate that was enriched in the presence of metals at concentrations measured in contaminated groundwater at an ORR nuclear waste site. The effects of three chemically different metals found at elevated concentrations in the ORR contaminated environment were investigated: the cation Al3+, the oxyanion CrO42-, and the oxycation UO22+. Both global techniques were applied using all three metals under both aerobic and anaerobic conditions to elucidate metal interactions mediated through the activity of metabolites and key genes/proteins. These revealed that Al3+ binds intracellular arginine, CrO42- enters the cell through sulfate transporters and oxidizes intracellular reduced thiols, and membrane-bound lipopolysaccharides protect the cell from UO22+ toxicity. In addition, the Tol outer membrane system contributed to the protection of cellular integrity from the toxic effects of all three metals. Likewise, we found evidence of regulation of lipid content in membranes under metal stress. Individually, RB-TnSeq and metabolomics are powerful tools to explore the impact various stresses have on biological systems. Here, we show that together they can be used synergistically to identify the molecular actors and mechanisms of these pertubations to an organism, furthering our understanding of how living systems interact with their environment. IMPORTANCE Studying microbial interactions with their environment can lead to a deeper understanding of biological molecular mechanisms. In this study, two global techniques, RB-TnSeq and activity metabolomics, were successfully used to probe the interactions between a metal-resistant microorganism, Pantoea sp. strain MT58, and metals contaminating a site where the organism can be located. A number of novel metal-microbe interactions were uncovered, including Al3+ toxicity targeting arginine synthesis, which could lead to a deeper understanding of the impact Al3+ contamination has on microbial communities as well as its impact on higher-level organisms, including plants for whom Al3+ contamination is an issue. Using multiomic approaches like the one described here is a way to further our understanding of microbial interactions and their impacts on the environment overall.
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21
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Di Lorenzo F, Duda KA, Lanzetta R, Silipo A, De Castro C, Molinaro A. A Journey from Structure to Function of Bacterial Lipopolysaccharides. Chem Rev 2021; 122:15767-15821. [PMID: 34286971 DOI: 10.1021/acs.chemrev.0c01321] [Citation(s) in RCA: 72] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Lipopolysaccharide (LPS) is a crucial constituent of the outer membrane of most Gram-negative bacteria, playing a fundamental role in the protection of bacteria from environmental stress factors, in drug resistance, in pathogenesis, and in symbiosis. During the last decades, LPS has been thoroughly dissected, and massive information on this fascinating biomolecule is now available. In this Review, we will give the reader a third millennium update of the current knowledge of LPS with key information on the inherent peculiar carbohydrate chemistry due to often puzzling sugar residues that are uniquely found on it. Then, we will drive the reader through the complex and multifarious immunological outcomes that any given LPS can raise, which is strictly dependent on its chemical structure. Further, we will argue about issues that still remain unresolved and that would represent the immediate future of LPS research. It is critical to address these points to complete our notions on LPS chemistry, functions, and roles, in turn leading to innovative ways to manipulate the processes involving such a still controversial and intriguing biomolecule.
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Affiliation(s)
- Flaviana Di Lorenzo
- Department of Chemical Sciences, University of Naples Federico II, Via Cinthia 4, 80126 Naples, Italy.,Task Force on Microbiome Studies, University of Naples Federico II, Via Cinthia 4, 80126 Naples, Italy
| | - Katarzyna A Duda
- Research Center Borstel Leibniz Lung Center, Parkallee 4a, 23845 Borstel, Germany
| | - Rosa Lanzetta
- Department of Chemical Sciences, University of Naples Federico II, Via Cinthia 4, 80126 Naples, Italy
| | - Alba Silipo
- Department of Chemical Sciences, University of Naples Federico II, Via Cinthia 4, 80126 Naples, Italy.,Task Force on Microbiome Studies, University of Naples Federico II, Via Cinthia 4, 80126 Naples, Italy
| | - Cristina De Castro
- Task Force on Microbiome Studies, University of Naples Federico II, Via Cinthia 4, 80126 Naples, Italy.,Department of Agricultural Sciences, University of Naples Federico II, Via Università 96, 80055 Portici, Naples, Italy
| | - Antonio Molinaro
- Department of Chemical Sciences, University of Naples Federico II, Via Cinthia 4, 80126 Naples, Italy.,Task Force on Microbiome Studies, University of Naples Federico II, Via Cinthia 4, 80126 Naples, Italy.,Department of Chemistry, School of Science, Osaka University, 1-1 Osaka University Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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22
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Pagnout C, Razafitianamaharavo A, Sohm B, Caillet C, Beaussart A, Delatour E, Bihannic I, Offroy M, Duval JFL. Osmotic stress and vesiculation as key mechanisms controlling bacterial sensitivity and resistance to TiO 2 nanoparticles. Commun Biol 2021; 4:678. [PMID: 34083706 PMCID: PMC8175758 DOI: 10.1038/s42003-021-02213-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 05/11/2021] [Indexed: 02/04/2023] Open
Abstract
Toxicity mechanisms of metal oxide nanoparticles towards bacteria and underlying roles of membrane composition are still debated. Herein, the response of lipopolysaccharide-truncated Escherichia coli K12 mutants to TiO2 nanoparticles (TiO2NPs, exposure in dark) is addressed at the molecular, single cell, and population levels by transcriptomics, fluorescence assays, cell nanomechanics and electrohydrodynamics. We show that outer core-free lipopolysaccharides featuring intact inner core increase cell sensitivity to TiO2NPs. TiO2NPs operate as membrane strippers, which induce osmotic stress, inactivate cell osmoregulation and initiate lipid peroxidation, which ultimately leads to genesis of membrane vesicles. In itself, truncation of lipopolysaccharide inner core triggers membrane permeabilization/depolarization, lipid peroxidation and hypervesiculation. In turn, it favors the regulation of TiO2NP-mediated changes in cell Turgor stress and leads to efficient vesicle-facilitated release of damaged membrane components. Remarkably, vesicles further act as electrostatic baits for TiO2NPs, thereby mitigating TiO2NPs toxicity. Altogether, we highlight antagonistic lipopolysaccharide-dependent bacterial responses to nanoparticles and we show that the destabilized membrane can generate unexpected resistance phenotype.
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Affiliation(s)
| | | | | | | | | | - Eva Delatour
- Université de Lorraine, CNRS, LIEC, Metz, France
| | | | - Marc Offroy
- Université de Lorraine, CNRS, LIEC, Nancy, France
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23
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Salazar KC, Ma L, Green SI, Zulk JJ, Trautner BW, Ramig RF, Clark JR, Terwilliger AL, Maresso AW. Antiviral Resistance and Phage Counter Adaptation to Antibiotic-Resistant Extraintestinal Pathogenic Escherichia coli. mBio 2021; 12:e00211-21. [PMID: 33906920 PMCID: PMC8092219 DOI: 10.1128/mbio.00211-21] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 03/19/2021] [Indexed: 12/14/2022] Open
Abstract
Extraintestinal pathogenic Escherichia coli (ExPEC), often multidrug resistant (MDR), is a leading cause of urinary tract and systemic infections. The crisis of emergent MDR pathogens has led some to propose bacteriophages as a therapeutic. However, bacterial resistance to phage is a concerning issue that threatens to undermine phage therapy. Here, we demonstrate that E. coli sequence type 131, a circulating pandemic strain of ExPEC, rapidly develops resistance to a well-studied and therapeutically active phage (ϕHP3). Whole-genome sequencing of the resisters revealed truncations in genes involved in lipopolysaccharide (LPS) biosynthesis, the outer membrane transporter ompA, or both, implicating them as phage receptors. We found ExPEC resistance to phage is associated with a loss of fitness in host microenvironments and attenuation in a murine model of systemic infection. Furthermore, we constructed a novel phage-bacterium bioreactor to generate an evolved phage isolate with restored infectivity to all LPS-truncated ExPEC resisters. This study suggests that although the resistance of pandemic E. coli to phage is frequent, it is associated with attenuation of virulence and susceptibility to new phage variants that arise by directed evolution.IMPORTANCE In response to the rising crisis of antimicrobial resistance, bacteriophage (phage) therapy has gained traction. In the United States, there have been over 10 cases of largely successful compassionate-use phage therapy to date. The resilience of pathogens allowing their broad antibiotic resistance means we must also consider resistance to therapeutic phages. This work fills gaps in knowledge regarding development of phage resisters in a model of infection and finds critical fitness losses in those resisters. We also found that the phage was able to rapidly readapt to these resisters.
