1
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Daitch AK, Smith EL, Goley ED. OpgH is an essential regulator of Caulobacter morphology. mBio 2024; 15:e0144324. [PMID: 39145657 PMCID: PMC11389396 DOI: 10.1128/mbio.01443-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2024] [Accepted: 06/20/2024] [Indexed: 08/16/2024] Open
Abstract
Bacterial growth and division rely on intricate regulation of morphogenetic complexes to remodel the cell envelope without compromising envelope integrity. Significant progress has been made in recent years towards understanding the regulation of cell wall metabolic enzymes. However, other cell envelope components play a role in morphogenesis as well. A primary factor required to protect envelope integrity in low osmolarity environments is OpgH, the synthase of osmoregulated periplasmic glucans (OPGs). Here, we demonstrate that OpgH is essential in the α-proteobacterium Caulobacter crescentus. Unexpectedly, depletion of OpgH or attempted complementation with a catalytically dead OpgH variant results in striking asymmetric bulging and cell lysis. These shape defects are accompanied by reduced cell wall synthesis and mislocalization of morphogenetic complexes. Interestingly, overactivation of the CenKR two-component system that has been implicated in cell envelope stress homeostasis in α-proteobacteria phenocopies the morphogenetic defects associated with OpgH depletion. Each of these perturbations leads to an increase in the levels of the elongasome protein, MreB, and decreases in the levels of divisome proteins FtsZ and MipZ as well as OpgH, itself. Constitutive production of OpgH during CenKR overactivation prevents cell bulging, but cells still exhibit morphogenetic defects. We propose that OPG depletion activates CenKR, leading to changes in the expression of cell envelope-related genes, but that OPGs also exert CenKR-independent effects on morphogenesis. Our data establish a surprising function for an OpgH homolog in morphogenesis and reveal an essential role of OpgH in maintaining cell morphology in Caulobacter.IMPORTANCEBacteria must synthesize and fortify the cell envelope in a tightly regulated manner to orchestrate growth and adaptation. Osmoregulated periplasmic glucans (OPGs) are important, but poorly understood, constituents of Gram-negative cell envelopes that contribute to envelope integrity and protect against osmotic stress. Here, we determined that the OPG synthase OpgH plays a surprising, essential role in morphogenesis in Caulobacter crescentus. Loss of OpgH causes asymmetric cell bulging and lysis via misregulation of the localization and activity of morphogenetic complexes. Overactivation of the CenKR two-component system involved in envelope homeostasis phenocopies OpgH depletion, suggesting that depletion of OpgH activates CenKR. Because cell envelope integrity is critical for bacterial survival, understanding how OpgH activity contributes to morphogenesis and maintenance of envelope integrity could aid in the development of antibiotic therapies.
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Affiliation(s)
- Allison K Daitch
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Erika L Smith
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Erin D Goley
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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2
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Yin L, Wang X, Xu H, Yin B, Wang X, Zhang Y, Li X, Luo Y, Chen Z. Unrecognized risk of perfluorooctane sulfonate in promoting conjugative transfers of bacterial antibiotic resistance genes. Appl Environ Microbiol 2023; 89:e0053323. [PMID: 37565764 PMCID: PMC10537727 DOI: 10.1128/aem.00533-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 06/28/2023] [Indexed: 08/12/2023] Open
Abstract
Antibiotic resistance is a major global health crisis facing humanity, with horizontal gene transfer (HGT) as a principal dissemination mechanism in the natural and clinical environments. Perfluoroalkyl substances (PFASs) are emerging contaminants of global concern due to their high persistence in the environment and adverse effects on humans. However, it is unknown whether PFASs affect the HGT of bacterial antibiotic resistance. Using a genetically engineered Escherichia coli MG1655 as the donor of plasmid-encoded antibiotic resistance genes (ARGs), E. coli J53 and soil bacterial community as two different recipients, this study demonstrated that the conjugation frequency of ARGs between two E. coli strains was (1.45 ± 0.17) × 10-5 and perfluorooctane sulfonate (PFOS) at environmentally relevant concentrations (2-50 μg L-1) increased conjugation transfer between E. coli strains by up to 3.25-fold. Increases in reactive oxygen species production, cell membrane permeability, biofilm formation capacity, and cell contact in two E. coli strains were proposed as major promotion mechanisms from PFOS exposure. Weighted gene co-expression network analysis of transcriptome data identified a series of candidate genes whose expression changes could contribute to the increase in conjugation transfer induced by PFOS. Furthermore, PFOS also generally increased the ARG transfer into the studied soil bacterial community, although the uptake ability of different community members of the plasmid either increased or decreased upon PFOS exposure depending on specific bacterial taxa. Overall, this study reveals an unrecognized risk of PFOS in accelerating the dissemination of antibiotic resistance. IMPORTANCE Perfluoroalkyl substances (PFASs) are emerging contaminants of global concern due to their high persistence in the environment and adverse health effects. Although the influence of environmental pollutants on the spread of antibiotic resistance, one of the biggest threats to global health, has attracted increasing attention in recent years, it is unknown whether environmental residues of PFASs affect the dissemination of bacterial antibiotic resistance. Considering PFASs, often called "forever" compounds, have significantly higher environmental persistence than most emerging organic contaminants, exploring the effect of PFASs on the spread of antibiotic resistance is more environmentally relevant and has essential ecological and health significance. By systematically examining the influence of perfluorooctane sulfonate on the antibiotic resistance gene conjugative transfer, not only at the single-strain level but also at the community level, this study has uncovered an unrecognized risk of PFASs in promoting conjugative transfers of bacterial antibiotic resistance genes, which could be incorporated into the risk assessment framework of PFASs.
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Affiliation(s)
- Lichun Yin
- Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin, China
| | - Xiaolong Wang
- Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin, China
| | - Han Xu
- Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin, China
| | - Bo Yin
- Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin, China
| | - Xingshuo Wang
- Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin, China
| | - Yulin Zhang
- Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin, China
| | - Xinyao Li
- Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin, China
| | - Yi Luo
- Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin, China
| | - Zeyou Chen
- Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin, China
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3
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Motouchi S, Kobayashi K, Nakai H, Nakajima M. Identification of enzymatic functions of osmo-regulated periplasmic glucan biosynthesis proteins from Escherichia coli reveals a novel glycoside hydrolase family. Commun Biol 2023; 6:961. [PMID: 37735577 PMCID: PMC10514313 DOI: 10.1038/s42003-023-05336-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 09/08/2023] [Indexed: 09/23/2023] Open
Abstract
Most Gram-negative bacteria synthesize osmo-regulated periplasmic glucans (OPG) in the periplasm or extracellular space. Pathogenicity of many pathogens is lost by knocking out opgG, an OPG-related gene indispensable for OPG synthesis. However, the biochemical functions of OpgG and OpgD, a paralog of OpgG, have not been elucidated. In this study, structural and functional analyses of OpgG and OpgD from Escherichia coli revealed that these proteins are β-1,2-glucanases with remarkably different activity from each other, establishing a new glycoside hydrolase family, GH186. Furthermore, a reaction mechanism with an unprecedentedly long proton transfer pathway among glycoside hydrolase families is proposed for OpgD. The conformation of the region that forms the reaction pathway differs noticeably between OpgG and OpgD, which explains the observed low activity of OpgG. The findings enhance our understanding of OPG biosynthesis and provide insights into functional diversity for this novel enzyme family.
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Affiliation(s)
- Sei Motouchi
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda Chiba, 278-8510, Japan
| | - Kaito Kobayashi
- Artificial Intelligence Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 2-4-7 Aomi, Koto-ku, Tokyo, 135-0064, Japan
| | - Hiroyuki Nakai
- Faculty of Agriculture, Niigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata, 950-2181, Japan
| | - Masahiro Nakajima
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda Chiba, 278-8510, Japan.
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4
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Daitch AK, Goley ED. OpgH is an essential regulator of Caulobacter morphology. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.28.555136. [PMID: 37693447 PMCID: PMC10491104 DOI: 10.1101/2023.08.28.555136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Bacterial growth and division rely on intricate regulation of morphogenetic complexes to remodel the cell envelope without compromising envelope integrity. Significant progress has been made in recent years towards understanding the regulation of cell wall metabolic enzymes. However, other cell envelope components play a role in morphogenesis as well. Components required to maintain osmotic homeostasis are among these understudied envelope-associated enzymes that may contribute to cell morphology. A primary factor required to protect envelope integrity in low osmolarity environments is OpgH, the synthase of osmoregulated periplasmic glucans (OPGs). Here, we demonstrate that OpgH is essential in the α-proteobacterium Caulobacter crescentus. Unexpectedly, depletion of OpgH results in striking asymmetric bulging and cell lysis, accompanied by misregulation of cell wall insertion and mislocalization of morphogenetic complexes. The enzymatic activity of OpgH is required for normal cell morphology as production of an OpgH mutant that disrupts a conserved glycosyltransferase motif phenocopies the depletion. Our data establish a surprising function for an OpgH homolog in morphogenesis and reveal an essential role of OpgH in maintaining proper cell morphology during normal growth and division in Caulobacter.
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Affiliation(s)
- Allison K. Daitch
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, United States of America
- Current position: Johns Hopkins Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD, United States of America
| | - Erin D. Goley
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, United States of America
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5
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Gabale U, Peña Palomino PA, Kim H, Chen W, Ressl S. The essential inner membrane protein YejM is a metalloenzyme. Sci Rep 2020; 10:17794. [PMID: 33082366 PMCID: PMC7576196 DOI: 10.1038/s41598-020-73660-6] [Citation(s) in RCA: 12] [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: 01/23/2020] [Accepted: 09/18/2020] [Indexed: 12/27/2022] Open
Abstract
Recent recurrent outbreaks of Gram-negative bacteria show the critical need to target essential bacterial mechanisms to fight the increase of antibiotic resistance. Pathogenic Gram-negative bacteria have developed several strategies to protect themselves against the host immune response and antibiotics. One such strategy is to remodel the outer membrane where several genes are involved. yejM was discovered as an essential gene in E. coli and S. typhimurium that plays a critical role in their virulence by changing the outer membrane permeability. How the inner membrane protein YejM with its periplasmic domain changes membrane properties remains unknown. Despite overwhelming structural similarity between the periplasmic domains of two YejM homologues with hydrolases like arylsulfatases, no enzymatic activity has been previously reported for YejM. Our studies reveal an intact active site with bound metal ions in the structure of YejM periplasmic domain. Furthermore, we show that YejM has a phosphatase activity that is dependent on the presence of magnesium ions and is linked to its function of regulating outer membrane properties. Understanding the molecular mechanism by which YejM is involved in outer membrane remodeling will help to identify a new drug target in the fight against the increased antibiotic resistance.
