151
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Cao P, Wall D. The Fluidity of the Bacterial Outer Membrane Is Species Specific: Bacterial Lifestyles and the Emergence of a Fluid Outer Membrane. Bioessays 2020; 42:e1900246. [PMID: 32363627 PMCID: PMC7392792 DOI: 10.1002/bies.201900246] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 03/23/2020] [Indexed: 01/17/2023]
Abstract
The outer membrane (OM) is an essential barrier that guards Gram-negative bacteria from diverse environmental insults. Besides functioning as a chemical gatekeeper, the OM also contributes towards the strength and stiffness of cells and allows them to sustain mechanical stress. Largely influenced by studies of Escherichia coli, the OM is viewed as a rigid barrier where OM proteins and lipopolysaccharides display restricted mobility. Here the discussion is extended to other bacterial species, with a focus on Myxococcus xanthus. In contrast to the rigid OM paradigm, myxobacteria possess a relatively fluid OM. It is concluded that the fluidity of the OM varies across environmental species, which is likely linked to their evolution and adaptation to specific ecological niches. Importantly, a fluid OM can endow bacteria with distinct functions for cell-cell and cell-environment interactions.
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Affiliation(s)
| | - Daniel Wall
- Department of Molecular Biology, University of Wyoming, 1000 E University Avenue, Laramie, WY, 82071, USA
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152
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153
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Chen M, Song Y, Feng X, Tang K, Jiao N, Tian J, Zhang Y. Genomic Characteristics and Potential Metabolic Adaptations of Hadal Trench Roseobacter and Alteromonas Bacteria Based on Single-Cell Genomics Analyses. Front Microbiol 2020; 11:1739. [PMID: 32793171 PMCID: PMC7393951 DOI: 10.3389/fmicb.2020.01739] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Accepted: 07/03/2020] [Indexed: 11/30/2022] Open
Abstract
Heterotrophic bacteria such as those from the Roseobacter group and genus Alteromonas dominate the hadal zones of oceans; however, we know little about the genomic characteristics and potential metabolic adaptations of hadal trench-dwelling bacteria. Here, we report multiple single amplified genomes (SAGs) belonging to Roseobacter and Alteromonas, recovered from the hadal zone of the Mariana Trench. While phylogenetic analyses show that these hadal SAGs cluster with their surface relatives, an analysis of genomic recruitment indicates that they have higher relative abundances in the hadal zone of the Mariana Trench. Comparative genomic analyses between the hadal SAGs and reference genomes of closely related shallow-water relatives indicate that genes involved in the mobilome (prophages and transposons) are overrepresented among the unique genes of the hadal Roseobacter and Alteromonas SAGs; the functional proteins encoded by this category of genes also shows higher amino acid sequence variation than those encoded by other gene sets within the Roseobacter SAGs. We also found that genes involved in cell wall/membrane/envelope biogenesis, transcriptional regulation, and metal transport may be important for the adaptation of hadal Roseobacter and Alteromonas lineages. These results imply that the modification of cell surface-related proteins and transporters is the major direction of genomic evolution in Roseobacter and Alteromonas bacteria adapting to the hadal environment, and that prophages and transposons may be the key factors driving this process.