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Affiliation(s)
- Keiko C Salazar
- Department of Integrative Molecular and Biomedical Science, Baylor College of Medicine, Houston, Texas, USA
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA
| | - Li Ma
- School of Biological and Physical Sciences, Northwestern State University, Natchitoches, Louisiana, USA
| | - Sabrina I Green
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA
| | - Jacob J Zulk
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA
| | - Barbara W Trautner
- Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, USA
- Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Robert F Ramig
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA
| | - Justin R Clark
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA
| | - Austen L Terwilliger
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA
| | - Anthony W Maresso
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA
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24
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Hu J, Tang Y, Ai F, Lin M, Ruan J. Biofilm for leaching precious metals from waste printed circuit boards using biocyanidation technology. JOURNAL OF HAZARDOUS MATERIALS 2021; 403:123586. [PMID: 32795820 DOI: 10.1016/j.jhazmat.2020.123586] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 07/23/2020] [Accepted: 07/25/2020] [Indexed: 06/11/2023]
Abstract
Presently, biocyanidation technology is being usually adopted to recover precious metals from an increasing quantity of waste printed circuit boards. The main aim of this work was to investigate the biofilm formation of Pseudomonas and its ability to leach precious metals. Based on batch experiments, strain 113 showed the highest biofilm-forming activity in optimal culture conditions of pH 7.0, 25 °C, and 1/25 NB medium among the Pseudomonas strains isolated. Both low concentrations of Cu2+ (500 ppm) and Ag+ (2.5 ppm) promoted biofilm formation. Under the optimal culture conditions for biofilm formation, the concentration of CN- was up to 5.0 ppm. In the continuous silver leaching experiment, the Ag+ concentration reached 4.0 ppm and the leaching efficiency was 14.7 % at 7 d. The results of this study may contribute to the construction of a bioreactor used for continuous leaching of waste printed circuit boards in an attempt to recover precious metals. Our results may also aid in the industrialization of biocyanidation technology.
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Affiliation(s)
- Jian Hu
- School of Environmental Science and Engineering, Yangzhou University, 196 Huayang Xi Road, Yangzhou, People's Republic of China.
| | - Yun Tang
- School of Environmental Science and Engineering, Yangzhou University, 196 Huayang Xi Road, Yangzhou, People's Republic of China
| | - Fangqiu Ai
- School of Environmental Science and Engineering, Yangzhou University, 196 Huayang Xi Road, Yangzhou, People's Republic of China
| | - Mi Lin
- School of Environmental Science and Engineering, Sun Yat-Sen University, 135 Xingang Xi Road, Guangzhou, 510275, People's Republic of China
| | - Jujun Ruan
- School of Environmental Science and Engineering, Sun Yat-Sen University, 135 Xingang Xi Road, Guangzhou, 510275, People's Republic of China.
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25
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Lundstedt EA, Simpson BW, Ruiz N. Lipopolysaccharide transport involves long-range coupling between cytoplasmic and periplasmic domains of the LptB 2FGC extractor. J Bacteriol 2020; 203:JB.00618-20. [PMID: 33361195 PMCID: PMC8095461 DOI: 10.1128/jb.00618-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 12/18/2020] [Indexed: 01/04/2023] Open
Abstract
The cell surface of the Gram-negative cell envelope contains lipopolysaccharide (LPS) molecules, which form a permeability barrier against hydrophobic antibiotics. The LPS transport (Lpt) machine composed of LptB2FGCADE forms a proteinaceous trans-envelope bridge that allows for the rapid and specific transport of newly synthesized LPS from the inner membrane (IM) to the outer membrane (OM). This transport is powered from the IM by the ATP-binding cassette transporter LptB2FGC. The ATP-driven cycling between closed- and open-dimer states of the ATPase LptB2 is coupled to the extraction of LPS by the transmembrane domains LptFG. However, the mechanism by which LPS moves from a substrate-binding cavity formed by LptFG at the IM to the first component of the periplasmic bridge, the periplasmic β-jellyroll domain of LptF, is poorly understood. To better understand how LptB2FGC functions in Escherichia coli, we searched for suppressors of a defective LptB variant. We found that defects in LptB2 can be suppressed by both structural modifications to the core oligosaccharide of LPS and changes in various regions of LptFG, including a periplasmic loop in LptF that connects the substrate-binding cavity in LptFG to the periplasmic β-jellyroll domain of LptF. These novel suppressors suggest that interactions between the core oligosaccharide of LPS and periplasmic regions in the transporter influence the rate of LPS extraction by LptB2FGC. Together, our genetic data reveal a path for the bi-directional coupling between LptB2 and LptFG that extends from the cytoplasm to the entrance to the periplasmic bridge of the transporter.IMPORTANCEGram-negative bacteria are intrinsically resistant to many antibiotics due to the presence of lipopolysaccharide (LPS) at their cell surface. LPS is transported from its site of synthesis at the inner membrane to the outer membrane by the Lpt machine. Lpt proteins form a transporter that spans the entire envelope and is thought to function similarly to a PEZ candy dispenser. This trans-envelope machine is powered by the cytoplasmic LptB ATPase through a poorly understood mechanism. Using genetic analyses in Escherichia coli, we found that LPS transport involves long-ranging bi-directional coupling across cellular compartments between cytoplasmic LptB and periplasmic regions of the Lpt transporter. This knowledge could be exploited in developing antimicrobials that overcome the permeability barrier imposed by LPS.
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Affiliation(s)
- Emily A Lundstedt
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA
| | - Brent W Simpson
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA
| | - Natividad Ruiz
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA
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26
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Vezina B, Petit GA, Martin JL, Halili MA. Prediction of Burkholderia pseudomallei DsbA substrates identifies potential virulence factors and vaccine targets. PLoS One 2020; 15:e0241306. [PMID: 33216758 PMCID: PMC7678975 DOI: 10.1371/journal.pone.0241306] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 10/12/2020] [Indexed: 11/19/2022] Open
Abstract
Identification of bacterial virulence factors is critical for understanding disease pathogenesis, drug discovery and vaccine development. In this study we used two approaches to predict virulence factors of Burkholderia pseudomallei, the Gram-negative bacterium that causes melioidosis. B. pseudomallei is naturally antibiotic resistant and there are no clinically available melioidosis vaccines. To identify B. pseudomallei protein targets for drug discovery and vaccine development, we chose to search for substrates of the B. pseudomallei periplasmic disulfide bond forming protein A (DsbA). DsbA introduces disulfide bonds into extra-cytoplasmic proteins and is essential for virulence in many Gram-negative organism, including B. pseudomallei. The first approach to identify B. pseudomallei DsbA virulence factor substrates was a large-scale genomic analysis of 511 unique B. pseudomallei disease-associated strains. This yielded 4,496 core gene products, of which we hypothesise 263 are DsbA substrates. Manual curation and database screening of the 263 mature proteins yielded 81 associated with disease pathogenesis or virulence. These were screened for structural homologues to predict potential B-cell epitopes. In the second approach, we searched the B. pseudomallei genome for homologues of the more than 90 known DsbA substrates in other bacteria. Using this approach, we identified 15 putative B. pseudomallei DsbA virulence factor substrates, with two of these previously identified in the genomic approach, bringing the total number of putative DsbA virulence factor substrates to 94. The two putative B. pseudomallei virulence factors identified by both methods are homologues of PenI family β-lactamase and a molecular chaperone. These two proteins could serve as high priority targets for future B. pseudomallei virulence factor characterization.
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Affiliation(s)
- Ben Vezina
- Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia
| | - Guillaume A. Petit
- Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia
| | - Jennifer L. Martin
- Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia
- Vice-Chancellor’s Unit, University of Wollongong, Wollongong, New South Wales, Australia
| | - Maria A. Halili
- Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia
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27
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Zhong Z, Emond-Rheault JG, Bhandare S, Lévesque R, Goodridge L. Bacteriophage-Induced Lipopolysaccharide Mutations in Escherichia coli Lead to Hypersensitivity to Food Grade Surfactant Sodium Dodecyl Sulfate. Antibiotics (Basel) 2020; 9:E552. [PMID: 32872188 PMCID: PMC7558818 DOI: 10.3390/antibiotics9090552] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Revised: 08/24/2020] [Accepted: 08/26/2020] [Indexed: 01/11/2023] Open
Abstract
Bacteriophages (phages) are considered as one of the most promising antibiotic alternatives in combatting bacterial infectious diseases. However, one concern of employing phage application is the emergence of bacteriophage-insensitive mutants (BIMs). Here, we isolated six BIMs from E. coli B in the presence of phage T4 and characterized them using genomic and phenotypic methods. Of all six BIMs, a six-amino acid deletion in glucosyltransferase WaaG likely conferred phage resistance by deactivating the addition of T4 receptor glucose to the lipopolysaccharide (LPS). This finding was further supported by the impaired phage adsorption to BIMs and glycosyl composition analysis which quantitatively confirmed the absence of glucose in the LPS of BIMs. Since LPSs actively maintain outer membrane (OM) permeability, phage-induced truncations of LPSs destabilized the OM and sensitized BIMs to various substrates, especially to the food-grade surfactant sodium dodecyl sulfate (SDS). This hypersensitivity to SDS was exploited to design a T4-SDS combination which successfully prevented the generation of BIMs and eliminated the inoculated bacteria. Collectively, phage-driven modifications of LPSs immunized BIMs from T4 predation but increased their susceptibilities as a fitness cost. The findings of this study suggest a novel strategy to enhance the effectiveness of phage-based food safety interventions.
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Affiliation(s)
- Zeyan Zhong
- Food Science and Agricultural Chemistry, McGill University, Sainte-Anne-de-Bellevue, QC H3X 3V9 Canada;
| | - Jean-Guillaume Emond-Rheault
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Quebec City, QC G1V 0A6, Canada; (J.-G.E.-R.); (R.L.)
| | - Sudhakar Bhandare
- Operations Branch, Canadian Food Inspection Agency (CFIA), Charlottetown, PE C1E 1E3, Canada;
| | - Roger Lévesque
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Quebec City, QC G1V 0A6, Canada; (J.-G.E.-R.); (R.L.)
| | - Lawrence Goodridge
- Food Science Department, University of Guelph, Guelph, ON N1G 2W1, Canada
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28
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Maes M, Dyson ZA, Smith SE, Goulding DA, Ludden C, Baker S, Kellam P, Reece ST, Dougan G, Bartholdson Scott J. A novel therapeutic antibody screening method using bacterial high-content imaging reveals functional antibody binding phenotypes of Escherichia coli ST131. Sci Rep 2020; 10:12414. [PMID: 32709982 PMCID: PMC7382476 DOI: 10.1038/s41598-020-69300-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 06/26/2020] [Indexed: 01/28/2023] Open
Abstract
The increase of antimicrobial resistance (AMR), and lack of new classes of licensed antimicrobials, have made alternative treatment options for AMR pathogens increasingly attractive. Recent studies have demonstrated anti-bacterial efficacy of a humanised monoclonal antibody (mAb) targeting the O25b O-antigen of Escherichia coli ST131. To evaluate the phenotypic effects of antibody binding to diverse clinical E. coli ST131 O25b bacterial isolates in high-throughput, we designed a novel mAb screening method using high-content imaging (HCI) and image-based morphological profiling to screen a mAb targeting the O25b O-antigen. Screening the antibody against a panel of 86 clinical E. coli ST131 O25:H4 isolates revealed 4 binding phenotypes: no binding (18.60%), weak binding (4.65%), strong binding (69.77%) and strong agglutinating binding (6.98%). Impaired antibody binding could be explained by the presence of insertion sequences or mutations in O-antigen or lipopolysaccharide core biosynthesis genes, affecting the amount, structure or chain length of the O-antigen. The agglutinating binding phenotype was linked with lower O-antigen density, enhanced antibody-mediated phagocytosis and increased serum susceptibly. This study highlights the need to screen candidate mAbs against large panels of clinically relevant isolates, and that HCI can be used to evaluate mAb binding affinity and potential functional efficacy against AMR bacteria.
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Affiliation(s)
- Mailis Maes
- Department of Medicine, Cambridge Institute for Therapeutic Immunology & Infectious Disease, University of Cambridge, Cambridge, UK
| | - Zoe A Dyson
- Department of Medicine, Cambridge Institute for Therapeutic Immunology & Infectious Disease, University of Cambridge, Cambridge, UK
- Department of Infectious Diseases, Central Clinical School, Monash University, Melbourne, VIC, 3004, Australia
- London School of Hygiene and Tropical Medicine, London, UK
| | | | | | | | - Stephen Baker
- Department of Medicine, Cambridge Institute for Therapeutic Immunology & Infectious Disease, University of Cambridge, Cambridge, UK
| | - Paul Kellam
- Kymab Ltd, Babraham Research Campus, Cambridge, UK
- Department of Infectious Disease, Imperial College London, London, UK
| | | | - Gordon Dougan
- Department of Medicine, Cambridge Institute for Therapeutic Immunology & Infectious Disease, University of Cambridge, Cambridge, UK
| | - Josefin Bartholdson Scott
- Department of Medicine, Cambridge Institute for Therapeutic Immunology & Infectious Disease, University of Cambridge, Cambridge, UK.
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29
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Soh SM, Jang H, Mitchell RJ. Loss of the lipopolysaccharide (LPS) inner core increases the electrocompetence of Escherichia coli. Appl Microbiol Biotechnol 2020; 104:7427-7435. [PMID: 32676713 DOI: 10.1007/s00253-020-10779-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 06/28/2020] [Accepted: 07/05/2020] [Indexed: 12/19/2022]
Abstract
Mutations that shorten the lipopolysaccharide (LPS) in Escherichia coli were found to significantly increase the number of transformants after electroporation. The loss of the LPS outer core increased the number of transformants with plasmid pAmCyan (3.3 kb) from 5.0 × 105 colony-forming units (CFU)/μg in the wild-type E. coli BW25113 to 3.3 × 107 CFU/μg in a ΔwaaG background, a 66.2-fold increase in efficiency. Truncation of the inner core improved this even further, with the ΔwaaF mutant exhibiting the best transformation efficiencies obtained, i.e., a 454.7-fold increase in the number of colonies over the wild-type strain. Similar results were obtained when a larger plasmid (pDA1; 11.3 kb) was used, with the ΔwaaF mutant once more giving the best transformation rates, i.e., a 73.7-fold increase. Subsequent tests proved that the enhanced transformabilities of these mutants were not due to a better survival or their surface charge properties, nor from preferential binding of these strains to the plasmid. Using N-phenyl-1-naphthylamine (NPN), we confirmed that the outer membranes of these mutant strains were more permeable. We also found that they leaked more ATP (3.4- and 2.0-fold higher for the ΔwaaF and ΔwaaG mutants, respectively, than wild-type E. coli BW25113), suggesting that the inner membrane stability is also reduced, helping to explain how the DNA enters these cells more easily. KEY POINTS: • LPS inner core gene knockouts increase the electrocompetence of E. coli. • No significant difference in survival, surface charge, or DNA binding was evident. • The LPS inner core mutants, however, exhibited higher outer membrane permeability. • Their inner membranes were also leaky, based on supernatant ATP concentrations.
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Affiliation(s)
- Sandrine M Soh
- School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, South Korea
| | - Hyochan Jang
- School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, South Korea
| | - Robert J Mitchell
- School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, South Korea.
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30
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Structural analysis of the O-antigen polysaccharide from Escherichia coli O188. Carbohydr Res 2020; 498:108051. [PMID: 33075674 DOI: 10.1016/j.carres.2020.108051] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 05/26/2020] [Accepted: 05/26/2020] [Indexed: 02/07/2023]
Abstract
The structure of the O-antigen from Escherichia coli reference strain O188 (E. coli O188:H10) has been investigated. The lipopolysaccharide shows a typical nonrandom modal chain-length distribution and the sugar and absolute configuration analysis revealed d-Man, d-Glc, d-GlcN and d-GlcA as major components. The structure of the O-specific polysaccharide was determined using one- and two-dimensional 1H and 13C NMR spectroscopy experiments, where inter-residue correlations were identified by 1H,13C-heteronuclear multiple-bond correlation and 1H,1H-NOESY experiments, which revealed that it consists of pentasaccharide repeating units with the following structure: Biosynthetic aspects and NMR analysis are consistent with the presented structure as the biological repeating unit. The O-antigen of Shigella boydii type 16 differs only in that it carries O-acetyl groups to ~50% at O6 of the branch-point mannose residues. A molecular model of the E. coli O188 O-antigen containing 20 repeating units extends ~100 Å, which is similar to the height of the periplasmic portion of polysaccharide co-polymerase Wzz proteins that regulate the O-antigen chain length of lipopolysaccharides in the Wzx/Wzy biosynthetic pathway.