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Affiliation(s)
- Uma Gabale
- Department of Molecular and Cellular Biochemistry, Indiana University Bloomington, 212 S Hawthrone Dr, Bloomington, IN, 47405, USA.
| | - Perla Arianna Peña Palomino
- Department of Molecular and Cellular Biochemistry, Indiana University Bloomington, 212 S Hawthrone Dr, Bloomington, IN, 47405, USA
| | - HyunAh Kim
- Department of Molecular and Cellular Biochemistry, Indiana University Bloomington, 212 S Hawthrone Dr, Bloomington, IN, 47405, USA
| | - Wenya Chen
- Department of Molecular and Cellular Biochemistry, Indiana University Bloomington, 212 S Hawthrone Dr, Bloomington, IN, 47405, USA
| | - Susanne Ressl
- Department of Molecular and Cellular Biochemistry, Indiana University Bloomington, 212 S Hawthrone Dr, Bloomington, IN, 47405, USA.
- Department of Neuroscience, The University of Texas At Austin, 100 E. 24th St., NHB 2.504, Austin, TX, 78712, USA.
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6
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Wenzel CQ, Mills DC, Dobruchowska JM, Vlach J, Nothaft H, Nation P, Azadi P, Melville SB, Carlson RW, Feldman MF, Szymanski CM. An atypical lipoteichoic acid from Clostridium perfringens elicits a broadly cross-reactive and protective immune response. J Biol Chem 2020; 295:9513-9530. [PMID: 32424044 DOI: 10.1074/jbc.ra119.009978] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 05/02/2020] [Indexed: 12/14/2022] Open
Abstract
Clostridium perfringens is a leading cause of food-poisoning and causes avian necrotic enteritis, posing a significant problem to both the poultry industry and human health. No effective vaccine against C. perfringens is currently available. Using an antiserum screen of mutants generated from a C. perfringens transposon-mutant library, here we identified an immunoreactive antigen that was lost in a putative glycosyltransferase mutant, suggesting that this antigen is likely a glycoconjugate. Following injection of formalin-fixed whole cells of C. perfringens HN13 (a laboratory strain) and JGS4143 (chicken isolate) intramuscularly into chickens, the HN13-derived antiserum was cross-reactive in immunoblots with all tested 32 field isolates, whereas only 5 of 32 isolates were recognized by JGS4143-derived antiserum. The immunoreactive antigens from both HN13 and JGS4143 were isolated, and structural analysis by MALDI-TOF-MS, GC-MS, and 2D NMR revealed that both were atypical lipoteichoic acids (LTAs) with poly-(β1→4)-ManNAc backbones substituted with phosphoethanolamine. However, although the ManNAc residues in JGS4143 LTA were phosphoethanolamine-modified, a few of these residues were instead modified with phosphoglycerol in the HN13 LTA. The JGS4143 LTA also had a terminal ribose and ManNAc instead of ManN in the core region, suggesting that these differences may contribute to the broadly cross-reactive response elicited by HN13. In a passive-protection chicken experiment, oral challenge with C. perfringens JGS4143 lead to 22% survival, whereas co-gavage with JGS4143 and α-HN13 antiserum resulted in 89% survival. This serum also induced bacterial killing in opsonophagocytosis assays, suggesting that HN13 LTA is an attractive target for future vaccine-development studies.
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Affiliation(s)
- Cory Q Wenzel
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.,VaxAlta Inc., Edmonton, Alberta, Canada.,Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
| | - Dominic C Mills
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | | | - Jiri Vlach
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA
| | - Harald Nothaft
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.,VaxAlta Inc., Edmonton, Alberta, Canada.,Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
| | - Patrick Nation
- Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada
| | - Parastoo Azadi
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA
| | - Stephen B Melville
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA
| | - Russell W Carlson
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA
| | - Mario F Feldman
- VaxAlta Inc., Edmonton, Alberta, Canada.,Department of Molecular Microbiology, Washington University of Medicine, St. Louis, Missouri, USA
| | - Christine M Szymanski
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada .,VaxAlta Inc., Edmonton, Alberta, Canada.,Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada.,Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA
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7
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Whole genome sequencing of four bacterial strains from South Shetland Trench revealing biosynthetic and environmental adaptation gene clusters. Mar Genomics 2020; 54:100782. [PMID: 32387528 DOI: 10.1016/j.margen.2020.100782] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2020] [Revised: 04/24/2020] [Accepted: 04/25/2020] [Indexed: 11/20/2022]
Abstract
Whole genome sequences of four bacterial strains Dietzia maris SST1, Pseudomonas zhaodongensis SST2, Pseudomonas sp. SST3 and Halomonas sulfidaeris SST4, recovered from the South Shetland Trench sediment in Antarctica were analyzed using Ion Torrent sequencing technology. The respective sizes of their genomes (3.88, 4.99, 5.60 and 4.25 Mb) and GC contents (70.0, 60.3, 59.9 and 53.8%) are in agreement with these values of other strains of the species. The bacterial strains displayed promising antimicrobial activity against a number of pathogenic bacterial and fungal species. Whole genomes have been assembled and biosynthetic gene clusters (BGCs) have been identified using the antibiotics and Secondary Metabolite Analysis Shell (antiSMASH) web platform. Comparative analysis of the genome sequences revealed that the strains host abundant BGCs encoding for terpenes, siderophores, arylpolyene, bacteriocins, and lassopeptides. Furthermore, the key stress-related genes were identified and their distribution provided an insight into how these isolates adapt to key marine environmental conditions. This comprehensive study is a contribution to understanding the nature of life on the deep-sea environments.
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8
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Sun L, Vella P, Schnell R, Polyakova A, Bourenkov G, Li F, Cimdins A, Schneider TR, Lindqvist Y, Galperin MY, Schneider G, Römling U. Structural and Functional Characterization of the BcsG Subunit of the Cellulose Synthase in Salmonella typhimurium. J Mol Biol 2018; 430:3170-3189. [PMID: 30017920 DOI: 10.1016/j.jmb.2018.07.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 07/02/2018] [Accepted: 07/05/2018] [Indexed: 11/17/2022]
Abstract
Many bacteria secrete cellulose, which forms the structural basis for bacterial multicellular aggregates, termed biofilms. The cellulose synthase complex of Salmonella typhimurium consists of the catalytic subunits BcsA and BcsB and several auxiliary subunits that are encoded by two divergently transcribed operons, bcsRQABZC and bcsEFG. Expression of the bcsEFG operon is required for full-scale cellulose production, but the functions of its products are not fully understood. This work aimed to characterize the BcsG subunit of the cellulose synthase, which consists of an N-terminal transmembrane fragment and a C-terminal domain in the periplasm. Deletion of the bcsG gene substantially decreased the total amount of BcsA and cellulose production. BcsA levels were partially restored by the expression of the transmembrane segment, whereas restoration of cellulose production required the presence of the C-terminal periplasmic domain and its characteristic metal-binding residues. The high-resolution crystal structure of the periplasmic domain characterized BcsG as a member of the alkaline phosphatase/sulfatase superfamily of metalloenzymes, containing a conserved Zn2+-binding site. Sequence and structural comparisons showed that BcsG belongs to a specific family within alkaline phosphatase-like enzymes, which includes bacterial Zn2+-dependent lipopolysaccharide phosphoethanolamine transferases such as MCR-1 (colistin resistance protein), EptA, and EptC and the Mn2+-dependent lipoteichoic acid synthase (phosphoglycerol transferase) LtaS. These enzymes use the phospholipids phosphatidylethanolamine and phosphatidylglycerol, respectively, as substrates. These data are consistent with the recently discovered phosphoethanolamine modification of cellulose by BcsG and show that its membrane-bound and periplasmic parts play distinct roles in the assembly of the functional cellulose synthase and cellulose production.
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Affiliation(s)
- Lei Sun
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Peter Vella
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Robert Schnell
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Anna Polyakova
- European Molecular Biology Laboratory, Hamburg Unit, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Gleb Bourenkov
- European Molecular Biology Laboratory, Hamburg Unit, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Fengyang Li
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Annika Cimdins
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Thomas R Schneider
- European Molecular Biology Laboratory, Hamburg Unit, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Ylva Lindqvist
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Michael Y Galperin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA.
| | - Gunter Schneider
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden.
| | - Ute Römling
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, S-171 77 Stockholm, Sweden.
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9
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Bhagwat AA, Young L, Smith AD, Bhagwat M. Transcriptomic Analysis of the Swarm Motility Phenotype of Salmonella enterica Serovar Typhimurium Mutant Defective in Periplasmic Glucan Synthesis. Curr Microbiol 2017; 74:1005-1014. [PMID: 28593349 DOI: 10.1007/s00284-017-1267-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 05/14/2017] [Indexed: 12/19/2022]
Abstract
Movement of food-borne pathogens on moist surfaces enables them to migrate towards more favorable niches and facilitate their survival for extended periods of time. Salmonella enterica serovar Typhimurium mutants defective in Osmoregulated periplasmic glucans (OPG) synthesis are unable to exhibit motility on moist surfaces (swarming); however, their mobility in liquid (swim motility) remains unaffected. In order to understand the role of OPG in swarm motility, transcriptomic analysis was performed using cells growing on a moist agar surface. In opgGH deletion mutant, lack of OPG significantly altered transcription of 1039 genes out of total 4712 genes (22%). Introduction of a plasmid-borne copy of opgGH into opgGH deletion mutant restored normal expression of all but 30 genes, indicating a wide-range influence of OPG on gene expression under swarm motility condition. Major pathways that were differentially expressed in opgGH mutants were motility, virulence and invasion, and genes related to the secondary messenger molecule, cyclic di-GMP. These observations provide insights and help explain the pleiotropic nature of OPG mutants such as sub-optimal virulence and competitive organ colonization in mice, biofilm formation, and sensitivity towards detergent stress.
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Affiliation(s)
- Arvind A Bhagwat
- Environmental, Microbial, & Food Safety Laboratory, Beltsville Agriculture Research Center, USDA-ARS (USDA/ARS/EMFSL), 10300 Baltimore Ave., B173, Rm. 204, BARC-E, Beltsville, MD, 20705, USA.
| | - Lynn Young
- National Institutes of Health Library, Division of Library Services, Office of Research Services, National Institute of Health, Building 10, Bethesda, MD, 20892, USA
| | - Allen D Smith
- Diet, Genomics and Immunology Laboratory, Beltsville Human Nutrition Research Center, USDA-ARS, Beltsville, MD, 20705, USA.
| | - Medha Bhagwat
- National Institutes of Health Library, Division of Library Services, Office of Research Services, National Institute of Health, Building 10, Bethesda, MD, 20892, USA
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10
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Abstract
Among all the systems developed by enterobacteria to face osmotic stress, only osmoregulated periplasmic glucans (OPGs) were found to be modulated during osmotic fluxes. First detected in 1973 by E.P. Kennedy's group in a study of phospholipid turnover in Escherichia coli, OPGs have been shown across alpha, beta, and gamma subdivisions of the proteobacteria. Discovery of OPG-like compounds in the epsilon subdivision strongly suggested that the presence of periplasmic glucans is essential for almost all proteobacteria. This article offers an overview of the different classes of OPGs. Then, the biosynthesis of OPGs and their regulation in E. coli and other species are discussed. Finally, the biological role of OPGs is developed. Beyond structural function, OPGs are involved in pathogenicity, in particular, by playing a role in signal transduction pathways. Recently, OPG synthesis proteins have been suggested to control cell division and growth rate.
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Affiliation(s)
- Sébastien Bontemps-Gallo
- Univ. Lille, CNRS, UMR 8576-UGSF-Unité de Glycobiologie Structurale et Fonctionnelle, F 59000 Lille, France
| | - Jean-Pierre Bohin
- Univ. Lille, CNRS, UMR 8576-UGSF-Unité de Glycobiologie Structurale et Fonctionnelle, F 59000 Lille, France
| | - Jean-Marie Lacroix
- Univ. Lille, CNRS, UMR 8576-UGSF-Unité de Glycobiologie Structurale et Fonctionnelle, F 59000 Lille, France
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11
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Walsh SI, Craney A, Romesberg FE. Not just an antibiotic target: Exploring the role of type I signal peptidase in bacterial virulence. Bioorg Med Chem 2016; 24:6370-6378. [PMID: 27769673 PMCID: PMC5279723 DOI: 10.1016/j.bmc.2016.09.048] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 09/17/2016] [Accepted: 09/19/2016] [Indexed: 01/23/2023]
Abstract
The looming antibiotic crisis has prompted the development of new strategies towards fighting infection. Traditional antibiotics target bacterial processes essential for viability, whereas proposed antivirulence approaches rely on the inhibition of factors that are required only for the initiation and propagation of infection within a host. Although antivirulence compounds have yet to prove their efficacy in the clinic, bacterial signal peptidase I (SPase) represents an attractive target in that SPase inhibitors exhibit broad-spectrum antibiotic activity, but even at sub-MIC doses also impair the secretion of essential virulence factors. The potential consequences of SPase inhibition on bacterial virulence have not been thoroughly examined, and are explored within this review. In addition, we review growing evidence that SPase has relevant biological functions outside of mediating secretion, and discuss how the inhibition of these functions may be clinically significant.
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Affiliation(s)
- Shawn I Walsh
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Arryn Craney
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Floyd E Romesberg
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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12
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The opgC gene is required for OPGs succinylation and is osmoregulated through RcsCDB and EnvZ/OmpR in the phytopathogen Dickeya dadantii. Sci Rep 2016; 6:19619. [PMID: 26790533 PMCID: PMC4726272 DOI: 10.1038/srep19619] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Accepted: 11/16/2015] [Indexed: 12/18/2022] Open
Abstract
Osmoregulated periplasmic glucans (OPGs) are a family of periplasmic oligosaccharides found in the envelope of most Proteobacteria. They are required for virulence of zoo- and phyto-pathogens. The glucose backbone of OPGs is substituted by various kinds of molecules depending on the species, O-succinyl residues being the most widely distributed. In our model, Dickeya dadantii, a phytopathogenic bacteria causing soft rot disease in a wide range of plant species, the backbone of OPGs is substituted by O-succinyl residues in media of high osmolarity and by O-acetyl residues whatever the osmolarity. The opgC gene encoding a transmembrane protein required for the succinylation of the OPGs in D. dadantii was found after an in silico search of a gene encoding a protein with the main characteristics recovered in the two previously characterized OpgC of E. coli and R. sphaeroides, i.e. 10 transmembrane segments and one acyl-transferase domain. Characterization of the opgC gene revealed that high osmolarity expression of the succinyl transferase is controlled by both the EnvZ-OmpR and RcsCDB phosphorelay systems. The loss of O-succinyl residue did not affect the virulence of D. dadantii, suggesting that only the glucose backbone of OPGs is required for virulence.
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13
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Abstract
Our view of bacteria is overwhelmingly shaped by their diminutive nature. The most ancient of organisms, their very presence was not appreciated until the 17th century with the invention of the microscope. Initially, viewed as "bags of enzymes," recent advances in imaging, molecular phylogeny, and, most recently, genomics have revealed incredible diversity within this previously invisible realm of life. Here, we review the impact of size on bacterial evolution, physiology, and morphogenesis.