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Affiliation(s)
- Mingming Chen
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Xiamen University, Xiamen, China
| | - Yu Song
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Xiamen University, Xiamen, China
| | - Xiaoyuan Feng
- School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Kai Tang
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Xiamen University, Xiamen, China
| | - Nianzhi Jiao
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Xiamen University, Xiamen, China
| | - Jiwei Tian
- Physical Oceanography Laboratory, Ocean University of China, Qingdao, China
| | - Yao Zhang
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Xiamen University, Xiamen, China
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154
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Horne JE, Brockwell DJ, Radford SE. Role of the lipid bilayer in outer membrane protein folding in Gram-negative bacteria. J Biol Chem 2020; 295:10340-10367. [PMID: 32499369 PMCID: PMC7383365 DOI: 10.1074/jbc.rev120.011473] [Citation(s) in RCA: 77] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 06/03/2020] [Indexed: 01/09/2023] Open
Abstract
β-Barrel outer membrane proteins (OMPs) represent the major proteinaceous component of the outer membrane (OM) of Gram-negative bacteria. These proteins perform key roles in cell structure and morphology, nutrient acquisition, colonization and invasion, and protection against external toxic threats such as antibiotics. To become functional, OMPs must fold and insert into a crowded and asymmetric OM that lacks much freely accessible lipid. This feat is accomplished in the absence of an external energy source and is thought to be driven by the high thermodynamic stability of folded OMPs in the OM. With such a stable fold, the challenge that bacteria face in assembling OMPs into the OM is how to overcome the initial energy barrier of membrane insertion. In this review, we highlight the roles of the lipid environment and the OM in modulating the OMP-folding landscape and discuss the factors that guide folding in vitro and in vivo We particularly focus on the composition, architecture, and physical properties of the OM and how an understanding of the folding properties of OMPs in vitro can help explain the challenges they encounter during folding in vivo Current models of OMP biogenesis in the cellular environment are still in flux, but the stakes for improving the accuracy of these models are high. OMP folding is an essential process in all Gram-negative bacteria, and considering the looming crisis of widespread microbial drug resistance it is an attractive target. To bring down this vital OMP-supported barrier to antibiotics, we must first understand how bacterial cells build it.
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Affiliation(s)
- Jim E Horne
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - David J Brockwell
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
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155
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Chiang Y, Wei ST, Wang P, Wu P, Yu C. Microbial degradation of steroid sex hormones: implications for environmental and ecological studies. Microb Biotechnol 2020; 13:926-949. [PMID: 31668018 PMCID: PMC7264893 DOI: 10.1111/1751-7915.13504] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 10/09/2019] [Accepted: 10/09/2019] [Indexed: 12/13/2022] Open
Abstract
Steroid hormones modulate development, reproduction and communication in eukaryotes. The widespread occurrence and persistence of steroid hormones have attracted public attention due to their endocrine-disrupting effects on both wildlife and human beings. Bacteria are responsible for mineralizing steroids from the biosphere. Aerobic degradation of steroid hormones relies on O2 as a co-substrate of oxygenases to activate and to cleave the recalcitrant steroidal core ring. To date, two oxygen-dependent degradation pathways - the 9,10-seco pathway for androgens and the 4,5-seco pathways for oestrogens - have been characterized. Under anaerobic conditions, denitrifying bacteria adopt the 2,3-seco pathway to degrade different steroid structures. Recent meta-omics revealed that microorganisms able to degrade steroids are highly diverse and ubiquitous in different ecosystems. This review also summarizes culture-independent approaches using the characteristic metabolites and catabolic genes to monitor steroid biodegradation in various ecosystems.
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Affiliation(s)
- Yin‐Ru Chiang
- Biodiversity Research CenterAcademia SinicaTaipei115Taiwan
| | | | - Po‐Hsiang Wang
- Biodiversity Research CenterAcademia SinicaTaipei115Taiwan
- Present address:
Earth‐Life Science InstituteTokyo Institute of TechnologyTokyoJapan
| | - Pei‐Hsun Wu
- Graduate Institute of Environmental EngineeringNational Taiwan UniversityTaipei106Taiwan
| | - Chang‐Ping Yu
- Graduate Institute of Environmental EngineeringNational Taiwan UniversityTaipei106Taiwan
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156
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Kolich LR, Chang YT, Coudray N, Giacometti SI, MacRae MR, Isom GL, Teran EM, Bhabha G, Ekiert DC. Structure of MlaFB uncovers novel mechanisms of ABC transporter regulation. eLife 2020; 9:e60030. [PMID: 32602838 PMCID: PMC7367683 DOI: 10.7554/elife.60030] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 06/24/2020] [Indexed: 12/12/2022] Open
Abstract
ABC transporters facilitate the movement of diverse molecules across cellular membranes, but how their activity is regulated post-translationally is not well understood. Here we report the crystal structure of MlaFB from E. coli, the cytoplasmic portion of the larger MlaFEDB ABC transporter complex, which drives phospholipid trafficking across the bacterial envelope to maintain outer membrane integrity. MlaB, a STAS domain protein, binds the ABC nucleotide binding domain, MlaF, and is required for its stability. Our structure also implicates a unique C-terminal tail of MlaF in self-dimerization. Both the C-terminal tail of MlaF and the interaction with MlaB are required for the proper assembly of the MlaFEDB complex and its function in cells. This work leads to a new model for how an important bacterial lipid transporter may be regulated by small proteins, and raises the possibility that similar regulatory mechanisms may exist more broadly across the ABC transporter family.
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Affiliation(s)
- Ljuvica R Kolich
- Department of Cell Biology, New York University School of MedicineNew YorkUnited States
| | - Ya-Ting Chang
- Department of Cell Biology, New York University School of MedicineNew YorkUnited States
| | - Nicolas Coudray
- Department of Cell Biology, New York University School of MedicineNew YorkUnited States
- Applied Bioinformatics Laboratory, New York University School of MedicineNew YorkUnited States
| | - Sabrina I Giacometti
- Department of Cell Biology, New York University School of MedicineNew YorkUnited States
| | - Mark R MacRae
- Department of Cell Biology, New York University School of MedicineNew YorkUnited States
| | - Georgia L Isom
- Department of Cell Biology, New York University School of MedicineNew YorkUnited States
| | - Evelyn M Teran
- Department of Cell Biology, New York University School of MedicineNew YorkUnited States
| | - Gira Bhabha
- Department of Cell Biology, New York University School of MedicineNew YorkUnited States
| | - Damian C Ekiert
- Department of Cell Biology, New York University School of MedicineNew YorkUnited States
- Department of Microbiology, New York University School of MedicineNew YorkUnited States
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157
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Elliott AG, Huang JX, Neve S, Zuegg J, Edwards IA, Cain AK, Boinett CJ, Barquist L, Lundberg CV, Steen J, Butler MS, Mobli M, Porter KM, Blaskovich MAT, Lociuro S, Strandh M, Cooper MA. An amphipathic peptide with antibiotic activity against multidrug-resistant Gram-negative bacteria. Nat Commun 2020; 11:3184. [PMID: 32576824 PMCID: PMC7311426 DOI: 10.1038/s41467-020-16950-x] [Citation(s) in RCA: 88] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 06/03/2020] [Indexed: 11/09/2022] Open
Abstract
Peptide antibiotics are an abundant and synthetically tractable source of molecular diversity, but they are often cationic and can be cytotoxic, nephrotoxic and/or ototoxic, which has limited their clinical development. Here we report structure-guided optimization of an amphipathic peptide, arenicin-3, originally isolated from the marine lugworm Arenicola marina. The peptide induces bacterial membrane permeability and ATP release, with serial passaging resulting in a mutation in mlaC, a phospholipid transport gene. Structure-based design led to AA139, an antibiotic with broad-spectrum in vitro activity against multidrug-resistant and extensively drug-resistant bacteria, including ESBL, carbapenem- and colistin-resistant clinical isolates. The antibiotic induces a 3–4 log reduction in bacterial burden in mouse models of peritonitis, pneumonia and urinary tract infection. Cytotoxicity and haemolysis of the progenitor peptide is ameliorated with AA139, and the ‘no observable adverse effect level’ (NOAEL) dose in mice is ~10-fold greater than the dose generally required for efficacy in the infection models. Peptide antibiotics often display a very narrow therapeutic index. Here, the authors present an optimized peptide antibiotic with broad-spectrum in vitro activities, in vivo efficacy in multiple disease models against multidrug-resistant Gram-negative infections, and reduced toxicity.
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Affiliation(s)
- Alysha G Elliott
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Queensland, QLD, 4072, Australia
| | - Johnny X Huang
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Queensland, QLD, 4072, Australia.,School of Life Science and Technology, Weifang Medical University, Weifang, 261053, China
| | - Søren Neve
- Orphazyme, Ole Maaloesvej 3, 2200, Copenhagen, Denmark
| | - Johannes Zuegg
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Queensland, QLD, 4072, Australia
| | - Ingrid A Edwards
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Queensland, QLD, 4072, Australia
| | - Amy K Cain
- Wellcome Sanger Institute, Hinxton, UK.,Department of Molecular Sciences, Macquarie University, NSW, 2109, Australia
| | | | - Lars Barquist
- Helmholtz Institute for RNA-based Infection Research (HIRI), Würzburg, Germany.,Faculty of Medicine, University of Würzburg, Würzburg, Germany
| | | | - Jason Steen
- School of Chemistry and Molecular Biosciences, The University of Queensland, Queensland, Qld, Australia
| | - Mark S Butler
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Queensland, QLD, 4072, Australia
| | - Mehdi Mobli
- Centre for Advanced Imaging, The University of Queensland, Queensland, Qld, Australia
| | - Kaela M Porter
- Adenium Biotech ApS, Ole Maaloesvej 3, 2200, Copenhagen, Denmark
| | - Mark A T Blaskovich
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Queensland, QLD, 4072, Australia
| | - Sergio Lociuro
- BioVersys AG, Hochbergerstrasse 60C, Technology Park, 4057, Basel, Switzerland
| | - Magnus Strandh
- Adenium Biotech ApS, Ole Maaloesvej 3, 2200, Copenhagen, Denmark
| | - Matthew A Cooper
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Queensland, QLD, 4072, Australia. .,Trinity College Dublin, Dublin, Ireland.
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158
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Outer Membrane Lipid Secretion and the Innate Immune Response to Gram-Negative Bacteria. Infect Immun 2020; 88:IAI.00920-19. [PMID: 32253250 DOI: 10.1128/iai.00920-19] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The outer membrane (OM) of Gram-negative bacteria is an asymmetric lipid bilayer that consists of inner leaflet phospholipids and outer leaflet lipopolysaccharides (LPS). The asymmetric character and unique biochemistry of LPS molecules contribute to the OM's ability to function as a molecular permeability barrier that protects the bacterium against hazards in the environment. Assembly and regulation of the OM have been extensively studied for understanding mechanisms of antibiotic resistance and bacterial defense against host immunity; however, there is little knowledge on how Gram-negative bacteria release their OMs into their environment to manipulate their hosts. Discoveries in bacterial lipid trafficking, OM lipid homeostasis, and host recognition of microbial patterns have shed new light on how microbes secrete OM vesicles (OMVs) to influence inflammation, cell death, and disease pathogenesis. Pathogens release OMVs that contain phospholipids, like cardiolipins, and components of LPS molecules, like lipid A endotoxins. These multiacylated lipid amphiphiles are molecular patterns that are differentially detected by host receptors like the Toll-like receptor 4/myeloid differentiation factor 2 complex (TLR4/MD-2), mouse caspase-11, and human caspases 4 and 5. We discuss how lipid ligands on OMVs engage these pattern recognition receptors on the membranes and in the cytosol of mammalian cells. We then detail how bacteria regulate OM lipid asymmetry, negative membrane curvature, and the phospholipid-to-LPS ratio to control OMV formation. The goal is to highlight intersections between OM lipid regulation and host immunity and to provide working models for how bacterial lipids influence vesicle formation.
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159
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Nilsson I, Lee SY, Sawyer WS, Baxter Rath CM, Lapointe G, Six DA. Metabolic phospholipid labeling of intact bacteria enables a fluorescence assay that detects compromised outer membranes. J Lipid Res 2020; 61:870-883. [PMID: 32156718 PMCID: PMC7269758 DOI: 10.1194/jlr.ra120000654] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 03/03/2020] [Indexed: 01/09/2023] Open
Abstract
Gram-negative bacteria possess an asymmetric outer membrane (OM) composed primarily of lipopolysaccharides (LPSs) on the outer leaflet and phospholipids (PLs) on the inner leaflet. The loss of this asymmetry due to mutations in the LPS biosynthesis or transport pathways causes the externalization of PLs to the outer leaflet of the OM and leads to OM permeability defects. Here, we used metabolic labeling to detect a compromised OM in intact bacteria. Phosphatidylcholine synthase expression in Escherichia coli allowed for the incorporation of exogenous propargylcholine into phosphatidyl(propargyl)choline and exogenous 1-azidoethyl-choline (AECho) into phosphatidyl(azidoethyl)choline (AEPC), as confirmed by LC/MS analyses. A fluorescent copper-free click reagent poorly labeled AEPC in intact wild-type cells but readily labeled AEPC from lysed cells. Fluorescence microscopy and flow cytometry analyses confirmed the absence of significant AEPC labeling from intact wild-type E. coli strains and revealed significant AEPC labeling in an E. coli LPS transport mutant (lptD4213) and an LPS biosynthesis mutant (E. coli lpxC101). Our results suggest that metabolic PL labeling with AECho is a promising tool for detecting a compromised bacterial OM, revealing aberrant PL externalization, and identifying or characterizing novel cell-active inhibitors of LPS biosynthesis or transport.
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Affiliation(s)
- Inga Nilsson
- Infectious Diseases Area Novartis Institutes for BioMedical Research, Emeryville, CA; Global Discovery Chemistry Novartis Institutes for BioMedical Research, Emeryville, CA
| | - Sheng Y Lee
- Infectious Diseases Area Novartis Institutes for BioMedical Research, Emeryville, CA
| | - William S Sawyer
- Infectious Diseases Area Novartis Institutes for BioMedical Research, Emeryville, CA
| | | | - Guillaume Lapointe
- Global Discovery Chemistry Novartis Institutes for BioMedical Research, Emeryville, CA
| | - David A Six
- Infectious Diseases Area Novartis Institutes for BioMedical Research, Emeryville, CA. mailto:
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160
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Li M, Aye SM, Ahmed MU, Han ML, Li C, Song J, Boyce JD, Powell DR, Azad MAK, Velkov T, Zhu Y, Li J. Pan-transcriptomic analysis identified common differentially expressed genes of Acinetobacter baumannii in response to polymyxin treatments. Mol Omics 2020; 16:327-338. [PMID: 32469363 DOI: 10.1039/d0mo00015a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Multidrug-resistant Acinetobacter baumannii is a top-priority Gram-negative pathogen and polymyxins are a last-line therapeutic option. Previous systems pharmacological studies examining polymyxin killing and resistance usually focused on individual strains, and the derived knowledge could be limited by strain-specific genomic context. In this study, we examined the gene expression of five A. baumannii strains (34654, 1207552, 1428368, 1457504 and ATCC 19606) to determine the common differentially expressed genes in response to polymyxin treatments. A pan-genome containing 6061 genes was identified for 89 A. baumannii genomes from RefSeq database which included the five strains examined in this study; 2822 of the 6061 genes constituted the core genome. After 2 mg L-1 or 0.75 × MIC polymyxin treatments for 15 min, 41 genes were commonly up-regulated, including those involved in membrane biogenesis and homeostasis, lipoprotein and phospholipid trafficking, efflux pump and poly-N-acetylglucosamine biosynthesis; six genes were commonly down-regulated, three of which were related to fatty acid biosynthesis. Additionally, comparison of the gene expression at 15 and 60 min in ATCC 19606 revealed that polymyxin treatment resulted in a rapid change in amino acid metabolism at 15 min and perturbations on envelope biogenesis at both time points. This is the first pan-transcriptomic study for polymyxin-treated A. baumannii and our results identified that the remodelled outer membrane, up-regulated efflux pumps and down-regulated fatty acid biosynthesis might be essential for early responses to polymyxins in A. baumannii. Our findings provide important mechanistic insights into bacterial responses to polymyxin killing and may facilitate the optimisation of polymyxin therapy against this problematic 'superbug'.
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Affiliation(s)
- Mengyao Li
- Biomedicine Discovery Institute, Infection & Immunity Program and Department of Microbiology, Monash University, 19 Innovation Walk, Melbourne 3800, Australia.
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161
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Pitt ME, Cao MD, Butler MS, Ramu S, Ganesamoorthy D, Blaskovich MAT, Coin LJM, Cooper MA. Octapeptin C4 and polymyxin resistance occur via distinct pathways in an epidemic XDR Klebsiella pneumoniae ST258 isolate. J Antimicrob Chemother 2020; 74:582-593. [PMID: 30445429 DOI: 10.1093/jac/dky458] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 10/09/2018] [Accepted: 10/09/2018] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Polymyxin B and E (colistin) have been pivotal in the treatment of XDR Gram-negative bacterial infections; however, resistance has emerged. A structurally related lipopeptide, octapeptin C4, has shown significant potency against XDR bacteria, including polymyxin-resistant strains, but its mode of action remains undefined. OBJECTIVES We sought to compare and contrast the acquisition of resistance in an XDR Klebsiella pneumoniae (ST258) clinical isolate in vitro with all three lipopeptides to potentially unveil variations in their mode of action. METHODS The isolate was exposed to increasing concentrations of polymyxins and octapeptin C4 over 20 days. Day 20 strains underwent WGS, complementation assays, antimicrobial susceptibility testing and lipid A analysis. RESULTS Twenty days of exposure to the polymyxins resulted in a 1000-fold increase in the MIC, whereas for octapeptin C4 a 4-fold increase was observed. There was no cross-resistance observed between the polymyxin- and octapeptin-resistant strains. Sequencing of polymyxin-resistant isolates revealed mutations in previously known resistance-associated genes, including crrB, mgrB, pmrB, phoPQ and yciM, along with novel mutations in qseC. Octapeptin C4-resistant isolates had mutations in mlaDF and pqiB, genes related to phospholipid transport. These genetic variations were reflected in distinct phenotypic changes to lipid A. Polymyxin-resistant isolates increased 4-amino-4-deoxyarabinose fortification of lipid A phosphate groups, whereas the lipid A of octapeptin C4-resistant strains harboured a higher abundance of hydroxymyristate and palmitoylate. CONCLUSIONS Octapeptin C4 has a distinct mode of action compared with the polymyxins, highlighting its potential as a future therapeutic agent to combat the increasing threat of XDR bacteria.
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Affiliation(s)
- Miranda E Pitt
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Minh Duc Cao
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Mark S Butler
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Soumya Ramu
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Devika Ganesamoorthy
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Mark A T Blaskovich
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Lachlan J M Coin
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Matthew A Cooper
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
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162
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Batista JH, Leal FC, Fukuda TTH, Alcoforado Diniz J, Almeida F, Pupo MT, da Silva Neto JF. Interplay between two quorum sensing-regulated pathways, violacein biosynthesis and VacJ/Yrb, dictates outer membrane vesicle biogenesis in Chromobacterium violaceum. Environ Microbiol 2020; 22:2432-2442. [PMID: 32329144 DOI: 10.1111/1462-2920.15033] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 04/09/2020] [Accepted: 04/20/2020] [Indexed: 02/06/2023]
Abstract
Outer membrane vesicles (OMVs) are lipid nanoparticles released by Gram-negative bacteria, which play multiple roles in bacterial physiology and adaptation to diverse environments. In this work, we demonstrate that OMVs released by the environmental pathogen Chromobacterium violaceum deliver the antimicrobial compound violacein to competitor bacteria, mediating its toxicity in vivo at a long distance. OMVs purified by ultracentrifugation from the wild-type strain, but not from a violacein-abrogated mutant ΔvioABCDE, contained violacein and inhibited several Gram-positive bacteria. Competition tests using co-culture and transwell assays indicated that the C. violaceum wild-type strain killed Staphylococcus aureus better than the ΔvioABCDE mutant strain. We found that C. violaceum achieves growth phase-dependent OMV release by the concerted expression of two quorum sensing (QS)-regulated pathways, namely violacein biosynthesis and VacJ/Yrb system. Although both pathways were activated at high cell density in a QS-dependent manner, the effect on vesiculation was the opposite. While the ΔvioABCDE mutant produced twofold fewer vesicles than the wild-type strain, indicating that violacein induces OMV biogenesis for its own delivery, the ΔvacJ and ΔyrbE mutants were hypervesiculating strains. Our findings uncovered QS-regulated pathways involved in OMV biogenesis used by C. violaceum to package violacein into OMVs for interbacterial competition.
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Affiliation(s)
- Juliana H Batista
- Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Fernanda C Leal
- Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Taise T H Fukuda
- Departamento de Ciências Farmacêuticas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Juliana Alcoforado Diniz
- Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Fausto Almeida
- Departamento de Bioquímica e Imunologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Mônica T Pupo
- Departamento de Ciências Farmacêuticas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - José F da Silva Neto
- Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
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163
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Verma S, Prescott RA, Ingano L, Nickerson KP, Hill E, Faherty CS, Fasano A, Senger S, Cherayil BJ. The YrbE phospholipid transporter of Salmonella enterica serovar Typhi regulates the expression of flagellin and influences motility, adhesion and induction of epithelial inflammatory responses. Gut Microbes 2020; 11:526-538. [PMID: 31829769 PMCID: PMC7527071 DOI: 10.1080/19490976.2019.1697593] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
serovar Typhi is the etiologic agent of typhoid fever, a major public health problem in the developing world. Moving toward and adhering to the intestinal epithelium represents key initial steps of infection by S. Typhi. We examined the role of the S. Typhi yrbE gene, which encodes an inner membrane phospholipid transporter, in these interactions with epithelial cells. Disruption of yrbE resulted in elevated expression of flagellin and a hypermotile phenotype. It also significantly reduced the ability of S. Typhi to adhere to the HeLa epithelial cell line and to polarized primary epithelial cells derived from human ileal organoids. Interestingly, the yrbE-deficient strain of S. Typhi induced higher production of interleukin-8 from the primary human ileal epithelial cell monolayers compared to the wild-type bacteria. Deletion of the flagellin gene (fliC) in the yrbE-deficient S. Typhi inhibited motility and attenuated interleukin-8 production, but it did not correct the defect in adhesion. We also disrupted yrbE in S. Typhimurium. In contrast to the results in S. Typhi, the deficiency of yrbE in S. Typhimurium had no significant effect on flagellin expression, motility or adhesion to HeLa cells. Correspondingly, the lack of yrbE also had no effect on association with the intestine or the severity of intestinal inflammation in the mouse model of S. Typhimurium infection. Thus, our results point to an important and serovar-specific role played by yrbE in the early stages of intestinal infection by S. Typhi.
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Affiliation(s)
- Smriti Verma
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA,Department of Pediatrics, Harvard Medical School, Boston, MA, USA
| | - Rachel A. Prescott
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Laura Ingano
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Kourtney P. Nickerson
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA,Department of Pediatrics, Harvard Medical School, Boston, MA, USA
| | - Emily Hill
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Christina S. Faherty
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA,Department of Pediatrics, Harvard Medical School, Boston, MA, USA
| | - Alessio Fasano
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA,Department of Pediatrics, Harvard Medical School, Boston, MA, USA
| | - Stefania Senger
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA,Department of Pediatrics, Harvard Medical School, Boston, MA, USA
| | - Bobby J. Cherayil
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA,Department of Pediatrics, Harvard Medical School, Boston, MA, USA,CONTACT Bobby J. Cherayil Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, MA, USA
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164
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Bai L, Parkin LA, Zhang H, Shum R, Previti ML, Seeliger JC. Dimethylaminophenyl Hydrazides as Inhibitors of the Lipid Transport Protein LprG in Mycobacteria. ACS Infect Dis 2020; 6:637-648. [PMID: 32053347 PMCID: PMC7436943 DOI: 10.1021/acsinfecdis.9b00497] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Assembly of the bacterial cell wall requires not only the biosynthesis of cell wall components but also the transport of these metabolites to the cell exterior for assembly into polymers and membranes required for bacterial viability and virulence. LprG is a cell wall protein that is required for the virulence of Mycobacterium tuberculosis and is associated with lipid transport to the outer lipid layer or mycomembrane. