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Gao R, Zhang J, Geng H, Wang Y, Kang X, Geng S, Jiao X, Barrow P. The Loss of focA Gene Increases the Ability of Salmonella Enteritidis to Exit from Macrophages and Boosts Early Extraintestinal Spread for Systemic Infection in a Mouse Model. Microorganisms 2022; 10:microorganisms10081557. [PMID: 36013975 PMCID: PMC9414335 DOI: 10.3390/microorganisms10081557] [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: 06/23/2022] [Revised: 07/27/2022] [Accepted: 07/30/2022] [Indexed: 11/29/2022] Open
Abstract
Salmonella Enteritidis (SE) can spread from the intestines to cause systemic infection, mainly involving macrophages. Intramacrophage Salmonella exits and reinfects neighboring cells, leading to severe disease. Salmonella genes involved in exiting from macrophages are not well understood or fully identified. A focA::Tn5 mutant was identified by an in vitro assay, with increased ability to exit from macrophages. A defined SEΔfocA mutant and its complemented derivative strain, SEΔfocA::focA, were constructed to confirm this phenotype. Although the lethal ability of focA mutants was similar to that of the parental SE in mice, it was isolated earlier from the liver and spleen than the parental SE. focA mutants induced higher levels of proinflammatory IL-12 and TNF-α compared with the parental SE and SEΔfocA::focA. focA mutants showed higher cytotoxicity and lower formate concentrations than SE and SEΔfocA::focA, whereas there was no change in pyroptosis, apoptosis and flagella formation ability. These current data suggest that the focA gene plays an important role in regulating intramacrophage Salmonella exiting and extraintestinal spread in mice, although the specific mechanism requires further in-depth studies.
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Affiliation(s)
- Ran Gao
- Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou 225009, China; (R.G.); (J.Z.); (H.G.); (Y.W.); (X.K.); (X.J.)
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou 225009, China
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture of China, Yangzhou University, Yangzhou 225009, China
- Joint International Research Laboratory of Agriculture and Agri-Product Safety of the Ministry of Education, Yangzhou University, Yangzhou 225009, China
| | - Jian Zhang
- Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou 225009, China; (R.G.); (J.Z.); (H.G.); (Y.W.); (X.K.); (X.J.)
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou 225009, China
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture of China, Yangzhou University, Yangzhou 225009, China
- Joint International Research Laboratory of Agriculture and Agri-Product Safety of the Ministry of Education, Yangzhou University, Yangzhou 225009, China
| | - Haoyu Geng
- Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou 225009, China; (R.G.); (J.Z.); (H.G.); (Y.W.); (X.K.); (X.J.)
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou 225009, China
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture of China, Yangzhou University, Yangzhou 225009, China
- Joint International Research Laboratory of Agriculture and Agri-Product Safety of the Ministry of Education, Yangzhou University, Yangzhou 225009, China
| | - Yaonan Wang
- Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou 225009, China; (R.G.); (J.Z.); (H.G.); (Y.W.); (X.K.); (X.J.)
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou 225009, China
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture of China, Yangzhou University, Yangzhou 225009, China
- Joint International Research Laboratory of Agriculture and Agri-Product Safety of the Ministry of Education, Yangzhou University, Yangzhou 225009, China
| | - Xilong Kang
- Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou 225009, China; (R.G.); (J.Z.); (H.G.); (Y.W.); (X.K.); (X.J.)
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou 225009, China
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture of China, Yangzhou University, Yangzhou 225009, China
- Joint International Research Laboratory of Agriculture and Agri-Product Safety of the Ministry of Education, Yangzhou University, Yangzhou 225009, China
| | - Shizhong Geng
- Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou 225009, China; (R.G.); (J.Z.); (H.G.); (Y.W.); (X.K.); (X.J.)
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou 225009, China
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture of China, Yangzhou University, Yangzhou 225009, China
- Joint International Research Laboratory of Agriculture and Agri-Product Safety of the Ministry of Education, Yangzhou University, Yangzhou 225009, China
- Correspondence: ; Tel.: +86-(514)-87971136; Fax: +86-(514)-87991747
| | - Xin’an Jiao
- Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou 225009, China; (R.G.); (J.Z.); (H.G.); (Y.W.); (X.K.); (X.J.)
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou 225009, China
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture of China, Yangzhou University, Yangzhou 225009, China
- Joint International Research Laboratory of Agriculture and Agri-Product Safety of the Ministry of Education, Yangzhou University, Yangzhou 225009, China
| | - Paul Barrow
- School of Veterinary Medicine, University of Surrey, Daphne Jackson Road, Guildford GU2 7AL, UK;
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The interaction among gut microbes, the intestinal barrier and short chain fatty acids. ANIMAL NUTRITION (ZHONGGUO XU MU SHOU YI XUE HUI) 2022; 9:159-174. [PMID: 35573092 PMCID: PMC9079705 DOI: 10.1016/j.aninu.2021.09.012] [Citation(s) in RCA: 51] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 09/08/2021] [Accepted: 09/09/2021] [Indexed: 12/15/2022]
Abstract
The mammalian gut is inhabited by a massive and complicated microbial community, in which the host achieves a stable symbiotic environment through the interdependence, coordination, reciprocal constraints and participation in an immune response. The interaction between the host gut and the microbiota is essential for maintaining and achieving the homeostasis of the organism. Consequently, gut homeostasis is pivotal in safeguarding the growth and development and potential productive performance of the host. As metabolites of microorganisms, short chain fatty acids are not only the preferred energy metabolic feedstock for host intestinal epithelial cells, but also exert vital effects on antioxidants and the regulation of intestinal community homeostasis. Herein, we summarize the effects of intestinal microorganisms on the host gut and the mechanisms of action of short chain fatty acids on the four intestinal barriers of the organism, which will shed light on the manipulation of the intestinal community to achieve precise nutrition for specific individuals and provide a novel perspective for the prevention and treatment of diseases.
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3
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del Peso Santos T, Alvarez L, Sit B, Irazoki O, Blake J, Warner BR, Warr AR, Bala A, Benes V, Waldor MK, Fredrick K, Cava F. BipA exerts temperature-dependent translational control of biofilm-associated colony morphology in Vibrio cholerae. eLife 2021; 10:e60607. [PMID: 33588990 PMCID: PMC7886329 DOI: 10.7554/elife.60607] [Citation(s) in RCA: 9] [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: 07/01/2020] [Accepted: 02/03/2021] [Indexed: 12/18/2022] Open
Abstract
Adaptation to shifting temperatures is crucial for the survival of the bacterial pathogen Vibrio cholerae. Here, we show that colony rugosity, a biofilm-associated phenotype, is regulated by temperature in V. cholerae strains that naturally lack the master biofilm transcriptional regulator HapR. Using transposon-insertion mutagenesis, we found the V. cholerae ortholog of BipA, a conserved ribosome-associated GTPase, is critical for this temperature-dependent phenomenon. Proteomic analyses revealed that loss of BipA alters the synthesis of >300 proteins in V. cholerae at 22°C, increasing the production of biofilm-related proteins including the key transcriptional activators VpsR and VpsT, as well as proteins important for diverse cellular processes. At low temperatures, BipA protein levels increase and are required for optimal ribosome assembly in V. cholerae, suggesting that control of BipA abundance is a mechanism by which bacteria can remodel their proteomes. Our study reveals a remarkable new facet of V. cholerae's complex biofilm regulatory network.
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Affiliation(s)
- Teresa del Peso Santos
- The laboratory for Molecular Infection Medicine Sweden (MIMS), Department of Molecular Biology, Umeå UniversityUmeåSweden
| | - Laura Alvarez
- The laboratory for Molecular Infection Medicine Sweden (MIMS), Department of Molecular Biology, Umeå UniversityUmeåSweden
| | - Brandon Sit
- Howard Hughes Medical Institute, Brigham and Women's Hospital Division of Infectious Diseases and Harvard Medical School Department of Microbiology and ImmunobiologyBoston, MAUnited States
| | - Oihane Irazoki
- The laboratory for Molecular Infection Medicine Sweden (MIMS), Department of Molecular Biology, Umeå UniversityUmeåSweden
| | - Jonathon Blake
- Genomics Core Facility, European Molecular Biology Laboratory (EMBL)HeidelbergGermany
| | - Benjamin R Warner
- Department of Microbiology, The Ohio State UniversityColumbus, OHUnited States
- Center for RNA Biology, The Ohio State UniversityColumbus, OHUnited States
| | - Alyson R Warr
- Howard Hughes Medical Institute, Brigham and Women's Hospital Division of Infectious Diseases and Harvard Medical School Department of Microbiology and ImmunobiologyBoston, MAUnited States
| | - Anju Bala
- The laboratory for Molecular Infection Medicine Sweden (MIMS), Department of Molecular Biology, Umeå UniversityUmeåSweden
| | - Vladimir Benes
- Genomics Core Facility, European Molecular Biology Laboratory (EMBL)HeidelbergGermany
| | - Matthew K Waldor
- Howard Hughes Medical Institute, Brigham and Women's Hospital Division of Infectious Diseases and Harvard Medical School Department of Microbiology and ImmunobiologyBoston, MAUnited States
| | - Kurt Fredrick
- Department of Microbiology, The Ohio State UniversityColumbus, OHUnited States
- Center for RNA Biology, The Ohio State UniversityColumbus, OHUnited States
| | - Felipe Cava
- The laboratory for Molecular Infection Medicine Sweden (MIMS), Department of Molecular Biology, Umeå UniversityUmeåSweden
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The Yersinia pestis GTPase BipA Promotes Pathogenesis of Primary Pneumonic Plague. Infect Immun 2021; 89:IAI.00673-20. [PMID: 33257531 PMCID: PMC7822129 DOI: 10.1128/iai.00673-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 11/11/2020] [Indexed: 12/27/2022] Open
Abstract
Yersinia pestis is a highly virulent pathogen and the causative agent of bubonic, septicemic, and pneumonic plague. Primary pneumonic plague caused by inhalation of respiratory droplets contaminated with Y. pestis is nearly 100% lethal within 4 to 7 days without antibiotic intervention. Pneumonic plague progresses in two phases, beginning with extensive bacterial replication in the lung with minimal host responsiveness, followed by the abrupt onset of a lethal proinflammatory response. The precise mechanisms by which Y. pestis is able to colonize the lung and survive two very distinct disease phases remain largely unknown. To date, a few bacterial virulence factors, including the Ysc type 3 secretion system, are known to contribute to the pathogenesis of primary pneumonic plague. The bacterial GTPase BipA has been shown to regulate expression of virulence factors in a number of Gram-negative bacteria, including Pseudomonas aeruginosa, Escherichia coli, and Salmonella enterica serovar Typhi. However, the role of BipA in Y. pestis has yet to be investigated. Here, we show that BipA is a Y. pestis virulence factor that promotes defense against early neutrophil-mediated bacterial killing in the lung. This work identifies a novel Y. pestis virulence factor and highlights the importance of early bacterial/neutrophil interactions in the lung during primary pneumonic plague.
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5
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Choi E, Jeon H, Oh C, Hwang J. Elucidation of a Novel Role of YebC in Surface Polysaccharides Regulation of Escherichia coli bipA-Deletion. Front Microbiol 2020; 11:597515. [PMID: 33240252 PMCID: PMC7682190 DOI: 10.3389/fmicb.2020.597515] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Accepted: 10/23/2020] [Indexed: 12/19/2022] Open
Abstract
The BipA (BPI-inducible protein A) protein is ubiquitously conserved in various bacterial species and belongs to the translational GTPase family. Interestingly, the function of Escherichia coli BipA is not essential for cell growth under normal growth conditions. However, cultivation of bipA-deleted cells at 20°C leads to cold-sensitive growth defect and several phenotypic changes in ribosome assembly, capsule production, and motility, suggesting its global regulatory roles. Previously, our genomic library screening revealed that the overexpressed ribosomal protein (r-protein) L20 partially suppressed cold-sensitive growth defect by resolving the ribosomal abnormality in bipA-deleted cells at low temperature. Here, we explored another genomic library clone containing yebC, which encodes a predicted transcriptional factor that is not directly associated with ribosome biogenesis. Interestingly, overexpression of yebC in bipA-deleted cells diminished capsule synthesis and partially restored lipopolysaccharide (LPS) core maturation at a low temperature without resolving defects in ribosome assembly or motility, indicating that YebC may be specifically involved in the regulation of exopolysaccharide and LPS core synthesis. In this study, we collectively investigated the impacts of bipA-deletion on E. coli capsule, LPS, biofilm formation, and motility and revealed novel roles of YebC in extracellular polysaccharide production and LPS core synthesis at low temperature using this mutant strain. Furthermore, our findings suggest that ribosomal defects as well as increased capsule synthesis, and changes in LPS composition may contribute independently to the cold-sensitivity of bipA-deleted cells, implying multiple regulatory roles of BipA.
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Affiliation(s)
- Eunsil Choi
- Microbiological Resource Research Institute, Pusan National University, Busan, South Korea.,Department of Microbiology, Pusan National University, Busan, South Korea
| | - Hyerin Jeon
- Microbiological Resource Research Institute, Pusan National University, Busan, South Korea
| | - Changmin Oh
- Microbiological Resource Research Institute, Pusan National University, Busan, South Korea
| | - Jihwan Hwang
- Microbiological Resource Research Institute, Pusan National University, Busan, South Korea.,Department of Microbiology, Pusan National University, Busan, South Korea
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6
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Abdi M, Mirkalantari S, Amirmozafari N. Bacterial resistance to antimicrobial peptides. J Pept Sci 2019; 25:e3210. [DOI: 10.1002/psc.3210] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 07/04/2019] [Accepted: 07/21/2019] [Indexed: 12/12/2022]
Affiliation(s)
- Milad Abdi
- Student Research Committee, Faculty of MedicineIran University of Medical Sciences Tehran Iran
- Department of Microbiology, Faculty of MedicineIran University of Medical Sciences Tehran Iran
| | - Shiva Mirkalantari
- Department of Microbiology, Faculty of MedicineIran University of Medical Sciences Tehran Iran
| | - Nour Amirmozafari
- Department of Microbiology, Faculty of MedicineIran University of Medical Sciences Tehran Iran
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7
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Agrawal A, Rangarajan N, Weisshaar JC. Resistance of early stationary phase E. coli to membrane permeabilization by the antimicrobial peptide Cecropin A. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:182990. [PMID: 31129116 DOI: 10.1016/j.bbamem.2019.05.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 05/20/2019] [Accepted: 05/21/2019] [Indexed: 01/16/2023]
Abstract
Antimicrobial peptides (AMPs) cause bacterial membrane permeabilization and ultimately cell death at low μM concentrations. The membrane permeabilization action of a moth derived AMP Cecropin A on E. coli cells in exponential growth (mid-log phase) is well studied. At 1× MIC concentration, Cecropin A penetrates the lipopolysaccharide (LPS) barrier and causes outer membrane (OM) and cytoplasmic membrane (CM) permeabilization. For non-septating cells, permeabilization of both membranes begins at one pole. For septating cells, OM permeabilization begins at the septal region and CM permeabilization begins at one pole. However, in nature bacteria are frequently found in nutrient-starved conditions. Here we extend our single-cell microscopy assays to the attack of Cecropin A on E. coli cells in early stationary phase. Stationary phase E. coli is much more resistant to membrane permeabilization by Cecropin A than mid-log phase E. coli. A tenfold higher concentration of Cecropin A is required to observe CM permeabilization in the majority of stationary phase cells, and even then permeabilization proceeds more slowly. In addition, the spatial pattern of initial CM permeabilization changes from localized at one pole to global. Studies of lipid mutant strains suggest that a sufficient localized concentration of the anionic phospholipid phosphatidylglycerol (PG) guides the position of initial attack of the cationic AMP Cecropin A on the CM.
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Affiliation(s)
- Anurag Agrawal
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, 53706 Madison, WI, USA
| | - Nambirajan Rangarajan
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, 53706 Madison, WI, USA
| | - James C Weisshaar
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, 53706 Madison, WI, USA.
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8
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Nho SW, Abdelhamed H, Karsi A, Lawrence ML. Improving safety of a live attenuated Edwardsiella ictaluri vaccine against enteric septicemia of catfish and evaluation of efficacy. Vet Microbiol 2017; 210:83-90. [DOI: 10.1016/j.vetmic.2017.09.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 06/26/2017] [Accepted: 09/13/2017] [Indexed: 12/19/2022]
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9
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The Rcs-Regulated Colanic Acid Capsule Maintains Membrane Potential in Salmonella enterica serovar Typhimurium. mBio 2017; 8:mBio.00808-17. [PMID: 28588134 PMCID: PMC5461412 DOI: 10.1128/mbio.00808-17] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The Rcs phosphorelay and Psp (phage shock protein) systems are envelope stress responses that are highly conserved in gammaproteobacteria. The Rcs regulon was found to be strongly induced during metal deprivation of Salmonella enterica serovar Typhimurium lacking the Psp response. Nineteen genes activated by the RcsA-RcsB response regulator make up an operon responsible for the production of colanic acid capsular polysaccharide, which promotes biofilm development. Despite more than half a century of research, the physiological function of colanic acid has remained elusive. Here we show that Rcs-dependent colanic acid production maintains the transmembrane electrical potential and proton motive force in cooperation with the Psp response. Production of negatively charged exopolysaccharide covalently bound to the outer membrane may enhance the surface potential by increasing the local proton concentration. This provides a unifying mechanism to account for diverse Rcs/colanic acid-related phenotypes, including susceptibility to membrane-damaging agents and biofilm formation. Colanic acid is a negatively charged polysaccharide capsule produced by Escherichia coli, Salmonella, and other gammaproteobacteria. Research conducted over the 50 years since the discovery of colanic acid suggests that this exopolysaccharide plays an important role for bacteria living in biofilms. However, a precise physiological role for colanic acid has not been defined. In this study, we provide evidence that colanic acid maintains the transmembrane potential and proton motive force during envelope stress. This work provides a new and fundamental insight into bacterial physiology.
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10
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Bose T, Venkatesh KV, Mande SS. Computational Analysis of Host-Pathogen Protein Interactions between Humans and Different Strains of Enterohemorrhagic Escherichia coli. Front Cell Infect Microbiol 2017; 7:128. [PMID: 28469995 PMCID: PMC5395655 DOI: 10.3389/fcimb.2017.00128] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 03/28/2017] [Indexed: 01/18/2023] Open
Abstract
Serotype O157:H7, an enterohemorrhagic Escherichia coli (EHEC), is known to cause gastrointestinal and systemic illnesses ranging from diarrhea and hemorrhagic colitis to potentially fatal hemolytic uremic syndrome. Specific genetic factors like ompA, nsrR, and LEE genes are known to play roles in EHEC pathogenesis. However, these factors are not specific to EHEC and their presence in several non-pathogenic strains indicates that additional factors are involved in pathogenicity. We propose a comprehensive effort to screen for such potential genetic elements, through investigation of biomolecular interactions between E. coli and their host. In this work, an in silico investigation of the protein–protein interactions (PPIs) between human cells and four EHEC strains (viz., EDL933, Sakai, EC4115, and TW14359) was performed in order to understand the virulence and host-colonization strategies of these strains. Potential host–pathogen interactions (HPIs) between human cells and the “non-pathogenic” E. coli strain MG1655 were also probed to evaluate whether and how the variations in the genomes could translate into altered virulence and host-colonization capabilities of the studied bacterial strains. Results indicate that a small subset of HPIs are unique to the studied pathogens and can be implicated in virulence. This subset of interactions involved E. coli proteins like YhdW, ChuT, EivG, and HlyA. These proteins have previously been reported to be involved in bacterial virulence. In addition, clear differences in lineage and clade-specific HPI profiles could be identified. Furthermore, available gene expression profiles of the HPI-proteins were utilized to estimate the proportion of proteins which may be involved in interactions. We hypothesized that a cumulative score of the ratios of bound:unbound proteins (involved in HPIs) would indicate the extent of colonization. Thus, we designed the Host Colonization Index (HCI) measure to determine the host colonization potential of the E. coli strains. Pathogenic strains of E. coli were observed to have higher HCIs as compared to a non-pathogenic laboratory strain. However, no significant differences among the HCIs of the two pathogenic groups were observed. Overall, our findings are expected to provide additional insights into EHEC pathogenesis and are likely to aid in designing alternate preventive and therapeutic strategies.