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Affiliation(s)
- Petra Anne Levin
- Department of Biology, Washington University, St. Louis, Missouri 63130
| | - Esther R Angert
- Department of Microbiology, Cornell University, Ithaca, New York 14853
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14
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Dharne MS, Kannan P, Murphy C, Smith AD, Bhagwat AA. Swarm and swim motilities of Salmonella enterica serovar Typhimurium and role of osmoregulated periplasmic glucans. ACTA ACUST UNITED AC 2015. [DOI: 10.7243/2052-6180-3-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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15
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Percy MG, Gründling A. Lipoteichoic Acid Synthesis and Function in Gram-Positive Bacteria. Annu Rev Microbiol 2014; 68:81-100. [DOI: 10.1146/annurev-micro-091213-112949] [Citation(s) in RCA: 266] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Matthew G. Percy
- Section of Microbiology and MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, SW7 2AZ UK; ,
| | - Angelika Gründling
- Section of Microbiology and MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, SW7 2AZ UK; ,
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16
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Bontemps-Gallo S, Cogez V, Robbe-Masselot C, Quintard K, Dondeyne J, Madec E, Lacroix JM. Biosynthesis of osmoregulated periplasmic glucans in Escherichia coli: the phosphoethanolamine transferase is encoded by opgE. BIOMED RESEARCH INTERNATIONAL 2013; 2013:371429. [PMID: 24228245 PMCID: PMC3818809 DOI: 10.1155/2013/371429] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 08/30/2013] [Accepted: 09/02/2013] [Indexed: 11/18/2022]
Abstract
Osmoregulated periplasmic glucans (OPGs) are oligosaccharides found in the periplasm of many Gram-negative bacteria. Glucose is the sole constitutive sugar and this backbone may be substituted by various kinds of molecules depending on the species. In E. coli, OPG are substituted by phosphoglycerol and phosphoethanolamine derived from membrane phospholipids and by succinyl residues. In this study, we describe the isolation of the opgE gene encoding the phosphoethanolamine transferase by a screen previously used for the isolation of the opgB gene encoding the phosphoglycerol transferase. Both genes show structural and functional similarities without sequence similarity.
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Affiliation(s)
- Sébastien Bontemps-Gallo
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR CNRS 8576, IFR 147, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France
- Université Lille Nord de France, Lille, France
| | - Virginie Cogez
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR CNRS 8576, IFR 147, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France
- Université Lille Nord de France, Lille, France
| | - Catherine Robbe-Masselot
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR CNRS 8576, IFR 147, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France
- Université Lille Nord de France, Lille, France
| | - Kevin Quintard
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR CNRS 8576, IFR 147, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France
- Université Lille Nord de France, Lille, France
| | - Jacqueline Dondeyne
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR CNRS 8576, IFR 147, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France
- Université Lille Nord de France, Lille, France
| | - Edwige Madec
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR CNRS 8576, IFR 147, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France
- Université Lille Nord de France, Lille, France
| | - Jean-Marie Lacroix
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR CNRS 8576, IFR 147, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France
- Université Lille Nord de France, Lille, France
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17
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Metan G, Nedret Koc A, Ağkuş Ç, Kaynar LG, Alp E, Eser B. Can bacteraemia lead to false positive results in 1,3-beta-d-glucan test? Analysis of 83 bacteraemia episodes in high-risk patients for invasive fungal infections. Rev Iberoam Micol 2012; 29:169-71. [DOI: 10.1016/j.riam.2011.07.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2011] [Revised: 07/03/2011] [Accepted: 07/29/2011] [Indexed: 10/17/2022] Open
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18
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Abstract
Staphylococcus aureus is an important human pathogen whose virulence relies on the secretion of many different proteins. In general, the secretion of most proteins in S. aureus, as well as other bacteria, is dependent on the type I signal peptidase (SPase)-mediated cleavage of the N-terminal signal peptide that targets a protein to the general secretory pathway. The arylomycins are a class of natural product antibiotics that inhibit SPase, suggesting that they may be useful chemical biology tools for characterizing the secretome. While wild-type S. aureus (NCTC 8325) is naturally resistant to the arylomycins, sensitivity is conferred via a point mutation in its SPase. Here, we use a synthetic arylomycin along with a sensitized strain of S. aureus and multidimensional protein identification technology (MudPIT) mass spectrometry to identify 46 proteins whose extracellular accumulation requires SPase activity. Forty-four possess identifiable Sec-type signal peptides and thus are likely canonically secreted proteins, while four also appear to possess cell wall retention signals. We also identified the soluble C-terminal domains of two transmembrane proteins, lipoteichoic acid synthase, LtaS, and O-acyteltransferase, OatA, both of which appear to have noncanonical, internal SPase cleavage sites. Lastly, we identified three proteins, HtrA, PrsA, and SAOUHSC_01761, whose secretion is induced by arylomycin treatment. In addition to elucidating fundamental aspects of the physiology and pathology of S. aureus, the data suggest that an arylomycin-based therapeutic would reduce virulence while simultaneously eradicating an infection.
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19
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Proteolytic cleavage inactivates the Staphylococcus aureus lipoteichoic acid synthase. J Bacteriol 2011; 193:5279-91. [PMID: 21784926 DOI: 10.1128/jb.00369-11] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Lipoteichoic acid (LTA) is a crucial cell envelope component in Gram-positive bacteria. In Staphylococcus aureus, the polyglycerolphosphate LTA molecule is synthesized by LtaS, a membrane-embedded enzyme with five N-terminal transmembrane helices (5TM domain) that are connected via a linker region to the C-terminal extracellular enzymatic domain (eLtaS). The LtaS enzyme is processed during bacterial growth, and the eLtaS domain is released from the bacterial membrane. Here we provide experimental evidence that the proteolytic cleavage following residues 215Ala-Leu-Ala217 is performed by the essential S. aureus signal peptidase SpsB, as depletion of spsB results in reduced LtaS processing. In addition, the introduction of a proline residue at the +1 position with respect to the cleavage site, a substitution known to inhibit signal peptidase-dependent cleavage, abolished LtaS processing at this site. It was further shown that the 5TM domain is crucial for enzyme function. The observation that the construction of hybrid proteins between two functional LtaS-type enzymes resulted in the production of proteins unable to synthesize LTA suggests that specific interactions between the 5TM and eLtaS domains are required for function. No enzyme activity was detected upon expression of the 5TM and eLtaS domains as separate fragments, indicating that the two domains cannot assemble postsynthesis to form a functional enzyme. Taken together, our data suggest that only the full-length LtaS enzyme is active in the LTA synthesis pathway and that the proteolytic cleavage step is used as a mechanism to irreversibly inactivate the enzyme.
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20
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Abstract
Bacterial protein secretion is a highly orchestrated process that is essential for infection and virulence. Despite extensive efforts to predict or experimentally detect proteins that are secreted, the characterization of the bacterial secretome has remained challenging. A central event in protein secretion is the type I signal peptidase (SPase)-mediated cleavage of the N-terminal signal peptide that targets a protein for secretion via the general secretory pathway, and the arylomycins are a class of natural products that inhibit SPase, suggesting that they may be useful chemical biology tools for characterizing the secretome. Here, using an arylomycin derivative, along with two-dimensional gel electrophoresis and liquid chromatography-tandem mass spectrometry (LC-MS/MS), we identify 11 proteins whose secretion from stationary-phase Staphylococcus epidermidis is dependent on SPase activity, 9 of which are predicted to be translated with canonical N-terminal signal peptides. In addition, we find that the presence of extracellular domains of lipoteichoic acid synthase (LtaS) and the β-lactam response sensor BlaR1 in the medium is dependent on SPase activity, suggesting that they are cleaved at noncanonical sites within the protein. In all, the data define the proteins whose stationary-phase secretion depends on SPase and also suggest that the arylomycins should be valuable chemical biology tools for the study of protein secretion in a wide variety of different bacteria.
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21
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In vitro analysis of the Staphylococcus aureus lipoteichoic acid synthase enzyme using fluorescently labeled lipids. J Bacteriol 2010; 192:5341-9. [PMID: 20709894 DOI: 10.1128/jb.00453-10] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lipoteichoic acid (LTA) is an important cell wall component of Gram-positive bacteria. The key enzyme responsible for polyglycerolphosphate lipoteichoic acid synthesis in the Gram-positive pathogen Staphylococcus aureus is the membrane-embedded lipoteichoic acid synthase enzyme, LtaS. It is presumed that LtaS hydrolyzes the glycerolphosphate head group of the membrane lipid phosphatidylglycerol (PG) and catalyzes the formation of the polyglycerolphosphate LTA backbone chain. Here we describe an in vitro assay for this new class of enzyme using PG with a fluorescently labeled fatty acid chain (NBD-PG) as the substrate and the recombinant soluble C-terminal enzymatic domain of LtaS (eLtaS). Thin-layer chromatography and mass spectrometry analysis of the lipid reaction products revealed that eLtaS is sufficient to cleave the glycerolphosphate head group from NBD-PG, resulting in the formation of NBD-diacylglycerol. An excess of soluble glycerolphosphate could not compete with the hydrolysis of the fluorescently labeled PG lipid substrate, in contrast to the addition of unlabeled PG. This indicates that the enzyme recognizes and binds other parts of the lipid substrate, besides the glycerolphosphate head group. Furthermore, eLtaS activity was Mn(2+) ion dependent; Mg(2+) and Ca(2+) supported only weak enzyme activity. Addition of Zn(2+) or EDTA inhibited enzyme activity even in the presence of Mn(2+). The pH optimum of the enzyme was 6.5, characteristic for an enzyme that functions extracellularly. Lastly, we show that the in vitro assay can be used to study the enzyme activities of other members of the lipoteichoic acid synthase enzyme family.
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22
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Abstract
Periplasmic glucans (PGs) are general constituents in the periplasmic space of Proteobacteria. PGs from bacterial strains are found in larger amounts during growth on medium with low osmolarity and thus are often been specified as osmoregulated periplasmic glucans (OPGs). Furthermore, they appear to play crucial roles in pathogenesis and symbiosis. PGs have been classified into four families based on the structural features of their backbones, and they can be modified by a variety of non-sugar substituents. It has also recently been confirmed that novel PGs with various degrees of polymerization (DPs) and/or different substituents are produced under different growth conditions among Proteobacteria. In addition to their biological functions as regulators of low osmolarity, PGs have a variety of physico-chemical properties due to their inherent three-dimensional structures, hydrogen-bonding and complex-forming abilities. Thus, much attention has recently been focused on their physico-chemical applications. In this review, we provide an updated classification of PGs, as well as a description of the occurrences of novel PGs with substituents under various bacterial growth environments, the genes involved in PG biosynthesis and the various physico-chemical properties of PGs.
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Affiliation(s)
- Sanghoo Lee
- Department of Bioscience and Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
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23
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Liu L, Dharne M, Kannan P, Smith A, Meng J, Fan M, Boren TL, Ranallo RT, Bhagwat AA. Osmoregulated periplasmic glucans synthesis gene family of Shigella flexneri. Arch Microbiol 2010; 192:167-74. [PMID: 20062978 DOI: 10.1007/s00203-009-0538-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2009] [Revised: 11/20/2009] [Accepted: 12/17/2009] [Indexed: 11/29/2022]
Abstract
UNLABELLED Osmoregulated periplasmic glucans (OPGs) of food- and water-borne enteropathogen Shigella flexneri were characterized. OPGs were composed of 100% glucose with 2-linked glucose as the most abundant residue with terminal glucose, 2-linked and 2,6-linked glucose also present in high quantities. Most dominant backbone polymer chain length was seven glucose residues. Individual genes from the opg gene family comprising of a bicistronic operon opgGH, opgB, opgC and opgD were mutagenized to study their effect on OPGs synthesis, growth in hypo-osmotic media and ability to invade HeLa cells. Mutation in opgG and opgH abolished OPGs biosynthesis, and mutants experienced longer lag time to initiate growth in hypo-osmotic media. Longer lag times to initiate growth in hypo-osmotic media were also observed for opgC and opgD mutants but not for opgB mutant. All opg mutants were able to infect HeLa cells, and abolition of OPGs synthesis did not affect actin polymerization or plaque formation. Ability to synthesize OPGs was beneficial to bacteria in order to initiate growth under low osmolarity conditions, in vitro mammalian cell invasion assays, however, could not discriminate whether OPGs were required for basic aspect of Shigella virulence. ELECTRONIC SUPPLEMENTARY MATERIAL The online version of this article (doi:10.1007/s00203-009-0538-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Liu Liu
- College of Food Science and Technology, Northwest A&F University, 712100 Yangling, China
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24
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Costa CS, Pizarro RA, Antón DN. Influence of RpoS, cAMP-receptor protein, and ppGpp on expression of the opgGH operon and osmoregulated periplasmic glucan content of Salmonella enterica serovar Typhimurium. Can J Microbiol 2010; 55:1284-93. [PMID: 19940937 DOI: 10.1139/w09-086] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A transcriptional fusion (opgG1::MudJ) to the opgGH operon of Salmonella enterica serovar Typhimurium (S. Typhimurium) LT2, isolated by resistance to mecillinam, was used to study the influence of global regulators RpoS, ppGpp, and cAMP/cAMP-receptor protein (CRP) on expression of the opgGH operon and osmoregulated periplasmic glucan (OPG) content. Neither high growth medium osmolarity nor absence of ppGpp or CRP had important effects on opgG1::MudJ expression in exponential cultures. However, under the same conditions, OPG content was strongly decreased by high osmolarity or cAMP/CRP defectiveness, and reduced to a half by lack of ppGpp. In stationary cultures, high osmolarity as well as CRP loss caused significant descents in opgG1::MudJ expression that were compensated by inactivation of RpoS sigma factor. No effect of RpoS inactivation on OPG content was observed. It is concluded that opgGH expression in S. Typhimurium is only slightly affected by high osmolarity, but is inversely modulated by RpoS level. On the other hand, osmolarity and the cAMP/CRP global regulatory system appear to control OPG content, either directly or indirectly, mainly at the post-transcriptional level.
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Affiliation(s)
- Cristina S Costa
- Departamento de Radiobiología, Comisión Nacional de Energía Atómica, Avda. General Paz 1499, 1650 San Martín, Argentina
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25
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Structure-based mechanism of lipoteichoic acid synthesis by Staphylococcus aureus LtaS. Proc Natl Acad Sci U S A 2009; 106:1584-9. [PMID: 19168632 DOI: 10.1073/pnas.0809020106] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Staphylococcus aureus synthesizes polyglycerol-phosphate lipoteichoic acid (LTA) from phosphatidylglycerol. LtaS, a predicted membrane protein with 5 N-terminal transmembrane helices followed by a large extracellular part (eLtaS), is required for staphylococcal growth and LTA synthesis. Here, we report the first crystal structure of the eLtaS domain at 1.2-A resolution and show that it assumes a sulfatase-like fold with an alpha/beta core and a C-terminal part composed of 4 anti-parallel beta-strands and a long alpha-helix. Overlaying eLtaS with sulfatase structures identified active site residues, which were confirmed by alanine substitution mutagenesis and in vivo enzyme function assays. The cocrystal structure with glycerol-phosphate and the coordination of a Mn(2+) cation allowed us to propose a reaction mechanism, whereby the active site threonine of LtaS functions as nucleophile for phosphatidylglycerol hydrolysis and formation of a covalent threonine-glycerolphosphate intermediate. These results will aid in the development of LtaS-specific inhibitors for S. aureus and many other Gram-positive pathogens.
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