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31
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Colanic acid biosynthesis in Escherichia coli is dependent on lipopolysaccharide structure and glucose availability. Microbiol Res 2020; 239:126527. [PMID: 32590169 DOI: 10.1016/j.micres.2020.126527] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 06/06/2020] [Accepted: 06/06/2020] [Indexed: 01/31/2023]
Abstract
Lipopolysaccharide and colanic acid are important forms of exopolysaccharides located on the cell surface of Escherichia coli, but their interrelation with the cell stress response is not well understood. In this study, nine mutant strains with different structures of lipopolysaccharide were constructed from E. coli MG1655 by deletion of a single gene or multiple genes. All mutant strains did not produce colanic acid when grown in LB medium, but six of them could produce colanic acid when grown either in M9 medium in which glucose is the sole carbon source or in LB medium supplemented with glucose. The results indicate that colanic acid production in E. coli is dependent on both lipopolysaccharide structure and glucose availability. However, transcriptional analysis showed that 20 genes related to the colanic acid biosynthesis and the key gene rcsA in the Rcs system were all transcriptionally up-regulated in all of the nine mutant strains no matter they were grown in M9 or LB medium. This suggests that the availability of some nucleotide-sugar precursors shared by the biosynthesis of lipopolysaccharide and colanic acid might play a major role in colanic acid production in E. coli. Lipopolysaccharide pathway might have a huge priority to colanic acid pathway to use the common precursors; therefore, the colanic acid is not produced in MG1655 and the nine mutants when grown in LB medium. In the six mutant strains that can produce colanic acid in the glucose rich media, the common precursors might be abundant because they were not needed for synthesizing the mutant lipopolysaccharide.
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32
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Inactivation of the sfgtr4 Gene of Shigella flexneri Induces Biofilm Formation and Affects Bacterial Pathogenicity. Microorganisms 2020; 8:microorganisms8060841. [PMID: 32512756 PMCID: PMC7355660 DOI: 10.3390/microorganisms8060841] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 05/08/2020] [Accepted: 05/21/2020] [Indexed: 01/08/2023] Open
Abstract
Biofilm formation is a significant cause for the environmental persistence of foodborne pathogens. This phenomenon remains misunderstood in Shigellaflexneri whose pathogenicity is mainly associated with the virulence plasmid pWR100. Sequence analysis of the latter predicts a putative lipopolysaccharides (LPS) glycosyltransferase (Gtr) encoded by Sfgtr4, which is the second gene of the SfpgdA-orf186-virK-msbB2 locus. We demonstrated here that purified SfGtr4 exhibited a Gtr activity in vitro by transferring glucose to lipid A. To establish the role of SfGtr4 in virulence, we generated a Sfgtr4 mutant and assessed its phenotype in vitro. Sfgtr4 mutant significantly reduced HeLa cells invasion without impairing type III effectors secretion, increased susceptibility to lysozyme degradation, and enhanced bacterial killing by polymorphonuclear neutrophils (PMNs). SfGtr4 is related to proteins required in biofilm formation. We established conditions whereby wild-type Shigella formed biofilm and revealed that its appearance was accelerated by the Sfgtr4 mutant. Additional phenotypical analysis revealed that single SfpdgA and double SfpgdA-Sfgtr4 mutants behaved similarly to Sfgtr4 mutant. Furthermore, a molecular interaction between SfGtr4 and SfPgdA was identified. In summary, the dual contribution of SfGtr4 and SfPgdA to the pathogenicity and the regulation biofilm formation by S. flexneri was demonstrated here.
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33
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Chen Y, Boggess EE, Ocasio ER, Warner A, Kerns L, Drapal V, Gossling C, Ross W, Gourse RL, Shao Z, Dickerson J, Mansell TJ, Jarboe LR. Reverse engineering of fatty acid-tolerant Escherichia coli identifies design strategies for robust microbial cell factories. Metab Eng 2020; 61:120-130. [PMID: 32474056 DOI: 10.1016/j.ymben.2020.05.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2019] [Revised: 02/05/2020] [Accepted: 05/02/2020] [Indexed: 10/24/2022]
Abstract
Adaptive laboratory evolution is often used to improve the performance of microbial cell factories. Reverse engineering of evolved strains enables learning and subsequent incorporation of novel design strategies via the design-build-test-learn cycle. Here, we reverse engineer a strain of Escherichia coli previously evolved for increased tolerance of octanoic acid (C8), an attractive biorenewable chemical, resulting in increased C8 production, increased butanol tolerance, and altered membrane properties. Here, evolution was determined to have occurred first through the restoration of WaaG activity, involved in the production of lipopolysaccharides, then an amino acid change in RpoC, a subunit of RNA polymerase, and finally mutation of the BasS-BasR two component system. All three mutations were required in order to reproduce the increased growth rate in the presence of 20 mM C8 and increased cell surface hydrophobicity; the WaaG and RpoC mutations both contributed to increased C8 titers, with the RpoC mutation appearing to be the major driver of this effect. Each of these mutations contributed to changes in the cell membrane. Increased membrane integrity and rigidity and decreased abundance of extracellular polymeric substances can be attributed to the restoration of WaaG. The increase in average lipid tail length can be attributed to the RpoCH419P mutation, which also confers tolerance to other industrially-relevant inhibitors, such as furfural, vanillin and n-butanol. The RpoCH419P mutation may impact binding or function of the stringent response alarmone ppGpp to RpoC site 1. Each of these mutations provides novel strategies for engineering microbial robustness, particularly at the level of the microbial cell membrane.
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Affiliation(s)
- Yingxi Chen
- Department of Chemical and Biological Engineering, Iowa State University, Ames, IA, 50011, USA
| | - Erin E Boggess
- Department of Electrical and Computer Engineering, Iowa State University, Ames, IA, 50011, USA; Bioinformatics & Computational Biology Graduate Program, Iowa State University, Ames, IA, 50011, USA
| | - Efrain Rodriguez Ocasio
- NSF Center for Biorenewable Chemicals (CBiRC) Research Experience for Undergraduates, Ames, IA, 50011, USA; Industrial Biotechnology Program, University of Puerto Rico Mayagüez, 00681, Puerto Rico
| | - Aric Warner
- Interdepartmental Microbiology Graduate Program, Iowa State University, Ames, IA, 50011, USA
| | - Lucas Kerns
- Department of Chemical and Biological Engineering, Iowa State University, Ames, IA, 50011, USA
| | - Victoria Drapal
- NSF Center for Biorenewable Chemicals (CBiRC) Research Experience for Undergraduates, Ames, IA, 50011, USA; Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68508, USA
| | - Chloe Gossling
- Department of Chemical and Biological Engineering, Iowa State University, Ames, IA, 50011, USA
| | - Wilma Ross
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Richard L Gourse
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Zengyi Shao
- Department of Chemical and Biological Engineering, Iowa State University, Ames, IA, 50011, USA; Interdepartmental Microbiology Graduate Program, Iowa State University, Ames, IA, 50011, USA
| | - Julie Dickerson
- Department of Electrical and Computer Engineering, Iowa State University, Ames, IA, 50011, USA; Bioinformatics & Computational Biology Graduate Program, Iowa State University, Ames, IA, 50011, USA
| | - Thomas J Mansell
- Department of Chemical and Biological Engineering, Iowa State University, Ames, IA, 50011, USA; Interdepartmental Microbiology Graduate Program, Iowa State University, Ames, IA, 50011, USA.
| | - Laura R Jarboe
- Department of Chemical and Biological Engineering, Iowa State University, Ames, IA, 50011, USA; Interdepartmental Microbiology Graduate Program, Iowa State University, Ames, IA, 50011, USA.
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Pleiotropy complicates a trade-off between phage resistance and antibiotic resistance. Proc Natl Acad Sci U S A 2020; 117:11207-11216. [PMID: 32424102 PMCID: PMC7260982 DOI: 10.1073/pnas.1919888117] [Citation(s) in RCA: 132] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Bacteriophages (“phages,” viruses that infect bacteria) are an important source of selection for bacterial populations. Phages use various structures to infect bacterial cells, and bacteria often evolve phage resistance by losing or modifying these structures. We examine a phage that uses two structures that also provide Escherichia coli cells with antibiotic resistance. We show that phage selection can result in bacteria evolving phage resistance by losing or modifying the structures. When phage resistance evolves, the bacteria sometimes also show increased antibiotic sensitivity. This result indicates an evolutionary trade-off between phage resistance and antibiotic resistance. However, we also discovered bacterial mutations that avoid the trade-off. We discuss the potential use of phage selection and evolutionary trade-offs in treating bacterial infections. Bacteria frequently encounter selection by both antibiotics and lytic bacteriophages. However, the evolutionary interactions between antibiotics and phages remain unclear, in particular, whether and when phages can drive evolutionary trade-offs with antibiotic resistance. Here, we describe Escherichia coli phage U136B, showing it relies on two host factors involved in different antibiotic resistance mechanisms: 1) the efflux pump protein TolC and 2) the structural barrier molecule lipopolysaccharide (LPS). Since TolC and LPS contribute to antibiotic resistance, phage U136B should select for their loss or modification, thereby driving a trade-off between phage resistance and either of the antibiotic resistance mechanisms. To test this hypothesis, we used fluctuation experiments and experimental evolution to obtain phage-resistant mutants. Using these mutants, we compared the accessibility of specific mutations (revealed in the fluctuation experiments) to their actual success during ecological competition and coevolution (revealed in the evolution experiments). Both tolC and LPS-related mutants arise readily during fluctuation assays, with tolC mutations becoming more common during the evolution experiments. In support of the trade-off hypothesis, phage resistance via tolC mutations occurs with a corresponding reduction in antibiotic resistance in many cases. However, contrary to the hypothesis, some phage resistance mutations pleiotropically confer increased antibiotic resistance. We discuss the molecular mechanisms underlying this surprising pleiotropic result, consideration for applied phage biology, and the importance of ecology in evolution of phage resistance. We envision that phages may be useful for the reversal of antibiotic resistance, but such applications will need to account for unexpected pleiotropy and evolutionary context.
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35
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Genome-wide screens reveal Escherichia coli genes required for growth of T1-like phage LL5 and V5-like phage LL12. Sci Rep 2020; 10:8058. [PMID: 32415154 PMCID: PMC7229145 DOI: 10.1038/s41598-020-64981-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 04/17/2020] [Indexed: 01/08/2023] Open
Abstract
The host factor requirements of phages and mechanisms of mutational phage insensitivity must be characterized for rational design of phage cocktails. To characterize host dependencies of two novel Escherichia coli phages, the T1-like siphophage LL5 and the V5-like myophage LL12, forward genetic screens were conducted against the Keio collection, a library of single non-essential gene deletions in E. coli str. BW25113. These screens and subsequent experiments identified genes required by phages LL5 and LL12. E. coli mutants deficient in heptose II and the phosphoryl substituent of heptose I of the inner core lipopolysaccharide (LPS) were unable to propagate phage LL5, as were mutants deficient in the outer membrane protein TolC. Mutants lacking glucose I of the LPS outer core failed to propagate LL12. Two additional genes encoding cytoplasmic chaperones, PpiB and SecB, were found to be required for efficient propagation of phage LL5, but not LL12. This screening approach may be useful for identifying host factors dependencies of phages, which would provide valuable information for their potential use as therapeutics and for phage engineering.
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Lengers I, Herrmann F, Le Borgne M, Jose J. Improved Surface Display of Human Hyal1 and Identification of Testosterone Propionate and Chicoric Acid as New Inhibitors. Pharmaceuticals (Basel) 2020; 13:E54. [PMID: 32224932 PMCID: PMC7243119 DOI: 10.3390/ph13040054] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 03/18/2020] [Accepted: 03/24/2020] [Indexed: 02/03/2023] Open
Abstract
Degradation of high molecular weight hyaluronic acid (HA) in humans is mainly catalyzed by hyaluronidase Hyal1. This enzyme is involved in many pathophysiological processes and therefore appears an interesting target for drug discovery. Until now, only a few inhibitors of human Hyal1 are known due to obstacles in obtaining active enzymes for inhibitor screening. The aim of the present work was to provide a convenient enzyme activity assay and show its feasibility by the identification of new inhibitors. By autodisplay, Escherichia coli F470 can present active Hyal1 on its surface. In this study, the inducible expression of Hyal1 on the cell surface of E. coli under the control of a rhamnose-dependent promoter (Prha) was performed and optimized. Enzyme activity per single cell was increased by a factor of 100 compared to the constitutive Hyal1 surface display, as described before. An activity of 6.8 × 10-4 mU per single cell was obtained under optimal reaction conditions. By this modified activity assay, two new inhibitors of human Hyal1 were identified. Chicoric acid, a natural compound belonging to the phenylpropanoids, showed an IC50 value of 171 µM. The steroid derivative testosterone propionate showed and IC50 value of 124 ± 1.1 µM. Both values were in the same order of magnitude as the IC50 value of glycyrrhizic acid (177 µM), one of the best known inhibitors of human Hyal1 known so far. In conclusion, we established a new enzyme activity assay for human Hyal1 and identified new inhibitors with this new assay method.
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Affiliation(s)
- Isabelle Lengers
- Institute of Pharmaceutical and Medicinal Chemistry, PharmaCampus, Westfälische Wilhelms-Universtität Münster, 48149 Münster, Germany;
| | - Fabian Herrmann
- Institute of Pharmaceutical Biology and Phytochemistry, PharmaCampus, Westfälische Wilhelms-Universtität Münster, 48149 Münster, Germany;
| | - Marc Le Borgne
- Université de Lyon, Université Claude Bernard Lyon 1, Faculté de Pharmacie—ISPB, EA 4446 Bioactive Molecules and Medicinal Chemistry, SFR Santé Lyon-Est CNRS UMS3453—INSERM US7, 8 Avenue Rockefeller, F-69373 Lyon CEDEX 8, France;
| | - Joachim Jose
- Institute of Pharmaceutical and Medicinal Chemistry, PharmaCampus, Westfälische Wilhelms-Universtität Münster, 48149 Münster, Germany;
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Guo J, Chia GW, Berezhnoy NV, Cazenave-Gassiot A, Kjelleberg S, Hinks J, Mu Y, Seviour T. Bacterial lipopolysaccharide core structures mediate effects of butanol ingress. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183150. [DOI: 10.1016/j.bbamem.2019.183150] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 11/07/2019] [Accepted: 12/06/2019] [Indexed: 12/13/2022]
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Offroy M, Razafitianamaharavo A, Beaussart A, Pagnout C, Duval JFL. Fast automated processing of AFM PeakForce curves to evaluate spatially resolved Young modulus and stiffness of turgescent cells. RSC Adv 2020; 10:19258-19275. [PMID: 35515432 PMCID: PMC9054095 DOI: 10.1039/d0ra00669f] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Accepted: 05/08/2020] [Indexed: 01/12/2023] Open
Abstract
Atomic Force Microscopy (AFM) is a powerful technique for the measurement of mechanical properties of individual cells in two (x × y) or three (x × y × time) dimensions. The instrumental progress makes it currently possible to generate a large amount of data in a relatively short time, which is particularly true for AFM operating in so-called PeakForce tapping mode (Bruker corporation). The latter corresponds to an AFM probe that periodically hits the sample surface while the pico-newton level interaction force is recorded from cantilever deflection. The method provides unprecedented high-resolution (a few tens of nm) imaging of the mechanical features of soft biological samples (e.g. bacteria, yeasts) and of hard abiotic surfaces (e.g. minerals). The rapid conversion of up to several tens of thousands spatially resolved force curves typically collected in AFM PeakForce tapping mode over a given cell surface area into comprehensive nanomechanical information requires the development of robust data analysis methodologies and dedicated numerical tools. In this work, we report an automated algorithm for (i) a rapid and unambiguous detection of the indentation regimes corresponding to non-linear and linear deformations of bacterial surfaces upon compression by the AFM probe, (ii) the subsequent evaluation of the Young modulus and cell surface stiffness, and (iii) the generation of spatial mappings of relevant nanomechanical properties at the single cell level. The procedure involves consistent evaluation of the contact point between the AFM probe and sample biosurface and that of the threshold indentation value marking the transition between non-linear and linear deformation regimes. For comparison purposes, the former regime is here analyzed on the basis of Hertz and Sneddon models corrected or not for effects of finite sample thickness. Analysis of AFM measurements performed on a selected Escherichia coli strain is detailed to demonstrate the feasibility, rapidity and robustness of the here-proposed PeakForce data treatment process. The flexibility of the algorithm allows consideration of force curve parameterizations other than that detailed here, which may be desired for investigation of e.g. eukaryotes nanomechanics. The performance of the adopted Hertz-based and Sneddon-based contact mechanics formalisms in recovering experimental data and in identifying nanomechanical heterogeneities at the bacterium scale is further thoroughly discussed. A numerical method is proposed for the modeling of AFM PeakForce curves and the automated extraction of relevant spatially-resolved nanomechanical properties of turgescent cells.![]()
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Affiliation(s)
- Marc Offroy
- Université de Lorraine
- CNRS
- LIEC
- F-54000 Nancy
- France
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39
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Simpson DH, Hapeshi A, Rogers NJ, Brabec V, Clarkson GJ, Fox DJ, Hrabina O, Kay GL, King AK, Malina J, Millard AD, Moat J, Roper DI, Song H, Waterfield NR, Scott P. Metallohelices that kill Gram-negative pathogens using intracellular antimicrobial peptide pathways. Chem Sci 2019; 10:9708-9720. [PMID: 32015803 PMCID: PMC6977464 DOI: 10.1039/c9sc03532j] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 09/04/2019] [Indexed: 12/24/2022] Open
Abstract
A range of new water-compatible optically pure metallohelices - made by self-assembly of simple non-peptidic organic components around Fe ions - exhibit similar architecture to some natural cationic antimicrobial peptides (CAMPs) and are found to have high, structure-dependent activity against bacteria, including clinically problematic Gram-negative pathogens. A key compound is shown to freely enter rapidly dividing E. coli cells without significant membrane disruption, and localise in distinct foci near the poles. Several related observations of CAMP-like mechanisms are made via biophysical measurements, whole genome sequencing of tolerance mutants and transcriptomic analysis. These include: high selectivity for binding of G-quadruplex DNA over double stranded DNA; inhibition of both DNA gyrase and topoisomerase I in vitro; curing of a plasmid that contributes to the very high virulence of the E. coli strain used; activation of various two-component sensor/regulator and acid response pathways; and subsequent attempts by the cell to lower the net negative charge of the surface. This impact of the compound on multiple structures and pathways corresponds with our inability to isolate fully resistant mutant strains, and supports the idea that CAMP-inspired chemical scaffolds are a realistic approach for antimicrobial drug discovery, without the practical barriers to development that are associated with natural CAMPS.
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Affiliation(s)
- Daniel H Simpson
- Department of Chemistry , University of Warwick , Gibbet Hill Road , Coventry , CV4 7AL , UK .
| | - Alexia Hapeshi
- Warwick Medical School , University of Warwick , Coventry , CV4 7AL , UK
| | - Nicola J Rogers
- Department of Chemistry , University of Warwick , Gibbet Hill Road , Coventry , CV4 7AL , UK .
| | - Viktor Brabec
- The Czech Academy of Sciences , Institute of Biophysics , Kralovopolska 135 , CZ-61265 Brno , Czech Republic
| | - Guy J Clarkson
- Department of Chemistry , University of Warwick , Gibbet Hill Road , Coventry , CV4 7AL , UK .
| | - David J Fox
- Department of Chemistry , University of Warwick , Gibbet Hill Road , Coventry , CV4 7AL , UK .
| | - Ondrej Hrabina
- The Czech Academy of Sciences , Institute of Biophysics , Kralovopolska 135 , CZ-61265 Brno , Czech Republic
- Department of Biophysics , Palacky University , Slechtitelu 27 , 783 71 Olomouc , Czech Republic
| | - Gemma L Kay
- Warwick Medical School , University of Warwick , Coventry , CV4 7AL , UK
| | - Andrew K King
- Department of Chemistry , University of Warwick , Gibbet Hill Road , Coventry , CV4 7AL , UK .
| | - Jaroslav Malina
- The Czech Academy of Sciences , Institute of Biophysics , Kralovopolska 135 , CZ-61265 Brno , Czech Republic
| | - Andrew D Millard
- Warwick Medical School , University of Warwick , Coventry , CV4 7AL , UK
| | - John Moat
- School of Life Sciences , University of Warwick , Gibbet Hill Campus , Coventry , CV4 7AL , UK
| | - David I Roper
- School of Life Sciences , University of Warwick , Gibbet Hill Campus , Coventry , CV4 7AL , UK
| | - Hualong Song
- Department of Chemistry , University of Warwick , Gibbet Hill Road , Coventry , CV4 7AL , UK .
| | | | - Peter Scott
- Department of Chemistry , University of Warwick , Gibbet Hill Road , Coventry , CV4 7AL , UK .
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Isolation, Characterisation and Complete Genome Sequence of a Tequatrovirus Phage, Escherichia phage KIT03, Which Simultaneously Infects Escherichia coli O157:H7 and Salmonella enterica. Curr Microbiol 2019; 76:1130-1137. [DOI: 10.1007/s00284-019-01738-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 07/03/2019] [Indexed: 12/24/2022]
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41
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Pagnout C, Sohm B, Razafitianamaharavo A, Caillet C, Offroy M, Leduc M, Gendre H, Jomini S, Beaussart A, Bauda P, Duval JFL. Pleiotropic effects of rfa-gene mutations on Escherichia coli envelope properties. Sci Rep 2019; 9:9696. [PMID: 31273247 PMCID: PMC6609704 DOI: 10.1038/s41598-019-46100-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 06/17/2019] [Indexed: 01/18/2023] Open
Abstract
Mutations in the rfa operon leading to severely truncated lipopolysaccharide (LPS) structures are associated with pleiotropic effects on bacterial cells, which in turn generates a complex phenotype termed deep-rough. Literature reports distinct behavior of these mutants in terms of susceptibility to bacteriophages and to several antibacterial substances. There is so far a critical lack of understanding of such peculiar structure-reactivity relationships mainly due to a paucity of thorough biophysical and biochemical characterizations of the surfaces of these mutants. In the current study, the biophysicochemical features of the envelopes of Escherichia coli deep-rough mutants are identified from the molecular to the single cell and population levels using a suite of complementary techniques, namely microelectrophoresis, Atomic Force Microscopy (AFM) and Isobaric Tag for Relative and Absolute Quantitation (iTRAQ) for quantitative proteomics. Electrokinetic, nanomechanical and proteomic analyses evidence enhanced mutant membrane destabilization/permeability, and differentiated abundances of outer membrane proteins involved in the susceptibility phenotypes of LPS-truncated mutants towards bacteriophages, antimicrobial peptides and hydrophobic antibiotics. In particular, inner-core LPS altered mutants exhibit the most pronounced heterogeneity in the spatial distribution of their Young modulus and stiffness, which is symptomatic of deep damages on cell envelope likely to mediate phage infection process and antibiotic action.
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Affiliation(s)
- Christophe Pagnout
- Université de Lorraine, LIEC, UMR7360, Campus Bridoux, Metz, F-57070, France.
| | - Bénédicte Sohm
- Université de Lorraine, LIEC, UMR7360, Campus Bridoux, Metz, F-57070, France
| | | | - Céline Caillet
- Université de Lorraine, LIEC, UMR7360, Vandoeuvre-lès-Nancy, F-54000, France
| | - Marc Offroy
- Université de Lorraine, LIEC, UMR7360, Vandoeuvre-lès-Nancy, F-54000, France
| | - Marjorie Leduc
- Plateforme protéomique 3P5, Inserm U1016-Institut Cochin, Université Paris Descartes, MICUSPC, Paris, France
| | - Héloïse Gendre
- Université de Lorraine, LIEC, UMR7360, Vandoeuvre-lès-Nancy, F-54000, France
| | | | - Audrey Beaussart
- Université de Lorraine, LIEC, UMR7360, Vandoeuvre-lès-Nancy, F-54000, France
| | - Pascale Bauda
- Université de Lorraine, LIEC, UMR7360, Campus Bridoux, Metz, F-57070, France
| | - Jérôme F L Duval
- Université de Lorraine, LIEC, UMR7360, Vandoeuvre-lès-Nancy, F-54000, France
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42
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Abstract
The cell envelope is the first line of defense between a bacterium and the world-at-large. Often, the initial steps that determine the outcome of chemical warfare, bacteriophage infections, and battles with other bacteria or the immune system greatly depend on the structure and composition of the bacterial cell surface. One of the most studied bacterial surface molecules is the glycolipid known as lipopolysaccharide (LPS), which is produced by most Gram-negative bacteria. Much of the initial attention LPS received in the early 1900s was owed to its ability to stimulate the immune system, for which the glycolipid was commonly known as endotoxin. It was later discovered that LPS also creates a permeability barrier at the cell surface and is a main contributor to the innate resistance that Gram-negative bacteria display against many antimicrobials. Not surprisingly, these important properties of LPS have driven a vast and still prolific body of literature for more than a hundred years. LPS research has also led to pioneering studies in bacterial envelope biogenesis and physiology, mostly using Escherichia coli and Salmonella as model systems. In this review, we will focus on the fundamental knowledge we have gained from studies of the complex structure of the LPS molecule and the biochemical pathways for its synthesis, as well as the transport of LPS across the bacterial envelope and its assembly at the cell surface.
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43
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Crittenden CM, Escobar EE, Williams PE, Sanders JD, Brodbelt JS. Characterization of Antigenic Oligosaccharides from Gram-Negative Bacteria via Activated Electron Photodetachment Mass Spectrometry. Anal Chem 2019; 91:4672-4679. [PMID: 30844257 DOI: 10.1021/acs.analchem.9b00048] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Lipooligosaccharides (LOS), composed of hydrophilic oligosaccharides and hydrophobic lipid A domains, are found on the outer membranes of Gram-negative bacteria. Here we report the characterization of deacylated LOS of LPS by activated-electron photodetachment mass spectrometry. Collision induced dissociation (CID) of these phosphorylated oligosaccharides produces simple MS/MS spectra with most fragment ions arising from cleavages near the reducing end of the molecule where the phosphate groups are located. In contrast, 193 nm ultraviolet photodissociation (UVPD) generates a wide array of product ions throughout the oligosaccharide including cross-ring fragments that illuminate the branching patterns. However, there are also product ions that are redundant or uninformative, resulting in more congested spectra that complicate interpretation. In this work, a hybrid UVPD-CID approach known as activated-electron photodetachment (a-EPD) affords less congested spectra than UVPD alone and richer fragmentation patterns than CID alone. a-EPD combines UVPD of negatively charged oligosaccharides to yield abundant charge-reduced radical ions which are subsequently interrogated by collisional activation. CID of the charge-reduced precursors results in extensive fragmentation throughout the backbone of the oligosaccharide. This hybridized a-EPD approach was employed to characterize the structure and branching pattern of deacylated LOS of E. coli.
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Affiliation(s)
| | - Edwin E Escobar
- Department of Chemistry , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Peggy E Williams
- Department of Chemistry , University of Texas at Austin , Austin , Texas 78712 , United States
| | - James D Sanders
- Department of Chemistry , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Jennifer S Brodbelt
- Department of Chemistry , University of Texas at Austin , Austin , Texas 78712 , United States
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44
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Current Progress in the Structural and Biochemical Characterization of Proteins Involved in the Assembly of Lipopolysaccharide. Int J Microbiol 2018; 2018:5319146. [PMID: 30595696 PMCID: PMC6286764 DOI: 10.1155/2018/5319146] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 10/29/2018] [Indexed: 12/25/2022] Open
Abstract
The lipid component of the outer leaflet of the outer membrane of Gram-negative bacteria is primarily composed of the glycolipid lipopolysaccharide (LPS), which serves to form a protective barrier against hydrophobic toxins and many antibiotics. LPS is comprised of three regions: the lipid A membrane anchor, the nonrepeating core oligosaccharide, and the repeating O-antigen polysaccharide. The lipid A portion is also referred to as endotoxin as its overstimulation of the toll-like receptor 4 during systemic infection precipitates potentially fatal septic shock. Because of the importance of LPS for the viability and virulence of human pathogens, understanding how LPS is synthesized and transported to the outer leaflet of the outer membrane is important for developing novel antibiotics to combat resistant Gram-negative strains. The following review describes the current state of our understanding of the proteins responsible for the synthesis and transport of LPS with an emphasis on the contribution of protein structures to our understanding of their functions. Because the lipid A portion of LPS is relatively well conserved, a detailed description of the biosynthetic enzymes in the Raetz pathway of lipid A synthesis is provided. Conversely, less well-conserved biosynthetic enzymes later in LPS synthesis are described primarily to demonstrate conserved principles of LPS synthesis. Finally, the conserved LPS transport systems are described in detail.
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45
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Littlejohn JR, da Silva RF, Neale WA, Smallcombe CC, Clark HW, Mackay RMA, Watson AS, Madsen J, Hood DW, Burns I, Greenhough TJ, Shrive AK. Structural definition of hSP-D recognition of Salmonella enterica LPS inner core oligosaccharides reveals alternative binding modes for the same LPS. PLoS One 2018; 13:e0199175. [PMID: 29912941 PMCID: PMC6005524 DOI: 10.1371/journal.pone.0199175] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 06/02/2018] [Indexed: 12/21/2022] Open
Abstract
The crystal structures of a biologically and therapeutically active recombinant homotrimeric fragment of native human SP-D (hSP-D) complexed with the inner core oligosaccharide of the Salmonella enterica sv Minnesota rough strains R5 and R7 (rough mutant chemotypes Rc and Rd1) have been determined. The structures reveal that hSP-D specifically and preferentially targets the LPS inner core via the innermost conserved Hep-Kdo pair with the flexibility for alternative recognition when this preferred epitope is not available for binding. Hep-Kdo binding is achieved through calcium dependent recognition of the heptose dihydroxyethyl side chain coupled with specific interactions between the Kdo and the binding site flanking residues Arg343 and Asp325 with evidence for an extended binding site for LPS inner cores containing multiple Kdo residues. In one subunit of the R5-bound structure this preferred mode of binding is precluded by the crystal lattice and oligosaccharide is bound through the terminal inner core glucose. The structures presented here thus provide unique multiple insights into the recognition and binding of bacterial LPS by hSP-D. Not only is it demonstrated that hSP-D targets the highly conserved LPS proximal inner core Hep-Kdo motif, but also that hSP-D can recognise either terminal or non-terminal sugars and has the flexibility and versatility to adopt alternative strategies for bacterial recognition, utilising alternative LPS epitopes when the preferred inner core Hep-Kdo disaccharide is not available for binding.
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Affiliation(s)
| | - Ruben F. da Silva
- School of Life Sciences, Keele University, Staffordshire, United Kingdom
| | - William A. Neale
- School of Life Sciences, Keele University, Staffordshire, United Kingdom
| | | | - Howard W. Clark
- University of Southampton, Department of Child Health, Division of Clinical and Experimental Sciences, Sir Henry Wellcome Laboratories, Southampton General Hospital, Southampton, United Kingdom
- Southampton NIHR Respiratory Biomedical Research Unit, Southampton General Hospital, Southampton, United Kingdom
- Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
| | - Rose-Marie A. Mackay
- University of Southampton, Department of Child Health, Division of Clinical and Experimental Sciences, Sir Henry Wellcome Laboratories, Southampton General Hospital, Southampton, United Kingdom
| | - Alastair S. Watson
- University of Southampton, Department of Child Health, Division of Clinical and Experimental Sciences, Sir Henry Wellcome Laboratories, Southampton General Hospital, Southampton, United Kingdom
| | - Jens Madsen
- University of Southampton, Department of Child Health, Division of Clinical and Experimental Sciences, Sir Henry Wellcome Laboratories, Southampton General Hospital, Southampton, United Kingdom
- Southampton NIHR Respiratory Biomedical Research Unit, Southampton General Hospital, Southampton, United Kingdom
- Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
| | - Derek W. Hood
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell Science and Innovation Campus, Oxfordshire, United Kingdom
| | - Ian Burns
- School of Life Sciences, Keele University, Staffordshire, United Kingdom
| | | | - Annette K. Shrive
- School of Life Sciences, Keele University, Staffordshire, United Kingdom
- * E-mail:
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46
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Agrawal A, Weisshaar JC. Effects of alterations of the E. coli lipopolysaccharide layer on membrane permeabilization events induced by Cecropin A. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1470-1479. [PMID: 29684333 DOI: 10.1016/j.bbamem.2018.04.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 04/12/2018] [Accepted: 04/18/2018] [Indexed: 11/24/2022]
Abstract
The outermost layer of Gram negative bacteria is composed of a lipopolysaccharide (LPS) network that forms a dense protective hydrophilic barrier against entry of hydrophobic drugs. At low μM concentrations, a large family of cationic polypeptides known as antimicrobial peptides (AMPs) are able to penetrate the LPS layer and permeabilize the outer membrane (OM) and the cytoplasmic membrane (CM), causing cell death. Cecropin A is a well-studied cationic AMP from moth. Here a battery of time-resolved, single-cell microscopy experiments explores how deletion of sugar layers and/or phosphoryl negative charges from the core oligosaccharide layer (core OS) of K12 E. coli alters the timing of OM and CM permeabilization induced by Cecropin A. Deletion of sugar layers, or phosphoryl charges, or both from the core OS shortens the time to the onset of OM permeabilization to periplasmic GFP and also the lag time between OM permeabilization and CM permeabilization. Meanwhile, the 12-h minimum inhibitory concentration (MIC) changes only twofold with core OS alterations. The results suggest a two-step model in which the core oligosaccharide layers act as a kinetic barrier to penetration of Cecropin A to the lipid A outer leaflet of the OM. Once a threshold concentration has built up at the lipid A leaflet, nucleation occurs and the OM is locally permeabilized to GFP and, by inference, to Cecropin A. Whenever Cecropin A permeabilizes the OM, CM permeabilization always follows, and cell growth subsequently halts and never recovers on the 45 min observation timescale.
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Affiliation(s)
- Anurag Agrawal
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - James C Weisshaar
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA.
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47
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Nakamya MF, Ayoola MB, Park S, Shack LA, Swiatlo E, Nanduri B. The Role of Cadaverine Synthesis on Pneumococcal Capsule and Protein Expression. Med Sci (Basel) 2018; 6:E8. [PMID: 29351189 PMCID: PMC5872165 DOI: 10.3390/medsci6010008] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2017] [Revised: 01/07/2018] [Accepted: 01/09/2018] [Indexed: 12/25/2022] Open
Abstract
Invasive infections caused by Streptococcus pneumoniae, a commensal in the nasopharynx, pose significant risk to human health. Limited serotype coverage by the available polysaccharide-based conjugate vaccines coupled with increasing incidence of antibiotic resistance complicates therapeutic strategies. Bacterial physiology and metabolism that allows pathogens to adapt to the host are a promising avenue for the discovery of novel therapeutics. Intracellular polyamine concentrations are tightly regulated by biosynthesis, transport and degradation. We previously reported that deletion of cadA, a gene that encodes for lysine decarboxylase, an enzyme that catalyzes cadaverine synthesis results in an attenuated phenotype. Here, we report the impact of cadA deletion on pneumococcal capsule and protein expression. Our data show that genes for polyamine biosynthesis and transport are downregulated in ∆cadA. Immunoblot assays show reduced capsule in ∆cadA. Reduced capsule synthesis could be due to reduced transcription and availability of precursors for synthesis. The capsule is the predominant virulence factor in pneumococci and is critical for evading opsonophagocytosis and its loss in ∆cadA could explain the reported attenuation in vivo. Results from this study show that capsule synthesis in pneumococci is regulated by polyamine metabolism, which can be targeted for developing novel therapies.
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Affiliation(s)
- Mary F Nakamya
- Department of Basic Sciences, College of Veterinary Medicine, P.O. Box 6100, Mississippi State, MS 39762, USA.
| | - Moses B Ayoola
- Department of Basic Sciences, College of Veterinary Medicine, P.O. Box 6100, Mississippi State, MS 39762, USA.
| | - Seongbin Park
- Department of Basic Sciences, College of Veterinary Medicine, P.O. Box 6100, Mississippi State, MS 39762, USA.
| | - Leslie A Shack
- Department of Basic Sciences, College of Veterinary Medicine, P.O. Box 6100, Mississippi State, MS 39762, USA.
| | - Edwin Swiatlo
- Section of Infectious Diseases, Southeast Louisiana Veterans Health Care System, New Orleans, LA 70112, USA.
| | - Bindu Nanduri
- Department of Basic Sciences, College of Veterinary Medicine, P.O. Box 6100, Mississippi State, MS 39762, USA.
- Institute for Genomics, Biocomputing & Biotechnology, Mississippi State University, Mississippi State, MS 39762, USA.
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48
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Muheim C, Götzke H, Eriksson AU, Lindberg S, Lauritsen I, Nørholm MHH, Daley DO. Increasing the permeability of Escherichia coli using MAC13243. Sci Rep 2017; 7:17629. [PMID: 29247166 PMCID: PMC5732295 DOI: 10.1038/s41598-017-17772-6] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 11/30/2017] [Indexed: 01/21/2023] Open
Abstract
The outer membrane of gram-negative bacteria is a permeability barrier that prevents the efficient uptake of molecules with large scaffolds. As a consequence, a number of antibiotic classes are ineffective against gram-negative strains. Herein we carried out a high throughput screen for small molecules that make the outer membrane of Escherichia coli more permeable. We identified MAC13243, an inhibitor of the periplasmic chaperone LolA that traffics lipoproteins from the inner to the outer membrane. We observed that cells were (1) more permeable to the fluorescent probe 1-N-phenylnapthylamine, and (2) more susceptible to large-scaffold antibiotics when sub-inhibitory concentrations of MAC13243 were used. To exclude the possibility that the permeability was caused by an off-target effect, we genetically reconstructed the MAC13243-phenotype by depleting LolA levels using the CRISPRi system.
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Affiliation(s)
- Claudio Muheim
- Department of Biochemistry and Biophysics Stockholm University, Stockholm, Sweden
| | - Hansjörg Götzke
- Department of Biochemistry and Biophysics Stockholm University, Stockholm, Sweden
| | - Anna U Eriksson
- Chemical Biology Consortium Sweden, Laboratories for Chemical Biology, Umeå University, Umeå, Sweden
| | - Stina Lindberg
- Chemical Biology Consortium Sweden, Laboratories for Chemical Biology, Umeå University, Umeå, Sweden
| | - Ida Lauritsen
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kgs., Lyngby, Denmark
| | - Morten H H Nørholm
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kgs., Lyngby, Denmark
| | - Daniel O Daley
- Department of Biochemistry and Biophysics Stockholm University, Stockholm, Sweden.
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Liebau J, Fu B, Brown C, Mäler L. New insights into the membrane association mechanism of the glycosyltransferase WaaG from Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:683-690. [PMID: 29225173 DOI: 10.1016/j.bbamem.2017.12.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 11/30/2017] [Accepted: 12/05/2017] [Indexed: 12/11/2022]
Abstract
Monotopic glycosyltransferases (GTs) interact with membranes via electrostatic interactions. The N-terminal domain is permanently anchored to the membrane while the membrane interaction of the C-terminal domain is believed to be weaker so that it undergoes a functionally relevant conformational change upon donor or acceptor binding. Here, we studied the applicability of this model to the glycosyltransferase WaaG. WaaG is involved in the synthesis of lipopolysaccharides (LPS) in Gram-negative bacteria and was previously categorized as a monotopic GT. We analyzed the binding of WaaG to membranes by stopped-flow fluorescence and NMR diffusion experiments. We find that electrostatic interactions are required to bind WaaG to membranes while mere hydrophobic interactions are not sufficient. WaaG senses the membrane's surface charge density but there is no preferential binding to specific anionic lipids. However, the binding is weaker than expected for monotopic GTs but similar to peripheral GTs. Therefore, WaaG may be a peripheral GT and this could be of functional relevance in vivo since LPS synthesis occurs only when WaaG is membrane-bound. We could not observe a C-terminal domain movement under our experimental conditions.
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Affiliation(s)
- Jobst Liebau
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Biao Fu
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Christian Brown
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Lena Mäler
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden.
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pqiABC and yebST, Putative mce Operons of Escherichia coli, Encode Transport Pathways and Contribute to Membrane Integrity. J Bacteriol 2016; 199:JB.00606-16. [PMID: 27795327 DOI: 10.1128/jb.00606-16] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 10/04/2016] [Indexed: 01/01/2023] Open
Abstract
The membranes of single-cell organisms are crucial as the first line of defense. The outer membrane of Gram-negative bacteria is an asymmetric bilayer in which lipopolysaccharides (LPSs) and phospholipids are localized in the outer and inner leaflet, respectively. This asymmetry is important for membrane integrity. In Escherichia coli, the Mla transport pathway maintains this asymmetry by removing phospholipids from the outer leaflet. The MlaD component of this system is a mammalian cell entry (MCE) domain protein, and E. coli has two other MCE domain proteins of unknown function (PqiB and YebT). Here, we show that these two proteins are components of novel transport pathways that contribute to membrane integrity. The pqiAB operon is regulated by SoxS and RpoS. The yebST operon contains pqiAB homologues. Here, we found a third member of the pqi operon, ymbA (pqiC). A PqiB-PqiC complex bridges the inner and the outer membrane, and in other bacteria, pqiBC genes are located in operons together with transporter proteins. We show here that simultaneous deletion of pqiABC and yebST operons in an Δmla background rendered cells more sensitive to SDS-EDTA, and the SDS-EDTA sensitivity of mla mutants was rescued by additional copies of pqiABC We also found that the yebST operon was induced by a defect in LPS molecules. In conclusion, PqiABC and YebST are novel transport pathways related to the Mla transport pathway and important for membrane integrity. IMPORTANCE Membranes of bacteria are crucial for stress resistance. The composition of the E. coli outer membrane is asymmetric, with asymmetry maintained by the Mla ABC transport pathway. We propose that the stress-inducible pqiABC operon and homologous yebST operon, both of previously unknown function, encode transport pathway proteins related to the Mla transport pathway. Deletion of these operons rendered cells more sensitive to membrane stress, and additional copies of pqiABC suppressed the SDS-EDTA sensitivity of mla mutant strains. We found that yebS'-'lacZ fusion was activated in mutant strains with defective LPS molecules.
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