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Affiliation(s)
- Tungadri Bose
- Bio-Sciences R&D Division, TCS Innovation Labs, Tata Consultancy Services LimitedPune, India.,Department of Chemical Engineering, Indian Institute of Technology BombayMumbai, India
| | - K V Venkatesh
- Department of Chemical Engineering, Indian Institute of Technology BombayMumbai, India
| | - Sharmila S Mande
- Bio-Sciences R&D Division, TCS Innovation Labs, Tata Consultancy Services LimitedPune, India
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Woods EC, McBride SM. Regulation of antimicrobial resistance by extracytoplasmic function (ECF) sigma factors. Microbes Infect 2017; 19:238-248. [PMID: 28153747 DOI: 10.1016/j.micinf.2017.01.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 01/20/2017] [Accepted: 01/21/2017] [Indexed: 11/27/2022]
Abstract
Extracytoplasmic function (ECF) sigma factors are a subfamily of σ70 sigma factors that activate genes involved in stress-response functions. In many bacteria, ECF sigma factors regulate resistance to antimicrobial compounds. This review will summarize the ECF sigma factors that regulate antimicrobial resistance in model organisms and clinically relevant pathogens.
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Affiliation(s)
- Emily C Woods
- Department of Microbiology and Immunology, Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, GA, USA
| | - Shonna M McBride
- Department of Microbiology and Immunology, Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, GA, USA.
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12
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Kassem II, Candelero-Rueda RA, Esseili KA, Rajashekara G. Formate simultaneously reduces oxidase activity and enhances respiration in Campylobacter jejuni. Sci Rep 2017; 7:40117. [PMID: 28091524 PMCID: PMC5238407 DOI: 10.1038/srep40117] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 12/02/2016] [Indexed: 02/06/2023] Open
Abstract
The foodborne microaerophilic pathogen, Campylobacter jejuni, possesses a periplasmic formate dehydrogenase and two terminal oxidases, which serve to metabolize formate and facilitate the use of oxygen as a terminal electron acceptor, respectively. Formate, a primary energy source for C. jejuni, inhibits oxidase activity in other bacteria. Here, we hypothesized that formate might affect both energy metabolism and microaerobic survival in C. jejuni. Subsequently, we showed that C. jejuni 81–176 (wildtype) exhibited enhanced chemoattraction to and respiration of formate in comparison to other organic acids. Formate also significantly increased C. jejuni’s growth, motility, and biofilm formation under microaerobic (5% O2) conditions. However, formate reduced oxidase activity under microaerobic conditions as well as aerotolerance and biofilm formation under ambient oxygen conditions. The expression of genes encoding the ribonucleotide reductase (RNR) and proteins that facilitate the use of alternative electron acceptors generally increased in the presence of formate. Taken together, formate might play a role in optimizing C. jejuni’s adaptation to the oxygen-limited gastrointestinal tract of the host. By affecting oxidase activity, formate possibly facilitates shuttling electrons to alternative acceptors, while likely conserving limited oxygen concentrations for other essential functions such as DNA synthesis via RNR which is required for C. jejuni’s growth.
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Affiliation(s)
- Issmat I Kassem
- Food Animal Health Research Program, Ohio Agricultural Research and Development Center, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, OH 44691, USA
| | - Rosario A Candelero-Rueda
- Food Animal Health Research Program, Ohio Agricultural Research and Development Center, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, OH 44691, USA
| | - Kawthar A Esseili
- Food Animal Health Research Program, Ohio Agricultural Research and Development Center, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, OH 44691, USA
| | - Gireesh Rajashekara
- Food Animal Health Research Program, Ohio Agricultural Research and Development Center, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, OH 44691, USA
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13
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de Almeida FA, Pimentel-Filho NDJ, Carrijo LC, Bento CBP, Baracat-Pereira MC, Pinto UM, de Oliveira LL, Vanetti MCD. Acyl homoserine lactone changes the abundance of proteins and the levels of organic acids associated with stationary phase in Salmonella Enteritidis. Microb Pathog 2017; 102:148-159. [DOI: 10.1016/j.micpath.2016.11.027] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 11/22/2016] [Accepted: 11/29/2016] [Indexed: 11/25/2022]
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14
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Sha J, Zhang C. Antibacterial activity identification of pCM19 and pCM12 derived from hGlyrichin. SPRINGERPLUS 2016; 5:1382. [PMID: 27610301 PMCID: PMC4993737 DOI: 10.1186/s40064-016-3025-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 08/09/2016] [Indexed: 11/10/2022]
Abstract
BACKGROUND hGlyrichin is a novel human antimicrobial peptide rich in glycine. The previous study of known human antimicrobial peptides indicated that in an eligible range, the greater corresponding antibacterial activity was consisted with the shorter peptide sequence. FINDINGS Two peptides named pCM19 and pCM12 were synthesized and the antibacterial activity assay results showed that these peptides exhibited strong antibacterial activity that was inversely proportional to the length of the peptide. Despite the effective inhibition of bacterial growth, the synthetic peptides showed no hemolytic effect on human red blood cells. CONCLUSIONS Taken together, these two peptides derived from hGlyrichin both have strong antibacterial activity and are not toxic to human somatic cells.
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Affiliation(s)
- Jibin Sha
- Beijing Institute of Radiation Medicine, 27 Taiping Road, Haidian District, Beijing, 10085 China ; School of Basic Sports Science, Shandong Sports University, Jinan, China
| | - Chenggang Zhang
- Beijing Institute of Radiation Medicine, 27 Taiping Road, Haidian District, Beijing, 10085 China
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15
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Tan L, Moriel DG, Totsika M, Beatson SA, Schembri MA. Differential Regulation of the Surface-Exposed and Secreted SslE Lipoprotein in Extraintestinal Pathogenic Escherichia coli. PLoS One 2016; 11:e0162391. [PMID: 27598999 PMCID: PMC5012682 DOI: 10.1371/journal.pone.0162391] [Citation(s) in RCA: 8] [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: 02/14/2016] [Accepted: 08/22/2016] [Indexed: 11/19/2022] Open
Abstract
Extra-intestinal pathogenic Escherichia coli (ExPEC) are responsible for diverse infections including meningitis, sepsis and urinary tract infections. The alarming rise in anti-microbial resistance amongst ExPEC complicates treatment and has highlighted the need for alternative preventive measures. SslE is a lipoprotein secreted by a dedicated type II secretion system in E. coli that was first identified as a potential vaccine candidate using reverse genetics. Although the function and protective efficacy of SslE has been studied, the molecular mechanisms that regulate SslE expression remain to be fully elucidated. Here, we show that while the expression of SslE can be detected in E. coli culture supernatants, different strains express and secrete different amounts of SslE when grown under the same conditions. While the histone-like transcriptional regulator H-NS strongly represses sslE at ambient temperatures, the variation in SslE expression at human physiological temperature suggested a more complex mode of regulation. Using a genetic screen to identify novel regulators of sslE in the high SslE-expressing strain UTI89, we defined a new role for the nucleoid-associated regulator Fis and the ribosome-binding GTPase TypA as positive regulators of sslE transcription. We also showed that Fis-mediated enhancement of sslE transcription is dependent on a putative Fis-binding sequence located upstream of the -35 sequence in the core promoter element, and provide evidence to suggest that Fis may work in complex with H-NS to control SslE expression. Overall, this study has defined a new mechanism for sslE regulation and increases our understanding of this broadly conserved E. coli vaccine antigen.
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Affiliation(s)
- Lendl Tan
- Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, QLD 4072, Brisbane, Australia
| | - Danilo G. Moriel
- Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, QLD 4072, Brisbane, Australia
| | - Makrina Totsika
- Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology, QLD 4059, Brisbane, Australia
| | - Scott A. Beatson
- Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, QLD 4072, Brisbane, Australia
| | - Mark A. Schembri
- Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, QLD 4072, Brisbane, Australia
- * E-mail:
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16
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Abstract
The emergence and spread of drug-resistant pathogens and our inability to develop new antimicrobials to overcome resistance has inspired scientists to consider new targets for drug development. Cellular bioenergetics is an area showing promise for the development of new antimicrobials, particularly in the discovery of new anti-tuberculosis drugs where several new compounds have entered clinical trials. In this review, we have examined the bioenergetics of various bacterial pathogens, highlighting the versatility of electron donor and acceptor utilisation and the modularity of electron transport chain components in bacteria. In addition to re-examining classical concepts, we explore new literature that reveals the intricacies of pathogen energetics, for example, how Salmonella enterica and Campylobacter jejuni exploit host and microbiota to derive powerful electron donors and sinks; the strategies Mycobacterium tuberculosis and Pseudomonas aeruginosa use to persist in lung tissues; and the importance of sodium energetics and electron bifurcation in the chemiosmotic anaerobe Fusobacterium nucleatum. A combination of physiological, biochemical, and pharmacological data suggests that, in addition to the clinically-approved target F1Fo-ATP synthase, NADH dehydrogenase type II, succinate dehydrogenase, hydrogenase, cytochrome bd oxidase, and menaquinone biosynthesis pathways are particularly promising next-generation drug targets. The realisation of cellular energetics as a rich target space for the development of new antimicrobials will be dependent upon gaining increased understanding of the energetic processes utilised by pathogens in host environments and the ability to design bacterial-specific inhibitors of these processes.
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Starosta AL, Lassak J, Jung K, Wilson DN. The bacterial translation stress response. FEMS Microbiol Rev 2014; 38:1172-201. [PMID: 25135187 DOI: 10.1111/1574-6976.12083] [Citation(s) in RCA: 134] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 07/18/2014] [Accepted: 08/07/2014] [Indexed: 11/30/2022] Open
Abstract
Throughout their life, bacteria need to sense and respond to environmental stress. Thus, such stress responses can require dramatic cellular reprogramming, both at the transcriptional as well as the translational level. This review focuses on the protein factors that interact with the bacterial translational apparatus to respond to and cope with different types of environmental stress. For example, the stringent factor RelA interacts with the ribosome to generate ppGpp under nutrient deprivation, whereas a variety of factors have been identified that bind to the ribosome under unfavorable growth conditions to shut-down (RelE, pY, RMF, HPF and EttA) or re-program (MazF, EF4 and BipA) translation. Additional factors have been identified that rescue ribosomes stalled due to stress-induced mRNA truncation (tmRNA, ArfA, ArfB), translation of unfavorable protein sequences (EF-P), heat shock-induced subunit dissociation (Hsp15), or antibiotic inhibition (TetM, FusB). Understanding the mechanism of how the bacterial cell responds to stress will not only provide fundamental insight into translation regulation, but will also be an important step to identifying new targets for the development of novel antimicrobial agents.
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Affiliation(s)
- Agata L Starosta
- Gene Center, Department for Biochemistry, Ludwig-Maximilians-Universität München, Munich, Germany; Center for integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität München, Munich, Germany
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18
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Condell O, Power KA, Händler K, Finn S, Sheridan A, Sergeant K, Renaut J, Burgess CM, Hinton JCD, Nally JE, Fanning S. Comparative analysis of Salmonella susceptibility and tolerance to the biocide chlorhexidine identifies a complex cellular defense network. Front Microbiol 2014; 5:373. [PMID: 25136333 PMCID: PMC4117984 DOI: 10.3389/fmicb.2014.00373] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Accepted: 07/03/2014] [Indexed: 12/04/2022] Open
Abstract
Chlorhexidine is one of the most widely used biocides in health and agricultural settings as well as in the modern food industry. It is a cationic biocide of the biguanide class. Details of its mechanism of action are largely unknown. The frequent use of chlorhexidine has been questioned recently, amidst concerns that an overuse of this compound may select for bacteria displaying an altered susceptibility to antimicrobials, including clinically important anti-bacterial agents. We generated a Salmonella enterica serovar Typhimurium isolate (ST24CHX) that exhibited a high-level tolerant phenotype to chlorhexidine, following several rounds of in vitro selection, using sub-lethal concentrations of the biocide. This mutant showed altered suceptibility to a panel of clinically important antimicrobial compounds. Here we describe a genomic, transcriptomic, proteomic, and phenotypic analysis of the chlorhexidine tolerant S. Typhimurium compared with its isogenic sensitive progenitor. Results from this study describe a chlorhexidine defense network that functions in both the reference chlorhexidine sensitive isolate and the tolerant mutant. The defense network involved multiple cell targets including those associated with the synthesis and modification of the cell wall, the SOS response, virulence, and a shift in cellular metabolism toward anoxic pathways, some of which were regulated by CreB and Fur. In addition, results indicated that chlorhexidine tolerance was associated with more extensive modifications of the same cellular processes involved in this proposed network, as well as a divergent defense response involving the up-regulation of additional targets such as the flagellar apparatus and an altered cellular phosphate metabolism. These data show that sub-lethal concentrations of chlorhexidine induce distinct changes in exposed Salmonella, and our findings provide insights into the mechanisms of action and tolerance to this biocidal agent.
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Affiliation(s)
- Orla Condell
- UCD Centre for Food Safety, School of Public Health, Physiotherapy and Population Science, University College Dublin Belfield, Dublin, Ireland ; European Program for Public Health Microbiology Training, European Centre for Disease Prevention and Control Stockholm, Sweden
| | - Karen A Power
- UCD Centre for Food Safety, School of Public Health, Physiotherapy and Population Science, University College Dublin Belfield, Dublin, Ireland
| | - Kristian Händler
- Department of Microbiology, School of Genetics and Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin Dublin, Ireland
| | - Sarah Finn
- UCD Centre for Food Safety, School of Public Health, Physiotherapy and Population Science, University College Dublin Belfield, Dublin, Ireland
| | - Aine Sheridan
- Food Safety Department, Teagasc Food Research Centre Ashtown, Dublin, Ireland
| | - Kjell Sergeant
- Department of Environment and Agrobiotechnologies (EVA), Centre de Recherche Public-Gabriel Lippmann Belvaux, Luxembourg
| | - Jenny Renaut
- Department of Environment and Agrobiotechnologies (EVA), Centre de Recherche Public-Gabriel Lippmann Belvaux, Luxembourg
| | - Catherine M Burgess
- Food Safety Department, Teagasc Food Research Centre Ashtown, Dublin, Ireland
| | - Jay C D Hinton
- Department of Microbiology, School of Genetics and Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin Dublin, Ireland ; Institute of Integrative Biology, University of Liverpool Liverpool, UK
| | - Jarlath E Nally
- School of Veterinary Medicine, University College Dublin Belfield, Dublin, Ireland
| | - Séamus Fanning
- UCD Centre for Food Safety, School of Public Health, Physiotherapy and Population Science, University College Dublin Belfield, Dublin, Ireland ; Institute for Global Food Security, Queen's University Belfast Belfast, Northern Ireland
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19
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Dahal N, Abdelhamed H, Lu J, Karsi A, Lawrence ML. Tricarboxylic acid cycle and one-carbon metabolism pathways are important in Edwardsiella ictaluri virulence. PLoS One 2013; 8:e65973. [PMID: 23762452 PMCID: PMC3676347 DOI: 10.1371/journal.pone.0065973] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Accepted: 04/29/2013] [Indexed: 11/24/2022] Open
Abstract
Edwardsiella ictaluri is a Gram-negative facultative intracellular pathogen causing enteric septicemia of channel catfish (ESC). The disease causes considerable economic losses in the commercial catfish industry in the United States. Although antibiotics are used as feed additive, vaccination is a better alternative for prevention of the disease. Here we report the development and characterization of novel live attenuated E. ictaluri mutants. To accomplish this, several tricarboxylic acid cycle (sdhC, mdh, and frdA) and one-carbon metabolism genes (gcvP and glyA) were deleted in wild type E. ictaluri strain 93-146 by allelic exchange. Following bioluminescence tagging of the E. ictaluri ΔsdhC, Δmdh, ΔfrdA, ΔgcvP, and ΔglyA mutants, their dissemination, attenuation, and vaccine efficacy were determined in catfish fingerlings by in vivo imaging technology. Immunogenicity of each mutant was also determined in catfish fingerlings. Results indicated that all of the E. ictaluri mutants were attenuated significantly in catfish compared to the parent strain as evidenced by 2,265-fold average reduction in bioluminescence signal from all the mutants at 144 h post-infection. Catfish immunized with the E. ictaluri ΔsdhC, Δmdh, ΔfrdA, and ΔglyA mutants had 100% relative percent survival (RPS), while E. ictaluri ΔgcvP vaccinated catfish had 31.23% RPS after re-challenge with the wild type E. ictaluri.
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Affiliation(s)
- Neeti Dahal
- Department of Basic Sciences, College of Veterinary Medicine Sciences, Mississippi State University, Mississippi State, Mississippi, United States of America
| | - Hossam Abdelhamed
- Department of Fish Diseases and Management, Faculty of Veterinary Medicine, Benha University, Moshtohor-Toukh, Egypt
| | - Jingjun Lu
- Department of Basic Sciences, College of Veterinary Medicine Sciences, Mississippi State University, Mississippi State, Mississippi, United States of America
| | - Attila Karsi
- Department of Basic Sciences, College of Veterinary Medicine Sciences, Mississippi State University, Mississippi State, Mississippi, United States of America
- * E-mail: (AK); (MLL)
| | - Mark L. Lawrence
- Department of Basic Sciences, College of Veterinary Medicine Sciences, Mississippi State University, Mississippi State, Mississippi, United States of America
- * E-mail: (AK); (MLL)
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20
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Neidig A, Yeung ATY, Rosay T, Tettmann B, Strempel N, Rueger M, Lesouhaitier O, Overhage J. TypA is involved in virulence, antimicrobial resistance and biofilm formation in Pseudomonas aeruginosa. BMC Microbiol 2013; 13:77. [PMID: 23570569 PMCID: PMC3639842 DOI: 10.1186/1471-2180-13-77] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Accepted: 04/04/2013] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Pseudomonas aeruginosa is an important opportunistic human pathogen and is extremely difficult to treat due to its high intrinsic and adaptive antibiotic resistance, ability to form biofilms in chronic infections and broad arsenal of virulence factors, which are finely regulated. TypA is a GTPase that has recently been identified to modulate virulence in enteric Gram-negative pathogens. RESULTS Here, we demonstrate that mutation of typA in P. aeruginosa resulted in reduced virulence in phagocytic amoebae and human macrophage models of infection. In addition, the typA mutant was attenuated in rapid cell attachment to surfaces and biofilm formation, and exhibited reduced antibiotic resistance to ß-lactam, tetracycline and antimicrobial peptide antibiotics. Quantitative RT-PCR revealed the down-regulation, in a typA mutant, of important virulence-related genes such as those involved in regulation and assembly of the Type III secretion system, consistent with the observed phenotypes and role in virulence of P. aeruginosa. CONCLUSIONS These data suggest that TypA is a newly identified modulator of pathogenesis in P. aeruginosa and is involved in multiple virulence-related characteristics.
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Affiliation(s)
- Anke Neidig
- Karlsruhe Institute of Technology (KIT), Institute of Functional Interfaces, PO Box 3640, Karlsruhe, 76021, Germany
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21
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Helaine S, Holden DW. Heterogeneity of intracellular replication of bacterial pathogens. Curr Opin Microbiol 2013; 16:184-91. [DOI: 10.1016/j.mib.2012.12.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 12/20/2012] [Accepted: 12/21/2012] [Indexed: 10/27/2022]
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22
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Horstman NK, Darwin AJ. Phage shock proteins B and C prevent lethal cytoplasmic membrane permeability in Yersinia enterocolitica. Mol Microbiol 2012; 85:445-60. [PMID: 22646656 DOI: 10.1111/j.1365-2958.2012.08120.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The bacterial phage shock protein (Psp) stress response system is activated by events affecting the cytoplasmic membrane. In response, Psp protein levels increase, including PspA, which has been implicated as the master effector of stress tolerance. Yersinia enterocolitica and related bacteria with a defective Psp system are highly sensitive to the mislocalization of pore-forming secretin proteins. However, why secretins are toxic to psp null strains, whereas some other Psp inducers are not, has not been explained. Furthermore, previous work has led to the confounding and disputable suggestion that PspA is not involved in mitigating secretin toxicity. Here we have established a correlation between the amount of secretin toxicity in a psp null strain and the extent of cytoplasmic membrane permeability to large molecules. This leads to a morphological change resembling cells undergoing plasmolysis. Furthermore, using novel strains with dis-regulated Psp proteins has allowed us to obtain unequivocal evidence that PspA is not required for secretin-stress tolerance. Together, our data suggest that the mechanism by which secretin multimers kill psp null cells is by causing a profound defect in the cytoplasmic membrane permeability barrier. This allows lethal molecular exchange with the environment, which the PspB and PspC proteins can prevent.
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Affiliation(s)
- N Kaye Horstman
- Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA
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23
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Selection of Salmonella enterica serovar Typhi genes involved during interaction with human macrophages by screening of a transposon mutant library. PLoS One 2012; 7:e36643. [PMID: 22574205 PMCID: PMC3344905 DOI: 10.1371/journal.pone.0036643] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Accepted: 04/04/2012] [Indexed: 12/21/2022] Open
Abstract
The human-adapted Salmonella enterica serovar Typhi (S. Typhi) causes a systemic infection known as typhoid fever. This disease relies on the ability of the bacterium to survive within macrophages. In order to identify genes involved during interaction with macrophages, a pool of approximately 105 transposon mutants of S. Typhi was subjected to three serial passages of 24 hours through human macrophages. Mutants recovered from infected macrophages (output) were compared to the initial pool (input) and those significantly underrepresented resulted in the identification of 130 genes encoding for cell membrane components, fimbriae, flagella, regulatory processes, pathogenesis, and many genes of unknown function. Defined deletions in 28 genes or gene clusters were created and mutants were evaluated in competitive and individual infection assays for uptake and intracellular survival during interaction with human macrophages. Overall, 26 mutants had defects in the competitive assay and 14 mutants had defects in the individual assay. Twelve mutants had defects in both assays, including acrA, exbDB, flhCD, fliC, gppA, mlc, pgtE, typA, waaQGP, SPI-4, STY1867-68, and STY2346. The complementation of several mutants by expression of plasmid-borne wild-type genes or gene clusters reversed defects, confirming that the phenotypic impairments within macrophages were gene-specific. In this study, 35 novel phenotypes of either uptake or intracellular survival in macrophages were associated with Salmonella genes. Moreover, these results reveal several genes encoding molecular mechanisms not previously known to be involved in systemic infection by human-adapted typhoidal Salmonella that will need to be elucidated.
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24
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Abstract
Hydrogen fuel is renewable, efficient and clean, and fermentative bacteria hold great promise for its generation. Here we use the isogenic Escherichia coli K‐12 KEIO library to rapidly construct multiple, precise deletions in the E. coli genome to direct the metabolic flux towards hydrogen production. Escherichia coli has three active hydrogenases, and the genes involved in the regulation of the formate hydrogen lyase (FHL) system for synthesizing hydrogen from formate via hydrogenase 3 were also manipulated to enhance hydrogen production. Specifically, we altered regulation of FHL by controlling the regulators HycA and FhlA, removed hydrogen consumption by hydrogenases 1 and 2 via the hyaB and hybC mutations, and re‐directed formate metabolism using the fdnG, fdoG, narG, focA, fnr and focB mutations. The result was a 141‐fold increase in hydrogen production from formate to create a bacterium (BW25113 hyaB hybC hycA fdoG/pCA24N‐FhlA) that produces the largest amount of hydrogen to date and one that achieves the theoretical yield for hydrogen from formate. In addition, the hydrogen yield from glucose was increased by 50%, and there was threefold higher hydrogen production from glucose with this strain.
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Affiliation(s)
- Toshinari Maeda
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843-3122, USA
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25
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Liu X, Rodermel SR, Yu F. A var2 leaf variegation suppressor locus, SUPPRESSOR OF VARIEGATION3, encodes a putative chloroplast translation elongation factor that is important for chloroplast development in the cold. BMC PLANT BIOLOGY 2010; 10:287. [PMID: 21187014 PMCID: PMC3022910 DOI: 10.1186/1471-2229-10-287] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Accepted: 12/28/2010] [Indexed: 05/18/2023]
Abstract
BACKGROUND The Arabidopsis var2 mutant displays a unique green and white/yellow leaf variegation phenotype and lacks VAR2, a chloroplast FtsH metalloprotease. We are characterizing second-site var2 genetic suppressors as means to better understand VAR2 function and to study the regulation of chloroplast biogenesis. RESULTS In this report, we show that the suppression of var2 variegation in suppressor line TAG-11 is due to the disruption of the SUPPRESSOR OF VARIEGATION3 (SVR3) gene, encoding a putative TypA-like translation elongation factor. SVR3 is targeted to the chloroplast and svr3 single mutants have uniformly pale green leaves at 22°C. Consistent with this phenotype, most chloroplast proteins and rRNA species in svr3 have close to normal accumulation profiles, with the notable exception of the Photosystem II reaction center D1 protein, which is present at greatly reduced levels. When svr3 is challenged with chilling temperature (8°C), it develops a pronounced chlorosis that is accompanied by abnormal chloroplast rRNA processing and chloroplast protein accumulation. Double mutant analysis indicates a possible synergistic interaction between svr3 and svr7, which is defective in a chloroplast pentatricopeptide repeat (PPR) protein. CONCLUSIONS Our findings, on one hand, reinforce the strong genetic link between VAR2 and chloroplast translation, and on the other hand, point to a critical role of SVR3, and possibly some aspects of chloroplast translation, in the response of plants to chilling stress.
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Affiliation(s)
- Xiayan Liu
- College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, People's Republic of China
| | - Steve R Rodermel
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA
| | - Fei Yu
- College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, People's Republic of China
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26
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Micklinghoff JC, Schmidt M, Geffers R, Tegge W, Bange FC. Analysis of expression and regulatory functions of the ribosome-binding protein TypA in Mycobacterium tuberculosis under stress conditions. Arch Microbiol 2010; 192:499-504. [PMID: 20437167 DOI: 10.1007/s00203-010-0571-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Revised: 03/10/2010] [Accepted: 03/25/2010] [Indexed: 11/29/2022]
Abstract
In many bacterial species, the translational GTPase TypA acts as a global stress- and virulence regulator and also mediates resistance to the antimicrobial peptide BPI. On the chromosome of M. tuberculosis, typA is located next to narGHJI, which plays a role in adaptation of the pathogen to various environmental conditions. Here, we show that Mycobacterium tuberculosis is sensitive to P2, a derivative of BPI. Using a typA mutant of M. tuberculosis, we found this phenotype to be independent of TypA. We further tested typA expression in M. tuberculosis under defined stress conditions, such as oxygen- and nutrient depletion, low pH, heat shock, antibiotic stress and the presence of P2, and found that typA expression remains unaffected by any of these conditions. Analysis of growth and whole-genome expression revealed similar growth kinetics and gene expression profiles of the wild type and the mutant under normal growth conditions as well as under stress conditions. Our results suggest that in contrast to the findings in other bacteria, TypA does not act as a global stress- and virulence regulator in M. tuberculosis.
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Affiliation(s)
- Julia C Micklinghoff
- Department of Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
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27
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Abstract
Human beta-defensin 3 (hBD3) is a highly charged (+11) cationic host defense peptide, produced by epithelial cells and neutrophils. hBD3 retains antimicrobial activity against a broad range of pathogens, including multiresistant Staphylococcus aureus, even under high-salt conditions. Whereas antimicrobial host defense peptides are assumed to act by permeabilizing cell membranes, the transcriptional response pattern of hBD3-treated staphylococcal cells resembled that of vancomycin-treated cells (V. Sass, U. Pag, A. Tossi, G. Bierbaum, and H. G. Sahl, Int. J. Med. Microbiol. 298:619-633, 2008) and suggested that inhibition of cell wall biosynthesis is a major component of the killing process. hBD3-treated cells, inspected by transmission electron microscopy, showed localized protrusions of cytoplasmic contents, and analysis of the intracellular pool of nucleotide-activated cell wall precursors demonstrated accumulation of the final soluble precursor, UDP-MurNAc-pentapeptide. Accumulation is typically induced by antibiotics that inhibit membrane-bound steps of cell wall biosynthesis and also demonstrates that hBD3 does not impair the biosynthetic capacity of cells and does not cause gross leakage of small cytoplasmic compounds. In in vitro assays of individual membrane-associated cell wall biosynthesis reactions (MraY, MurG, FemX, and penicillin-binding protein 2 [PBP2]), hBD3 inhibited those enzymes which use the bactoprenol-bound cell wall building block lipid II as a substrate; quantitative analysis suggested that hBD3 may stoichiometrically bind to lipid II. We report that binding of hBD3 to defined, lipid II-rich sites of cell wall biosynthesis may lead to perturbation of the biosynthesis machinery, resulting in localized lesions in the cell wall as demonstrated by electron microscopy. The lesions may then allow for osmotic rupture of cells when defensins are tested under low-salt conditions.
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28
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Translation factor LepA contributes to tellurite resistance in Escherichia coli but plays no apparent role in the fidelity of protein synthesis. Biochimie 2009; 92:157-63. [PMID: 19925844 DOI: 10.1016/j.biochi.2009.11.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2009] [Accepted: 11/11/2009] [Indexed: 11/23/2022]
Abstract
LepA is a translational GTPase highly conserved in bacterial lineages. While it has been shown that LepA can catalyze reverse ribosomal translocation in vitro, the role of LepA in the cell remains unclear. Here, we show that deletion of the lepA gene (DeltalepA) in Escherichia coli causes hypersensitivity to potassium tellurite and penicillin G, but has no appreciable effect on growth under many other conditions. DeltalepA does not increase miscoding or frameshifting errors under normal or stress conditions, indicating that LepA does not contribute to the fidelity of translation. Overexpression of LepA interferes with tmRNA-mediated peptide tagging and A-site mRNA cleavage, suggesting that LepA is a bona fide translation factor that can act on stalled ribosomes with a vacant A site in vivo. Together these results lead us to hypothesize that LepA is involved in co-translational folding of proteins that are otherwise vulnerable to tellurite oxidation.
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29
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deLivron MA, Makanji HS, Lane MC, Robinson VL. A novel domain in translational GTPase BipA mediates interaction with the 70S ribosome and influences GTP hydrolysis. Biochemistry 2009; 48:10533-41. [PMID: 19803466 DOI: 10.1021/bi901026z] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BipA is a universally conserved prokaryotic GTPase that exhibits differential ribosome association in response to stress-related events. It is a member of the translation factor family of GTPases along with EF-G and LepA. BipA has five domains. The N-terminal region of the protein, consisting of GTPase and beta-barrel domains, is common to all translational GTPases. BipA domains III and V have structural counterparts in EF-G and LepA. However, the C-terminal domain (CTD) of the protein is unique to the BipA family. To investigate how the individual domains of BipA contribute to the biological properties of the protein, deletion constructs were designed and their GTP hydrolysis and ribosome binding properties assessed. Data presented show that removal of the CTD abolishes the ability of BipA to bind to the ribosome and that ribosome complex formation requires the surface provided by domains III and V and the CTD. Additional mutational analysis was used to outline the BipA-70S interaction surface extending across these domains. Steady state kinetic analyses revealed that successive truncation of domains from the C-terminus resulted in a significant increase in the intrinsic GTP hydrolysis rate and a loss of ribosome-stimulated GTPase activity. These results indicate that, similar to other translational GTPases, the ribosome binding and GTPase activities of BipA are tightly coupled. Such intermolecular regulation likely plays a role in the differential ribosome binding by the protein.
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Affiliation(s)
- Megan A deLivron
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269, USA
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30
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High-throughput bioluminescence-based mutant screening strategy for identification of bacterial virulence genes. Appl Environ Microbiol 2009; 75:2166-75. [PMID: 19201969 DOI: 10.1128/aem.02449-08] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
A high-throughput bioluminescence screening procedure for identification of virulence genes in bacteria was developed and applied to the fish pathogen Edwardsiella ictaluri. A random transposon mutant library expressing bioluminescence was constructed and robotically arrayed on 384-well plates. Mutants were cultivated and mixed with catfish serum and neutrophils in 96-well plates, and bioluminescence was used to detect mutants that are more susceptible to killing by these host factors. The virulence and vaccine efficacy of selected mutants were determined in channel catfish. Transposon insertion sites in 13 mutants attenuated in the natural host were mapped to the E. ictaluri genome. Ten unique genes were mutated, including genes encoding a negative regulator of sigmaE activity, a glycine cleavage system protein, tricarboxylic acid cycle enzymes, an O polysaccharide biosynthesis enzyme, proteins encoded on the native plasmid pEI1, and a fimbrial chaperon protein. Three of these mutants were found to have potential as live attenuated vaccines. This study demonstrates a novel application of bioluminescence to identify bacterial genes required for host resistance; as a result, efficacious and genetically defined live attenuated vaccine candidates were developed.
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Barchiesi J, Espariz M, Checa SK, Soncini FC. Downregulation of RpoN-controlled genes protects Salmonella cells from killing by the cationic antimicrobial peptide polymyxin B. FEMS Microbiol Lett 2008; 291:73-9. [PMID: 19076233 DOI: 10.1111/j.1574-6968.2008.01437.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Salmonella enterica polymyxin B (PM) resistance is modulated mainly by substitutions of the acyl chains and the phosphate groups on the lipid A moiety of lipopolysaccharide. These modifications are mediated by genes under the control of the PmrA/PmrB and PhoP/PhoQ two-component regulatory systems. In this study, a deletion in the gene encoding the alternative sigma(54) factor, rpoN, was shown to increase PM resistance without affecting protamine sensitivity. The results presented here showed that the increased polymyxin resistance observed in the DeltarpoN mutant occurs through a PmrA/PhoP-independent pathway. Downregulation of one or more genes belonging to the RpoN regulon may provide an additional mechanism of defence against membrane-permeabilizing antimicrobial peptides that helps the pathogen to survive in different environments.
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Affiliation(s)
- Julieta Barchiesi
- Departamento de Microbiología, Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
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Duo M, Hou S, Ren D. Identifying Escherichia coli genes involved in intrinsic multidrug resistance. Appl Microbiol Biotechnol 2008; 81:731-41. [DOI: 10.1007/s00253-008-1709-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Revised: 07/29/2008] [Accepted: 09/04/2008] [Indexed: 10/21/2022]
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Suppression of DeltabipA phenotypes in Escherichia coli by abolishment of pseudouridylation at specific sites on the 23S rRNA. J Bacteriol 2008; 190:7675-83. [PMID: 18820021 DOI: 10.1128/jb.00835-08] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The BipA protein of Escherichia coli has intriguing similarities to the elongation factor subfamily of GTPases, including EF-Tu, EF-G, and LepA. In addition, phenotypes of a bipA deletion mutant suggest that BipA is involved in regulation of a variety of pathways. These two points have led to speculation that BipA may be a novel regulatory protein that affects efficient translation of target genes through direct interaction with the ribosome. We isolated and characterized suppressors of the cold-sensitive growth phenotype exhibited by DeltabipA strains and identified insertion mutations in rluC. The rluC gene encodes a pseudouridine synthase responsible for pseudouridine modification of 23S rRNA at three sites, all located near the peptidyl transferase center. Deletion of rluC not only suppressed cold sensitivity but also alleviated the decrease in capsule synthesis exhibited by bipA mutants, suggesting that the phenotypic effects of BipA are manifested through an effect on the ribosome. The suppressor effect is specific to rluC, as deletion of other rlu genes did not relieve cold sensitivity, and further, more than a single pseudouridine residue is involved, as alteration of single residues did not produce suppressors. These results are consistent with a role for BipA in either the structure or the function of the ribosome and imply that wild-type ribosomes are dependent on BipA for efficient expression of target mRNAs and that the lack of pseudouridylation at these three sites renders the ribosomes BipA independent.
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Salmonella enterica serovar Typhimurium BipA exhibits two distinct ribosome binding modes. J Bacteriol 2008; 190:5944-52. [PMID: 18621905 DOI: 10.1128/jb.00763-08] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
BipA is a highly conserved prokaryotic GTPase that functions to influence numerous cellular processes in bacteria. In Escherichia coli and Salmonella enterica serovar Typhimurium, BipA has been implicated in controlling bacterial motility, modulating attachment and effacement processes, and upregulating the expression of virulence genes and is also responsible for avoidance of host defense mechanisms. In addition, BipA is thought to be involved in bacterial stress responses, such as those associated with virulence, temperature, and symbiosis. Thus, BipA is necessary for securing bacterial survival and successful invasion of the host. Steady-state kinetic analysis and pelleting assays were used to assess the GTPase and ribosome-binding properties of S. enterica BipA. Under normal bacterial growth, BipA associates with the ribosome in the GTP-bound state. However, using sucrose density gradients, we demonstrate that the association of BipA and the ribosome is altered under stress conditions in bacteria similar to those experienced during virulence. The data show that this differential binding is brought about by the presence of ppGpp, an alarmone that signals the onset of stress-related events in bacteria.
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Calvó L, Martínez-Planells A, Pardos-Bosch J, Garcia-Gil LJ. A New Real-Time PCR Assay for the Specific Detection of Salmonella spp. Targeting the bipA Gene. FOOD ANAL METHOD 2008. [DOI: 10.1007/s12161-007-9008-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Pag U, Oedenkoven M, Sass V, Shai Y, Shamova O, Antcheva N, Tossi A, Sahl HG. Analysis of in vitro activities and modes of action of synthetic antimicrobial peptides derived from an alpha-helical 'sequence template'. J Antimicrob Chemother 2008; 61:341-52. [PMID: 18174202 DOI: 10.1093/jac/dkm479] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES Cationic antimicrobial peptides (AMPs) are indispensable components of innate immune systems and promising candidates for novel anti-infective strategies. We rationally designed a series of peptides based on a template derived from known alpha-helical AMPs, which were then analysed regarding efficacy against clinical isolates and antibiotic mechanisms. METHODS Efficacy tests included standard MIC and synergy assays. Whole cell assays with staphylococcal strains included killing kinetics, efflux experiments and determination of membrane depolarization. The transcriptional response of AMP-treated Staphylococcus aureus SG511 was analysed using a Scienion genomic microarray covering (approximately 90% of) the S. aureus N315 genome and AMP P16(6|E). RESULTS The AMPs showed remarkable broad-spectrum activity against bacteria and fungi regardless of any pre-existing antibiotic resistance mechanism. Whole cell assays indicated that the AMPs target the cytoplasmic membrane; however, significant membrane leakage and depolarization was only observed with a standard laboratory test strain. Transcriptional profiling identified up-regulation of putative efflux pumps and of aerobic energy generation mechanisms as major counter activities. Important components of the staphylococcal cell wall stress stimulon were up-regulated and the lipid metabolism was also affected. CONCLUSIONS The broad spectrum activity of amphiphilic helical AMPs is based on multiple stresses resulting from interactions with microbial membranes; however, rather than killing through formation of pores, the AMPs appear to interfere with the coordinated and highly dynamic functioning of membrane bound multienzyme complexes such as electron transport chains and cell wall or lipid biosynthesis machineries.
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Affiliation(s)
- U Pag
- Institute for Medical Microbiology, Immunology and Parasitology-Pharmaceutical Microbiology Section, University of Bonn, 53105 Bonn, Germany
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Beier RC, Hume ME, Anderson RC, Oliver CE, Callaway TR, Edrington TS, Nisbet DJ. HPLC determination of chlorate metabolism in bovine ruminal fluid. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART. B, PESTICIDES, FOOD CONTAMINANTS, AND AGRICULTURAL WASTES 2007; 42:717-26. [PMID: 17701707 DOI: 10.1080/03601230701544967] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Salmonella and Escherichia coli are two bacteria that are important causes of human and animal disease worldwide. Chlorate is converted in the cell to chlorite, which is lethal to these bacteria. An HPLC procedure was developed for the rapid analysis of chlorate (ClO(3)(-)), nitrate (NO(3)(-)), and nitrite (NO(2)(-)) ions in bovine ruminal fluid samples. Standard curves for chlorite, nitrite, nitrate, and chlorate were well defined linear curves with R(2) values of 0.99846, 0.99106, 0.99854, and 0.99138, respectively. Concentrations of chlorite could not be accurately determined in bovine ruminal fluid because chlorite reacts with or binds a component(s) or is reduced to chloride in bovine ruminal fluid resulting in low chlorite measurements. A standard curve ranging from 25 to 150 ppm ClO(3)(-) ion was used to measure chlorate fortified into ruminal fluid. The concentration of chlorate was more rapidly lowered (P < 0.01) under anaerobic compared to aerobic incubation conditions. Chlorate alone or chlorate supplemented with the reductants sodium lactate or glycerol were bactericidal in anaerobic incubations. In anaerobic culture, the addition of sodium formate to chlorate-fortified ruminal fluid appeared to decrease chlorate concentrations; however, formate also appeared to moderate the bactericidal effect of chlorate against E. coli. Addition of the reductants, glycerol or lactate, to chlorate-fortified ruminal fluid did not increase the killing of E. coli at 24 h, but may be useful when the reducing equivalents are limiting as in waste holding reservoirs or composting systems required for intense animal production.
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Affiliation(s)
- Ross C Beier
- Southern Plains Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, College Station, TX, USA.
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Abstract
Antimicrobial host defense peptides constitute a major component of innate immune systems. Expectations are high to develop them into a novel class of anti-infective agents. In this issue of Chemistry & Biology, Hilpert et al. describe new design and peptide synthesis strategies for systematically investigating such concepts.
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Affiliation(s)
- Hans Georg Sahl
- University of Bonn, Institute for Medical Microbiology, Immunology and Parasitology, Pharmaceutical Microbiology Unit, Meckenheimer Allee 168, 53115 Bonn, Germany
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Bryksa BC, MacDonald LD, Patrzykat A, Douglas SE, Mattatall NR. A C-terminal glycine suppresses production of pleurocidin as a fusion peptide in Escherichia coli. Protein Expr Purif 2006; 45:88-98. [PMID: 15935695 DOI: 10.1016/j.pep.2005.04.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Accepted: 04/19/2005] [Indexed: 11/25/2022]
Abstract
The winter flounder (Pseudopleuronectes americanus) antimicrobial peptide pleurocidin was produced in Escherichia coli using a synthetic gene constructed by PCR. The gene expresses pleurocidin from pET21a fused to the C-terminus of an insoluble carrier peptide. Once expressed, the fusion peptide formed inclusion bodies in the cytoplasm that were collected, solubilized in guanidine-HCl, and chemically cleaved using hydroxylamine at a unique asparaginyl-glycyl dipeptide. This released recombinant pleurocidin (r-pleurocidin), which was purified using ultrafiltration followed by reverse phase chromatography. The r-pleurocidin peptide resolved as a single band (2.7 kDa) when analyzed by Tris-Tricine buffered SDS-PAGE, and its amino acid sequence was confirmed using tandem mass spectrometry. Extending the pleurocidin sequence with a C-terminal glycine (r-pleurocidin-G) suppressed production of the fusion peptide 15-fold. When pleurocidin was extended further to include aspartate (r-pleurocidin-GD), the same effect was observed, and when pleurocidin was extended with aspartate alone, no effect was observed. Expression of fusion peptide containing either r-pleurocidin-G or r-pleurocidin-GD with low concentrations of inductant caused E. coli to enter stationary phase prematurely, but did not affect overall growth rates. A partial production recovery of r-pleurocidin-G was achieved by inducing expression in stationary phase cells. We observed r-pleurocidin-G to have enhanced antimicrobial activity compared with r-pleurocidin, and we propose that this activity interferes with E. coli metabolism during expression. This antimicrobial effect is probably facilitated by residual solubility of the fusion peptide and by a C-terminal cap structure, which stabilizes the r-pleurocidin-G alpha-helix that is thought to be important for activity.
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Affiliation(s)
- Brian C Bryksa
- NRC Institute for Marine Biosciences, National Research Council Canada, Halifax, NS, Canada B3H 3Z1
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40
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Becker LA, Bang IS, Crouch ML, Fang FC. Compensatory role of PspA, a member of the phage shock protein operon, in rpoE mutant Salmonella enterica serovar Typhimurium. Mol Microbiol 2005; 56:1004-16. [PMID: 15853886 DOI: 10.1111/j.1365-2958.2005.04604.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sigma(E) is an alternative sigma factor that responds to and ameliorates extracytoplasmic stress. In Salmonella enterica serovar Typhimurium (S. Typhimurium), sigma(E) is required for oxidative stress resistance, stationary-phase survival and virulence in mice. Microarray analysis of stationary-phase gene expression in rpoE mutant bacteria revealed a dramatic increase in expression of pspA, a member of the phage shock protein (psp) operon. The psp operon can be induced by filamentous bacteriophages or by perturbations of protein secretion, and is believed to facilitate the maintenance of proton motive force (PMF). We hypothesized that increased pspA expression may represent a compensatory response to the loss of sigma(E) function. Increased pspA expression was confirmed in rpoE mutant Salmonella and also observed in a mutant lacking the F(1)F(0) ATPase. Alternatively, expression of pspA could be induced by exposure to CCCP, a protonophore that disrupts PMF. An rpoE pspA double mutant strain was found to have a stationary-phase survival defect more pronounced than that of isogenic strains harbouring single mutations. The double mutant strains were also more susceptible to killing by CCCP or by a bactericidal/permeability-increasing protein (BPI)-derived anti-microbial peptide. Using fluorescence ratio imaging, differences were observed in the Deltapsi of wild-type and rpoE or pspA mutant bacteria. These findings suggest that pspA expression in S. Typhimurium is induced by alterations in PMF and a functional sigma(E) regulon is essential for the maintenance of PMF.
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Affiliation(s)
- Lynne A Becker
- Departments of Laboratory Medicine and Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
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41
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Onufryk C, Crouch ML, Fang FC, Gross CA. Characterization of six lipoproteins in the sigmaE regulon. J Bacteriol 2005; 187:4552-61. [PMID: 15968066 PMCID: PMC1151791 DOI: 10.1128/jb.187.13.4552-4561.2005] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Escherichia coli, sigma(E) regulon functions are required for envelope homeostasis during stress and are essential for viability under all growth conditions. The E. coli genome encodes approximately 100 lipoproteins, and 6 of these are regulated by sigma(E). Phenotypes associated with deletion of each of these lipoproteins are the subject of this report. One lipoprotein, YfiO, is essential for cellular viability. However, overexpression of this protein is not sufficient to alleviate the requirement of sigma(E) for viability, suggesting that the sigma(E) regulon provides more than one essential function. The remaining five lipoproteins in the sigma(E) regulon are nonessential; cells are viable even when all five are removed simultaneously. Deletion of three nonessential lipoprotein genes (nlpB, yraP, ygfL) results in the exhibition of phenotypes that suggest they are important for maintenance of the integrity of the cell envelope. deltanlpB cells are selectively sensitive to rifampin; deltayraP cells are selectively sensitive to sodium dodecyl sulfate. Such selective sensitivity has not been previously reported. Both deltayraP and deltanlpB are synthetically lethal with surA::Cm, which encodes a periplasmic chaperone and PPIase, suggesting that NlpB and YraP play roles in a periplasmic folding pathway that functions in parallel with that of SurA. Finally, the deltayfgL mutant exhibits a broad range of envelope defects, including sensitivity to several membrane-impermeable agents, an altered outer membrane protein profile, synthetic lethality with both surA::Cm and deltafkpA::Cm strains, and sensitivity to a bactericidal permeability-increasing peptide. We suggest that this lipoprotein performs a very important but as-yet-unknown function in maintaining the integrity of the cell envelope.
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Affiliation(s)
- Christina Onufryk
- Department of Biochemistry & Biophysics, University of California, San Francisco, California 94143, USA
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42
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Rychlik I, Barrow PA. Salmonella stress management and its relevance to behaviour during intestinal colonisation and infection. FEMS Microbiol Rev 2005; 29:1021-40. [PMID: 16023758 DOI: 10.1016/j.femsre.2005.03.005] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2004] [Revised: 03/04/2005] [Accepted: 03/30/2005] [Indexed: 01/13/2023] Open
Abstract
The enteric pathogen Salmonella enterica is exposed to a number of stressful environments during its life cycle within and outside its various hosts. During intestinal colonisation Salmonella is successively exposed to acid pH in the stomach, to the detergent-like activity of bile, to decreasing oxygen supply, to the presence of multiple metabolites produced by the normal gut microflora and finally it is exposed to cationic antimicrobial peptides present on the surface of epithelial cells. There are four major regulators controlling relevant stress responses in Salmonella, namely RpoS, PhoPQ, Fur and OmpR/EnvZ. Except for Fur, inactivation of genes encoding the other stress regulators results in attenuated virulence and such mutants can therefore be considered as vaccine candidates. In contrast, a decrease in oxygen supply monitored by Fnr and ArcAB, or oxidative stress controlled by OxyR and SoxRS is not regarded as a stress associated with host colonisation since inactivation of either of these systems does not result in reductions in colonisation. The role of quorum-sensing through luxS and sdiA is also considered as a regulator of virulence and colonisation.
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Affiliation(s)
- Ivan Rychlik
- Veterinary Research Institute, Hudcova 70, 621 32 Brno, Czech Republic.
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Crouch ML, Becker LA, Bang IS, Tanabe H, Ouellette AJ, Fang FC. The alternative sigma factor σEis required for resistance ofSalmonella entericaserovar Typhimurium to anti-microbial peptides. Mol Microbiol 2005; 56:789-99. [PMID: 15819632 DOI: 10.1111/j.1365-2958.2005.04578.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The enteric pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium) encounters a variety of anti-microbial peptides during the course of infection. We report here that the extracytoplasmic sigma factor sigma(E) (RpoE) is required for Salmonella resistance to killing by the bactericidal/permeability-increasing protein (BPI)-derived peptide P2 and the murine alpha-defensin cryptdin-4 (Crp4). Moreover, sigma(E)-deficient S. Typhimurium is attenuated for virulence after oral infection of immunocompromised gp91phox(-/-) mice that lack a functional NADPH phagocyte oxidase, suggesting that sigma(E) plays an important role in resistance to non-oxidative mucosal host defences such as anti-microbial peptides. Although both P2 and Crp4 target the cell envelope, bacterial killing by these peptides appears to occur by distinct mechanisms. Formate enhances bacterial resistance to P2, as previously demonstrated, but not to Crp4. Both sigma(E) and cytoplasmic membrane-associated formate dehydrogenase are required for the protective effect of formate against P2. In contrast to P2, Crp4 does not inhibit bacterial respiration at lethal concentrations. However, both peptides induce expression of rpoE, suggesting that they trigger a common mechanism for sensing extracytoplasmic stress.
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Affiliation(s)
- Marie-Laure Crouch
- Department of Laboratory Medicine, Universit of Washington School of Medicine, Seattle, WA 98195, USA
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Rengby O, Johansson L, Carlson LA, Serini E, Vlamis-Gardikas A, Kårsnäs P, Arnér ESJ. Assessment of production conditions for efficient use of Escherichia coli in high-yield heterologous recombinant selenoprotein synthesis. Appl Environ Microbiol 2004; 70:5159-67. [PMID: 15345395 PMCID: PMC520894 DOI: 10.1128/aem.70.9.5159-5167.2004] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2004] [Accepted: 05/13/2004] [Indexed: 11/20/2022] Open
Abstract
The production of heterologous selenoproteins in Escherichia coli necessitates the design of a secondary structure in the mRNA forming a selenocysteine insertion sequence (SECIS) element compatible with SelB, the elongation factor for selenocysteine insertion at a predefined UGA codon. SelB competes with release factor 2 (RF2) catalyzing translational termination at UGA. Stoichiometry between mRNA, the SelB elongation factor, and RF2 is thereby important, whereas other expression conditions affecting the yield of recombinant selenoproteins have been poorly assessed. Here we expressed the rat selenoprotein thioredoxin reductase, with titrated levels of the selenoprotein mRNA under diverse growth conditions, with or without cotransformation of the accessory bacterial selA, selB, and selC genes. Titration of the selenoprotein mRNA with a pBAD promoter was performed in both TOP10 and BW27783 cells, which unexpectedly could not improve yield or specific activity compared to that achieved in our prior studies. Guided by principal component analysis, we instead discovered that the most efficient bacterial selenoprotein production conditions were obtained with the high-transcription T7lac-driven pET vector system in presence of the selA, selB, and selC genes, with induction of production at late exponential phase. About 40 mg of rat thioredoxin reductase with 50% selenocysteine content could thereby be produced per liter bacterial culture. These findings clearly illustrate the ability of E. coli to upregulate the selenocysteine incorporation machinery on demand and that this is furthermore strongly augmented in late exponential phase. This study also demonstrates that E. coli can indeed be utilized as cell factories for highly efficient production of heterologous selenoproteins such as rat thioredoxin reductase.
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Affiliation(s)
- Olle Rengby
- Medical Nobel Institute for Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institute, 171 77 Stockholm, Sweden
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Owens RM, Pritchard G, Skipp P, Hodey M, Connell SR, Nierhaus KH, O'Connor CD. A dedicated translation factor controls the synthesis of the global regulator Fis. EMBO J 2004; 23:3375-85. [PMID: 15297874 PMCID: PMC514516 DOI: 10.1038/sj.emboj.7600343] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2004] [Accepted: 07/05/2004] [Indexed: 11/09/2022] Open
Abstract
BipA is a highly conserved protein with global regulatory properties in Escherichia coli. We show here that it functions as a translation factor that is required specifically for the expression of the transcriptional modulator Fis. BipA binds to ribosomes at a site that coincides with that of elongation factor G and has a GTPase activity that is sensitive to high GDP:GTP ratios and stimulated by 70S ribosomes programmed with mRNA and aminoacylated tRNAs. The growth rate-dependent induction of BipA allows the efficient expression of Fis, thereby modulating a range of downstream processes, including DNA metabolism and type III secretion. We propose a model in which BipA destabilizes unusually strong interactions between the 5' untranslated region of fis mRNA and the ribosome. Since BipA spans phylogenetic domains, transcript-selective translational control for the 'fast-track' expression of specific mRNAs may have wider significance.
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Affiliation(s)
- Róisín M Owens
- School of Biological Sciences, University of Southampton, Southampton, UK
- Max-Planck-Institut für Molekulare Genetik, Berlin, Germany
| | - Gareth Pritchard
- School of Biological Sciences, University of Southampton, Southampton, UK
| | - Paul Skipp
- School of Biological Sciences, University of Southampton, Southampton, UK
- Centre for Proteomic Research, University of Southampton, Southampton, UK
| | - Michelle Hodey
- School of Biological Sciences, University of Southampton, Southampton, UK
| | - Sean R Connell
- Max-Planck-Institut für Molekulare Genetik, Berlin, Germany
| | | | - C David O'Connor
- School of Biological Sciences, University of Southampton, Southampton, UK
- Centre for Proteomic Research, University of Southampton, Southampton, UK
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46
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Riva A, Delorme MO, Chevalier T, Guilhot N, Hénaut C, Hénaut A. Characterization of the GATC regulatory network in E. coli. BMC Genomics 2004; 5:48. [PMID: 15265237 PMCID: PMC493266 DOI: 10.1186/1471-2164-5-48] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2004] [Accepted: 07/20/2004] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND The tetranucleotide GATC is methylated in Escherichia. coli by the DNA methyltransferase (Dam) and is known to be implicated in numerous cellular processes. Mutants lacking Dam are characterized by a pleiotropic phenotype. The existence of a GATC regulated network, thought to be involved in cold and oxygen shift, had been proposed and its existence has recently been confirmed. The aim of this article is to describe the components of the GATC regulated network of E. coli in detail and propose a role of this network in the light of an evolutionary advantage for the organism. RESULTS We have classified the genes of the GATC network according to the EcoCyc functional classes. Comparisons with all of E. coli's genes and the genes involved in the SOS and stress response show that the GATC network forms a group apart. The functional classes that characterize the network are the Energy metabolism (in particular respiration), Fatty acid/ Phospholipid metabolism and Nucleotide metabolism. CONCLUSIONS The network is thought to come into play when the cell undergoes coldshock and is likely to enter stationary phase.The respiration is almost completely under GATC control and according to our hypothesis it will be blocked at the moment of coldshock; this might give the cell a selective advantage as it increases its chances for survival when entering stationary phase under coldshock. We predict the accumulation of formate and possibly succinate, which might increase the cell's resistance, in this case to antimicrobial agents, when entering stationary phase.
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Affiliation(s)
- Alessandra Riva
- Laboratoire Génome et Informatique, UMR 8116, CNRS – Université d'Evry Val d'Essonne, Tour Evry 2, 523 Place des Terrasses, 91034 Evry cedex, France
| | - Marie-Odile Delorme
- Laboratoire Génome et Informatique, UMR 8116, CNRS – Université d'Evry Val d'Essonne, Tour Evry 2, 523 Place des Terrasses, 91034 Evry cedex, France
- Previous address: Hong Kong University- Pasteur Research Centre Ltd, Dexter HC Man Building, 8 Sassoon Road, Pokfulam, Hong Kong
| | - Tony Chevalier
- METabolic EXplorer S.A., Biop ô le Clermont-Limagne, 63 360 Saint-Beauzire, France
| | - Nicolas Guilhot
- METabolic EXplorer S.A., Biop ô le Clermont-Limagne, 63 360 Saint-Beauzire, France
| | - Corinne Hénaut
- METabolic EXplorer S.A., Biop ô le Clermont-Limagne, 63 360 Saint-Beauzire, France
| | - Alain Hénaut
- Laboratoire Génome et Informatique, UMR 8116, CNRS – Université d'Evry Val d'Essonne, Tour Evry 2, 523 Place des Terrasses, 91034 Evry cedex, France
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Mathur J, Waldor MK. The Vibrio cholerae ToxR-regulated porin OmpU confers resistance to antimicrobial peptides. Infect Immun 2004; 72:3577-83. [PMID: 15155667 PMCID: PMC415678 DOI: 10.1128/iai.72.6.3577-3583.2004] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
BPI (bactericidal/permeability-increasing) is a potent antimicrobial protein that was recently reported to be expressed as a surface protein on human gastrointestinal tract epithelial cells. In this study, we investigated the resistance of Vibrio cholerae, a small-bowel pathogen that causes cholera, to a BPI-derived peptide, P2. Unlike in Escherichia coli and Salmonella enterica serovar Typhimurium, resistance to P2 in V. cholerae was not dependent on the BipA GTPase. Instead, we found that ToxR, the master regulator of V. cholerae pathogenicity, controlled resistance to P2 by regulating the production of the outer membrane protein OmpU. Both toxR and ompU mutants were at least 100-fold more sensitive to P2 than were wild-type cells. OmpU also conferred resistance to polymyxin B sulfate, suggesting that this porin may impart resistance to cationic antibacterial proteins via a common mechanism. Studies of stationary-phase cells revealed that the ToxR-repressed porin OmpT may also contribute to P2 resistance. Finally, although the mechanism of porin-mediated resistance to antimicrobial peptides remains elusive, our data suggest that the BPI peptide sensitivity of OmpU-deficient V. cholerae is not attributable to a generally defective outer membrane.
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Affiliation(s)
- Jyoti Mathur
- Department of Immunology, Sackler School of Biomedical Sciences, Tufts University School of Medicine, and Howard Hughes Medical Institute, Boston, Massachusetts 02111, USA
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Grant AJ, Farris M, Alefounder P, Williams PH, Woodward MJ, O'Connor CD. Co-ordination of pathogenicity island expression by the BipA GTPase in enteropathogenic Escherichia coli (EPEC). Mol Microbiol 2003; 48:507-21. [PMID: 12675808 DOI: 10.1046/j.1365-2958.2003.t01-1-03447.x] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BipA is a novel member of the ribosome binding GTPase superfamily and is widely distributed in bacteria and plants. We report here that it regulates -multiple cell surface- and virulence-associated -components in the enteropathogenic Escherichia coli (EPEC) strain E2348/69. The regulated components include bacterial flagella, the espC pathogenicity island and a type III secretion system specified by the locus of enterocyte effacement (LEE). BipA positively regulated the espC and LEE gene clusters through transcriptional control of the LEE-encoded regulator, Ler. Additionally, it affected the pattern of proteolysis of intimin, a key LEE-encoded adhesin specified by the LEE. BipA control of the LEE operated independently of the previously characterized regulators Per, integration host factor and H-NS. In contrast, it negatively regulated the flagella-mediated motility of EPEC and in a Ler-independent manner. Our results indicate that the BipA GTPase functions high up in diverse regulatory cascades to co-ordinate the expression of key pathogenicity islands and other virulence-associated factors in E. coli.
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Affiliation(s)
- Andrew J Grant
- Division of Biochemistry and Molecular Biology, School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, UK
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Rowbury RJ. Introduction. Responses to weak acids, alkalinisation, biocides, UV irradiation, and toxic metal ions. Sci Prog 2003; 86:235-44. [PMID: 15508891 PMCID: PMC10361179 DOI: 10.3184/003685003783238617] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Abstract
Weak organic acids have been used for centuries to preserve foods, but only recently has the possible mechanism for bacterial growth inhibition been investigated. Although the lowering of internal pH was favored as the cause of growth inhibition, the emphasis has shifted to the anion and its specificity. There are a number of applications of weak organic acids to foods and in the food industry be they pre- or postharvest, However, there is concern that the ability of foodborne pathogens to adapt to these acids may allow longer survival in these commodities and also to better survive transit through the gastric acid barrier of the stomach. Genomic and proteomic approaches have been applied to the identification of genes and proteins that may allow prokaryotes to cope with organic acid stress. These technologies in combination with genetic approaches may provide better identification of genes essential for survival to organic acids. These acids may have other roles: they can induce phenotypic antibiotic resistance, and the high concentrations of these acids in the colon may signal a relationship to diet, colonic microflora, and human health.
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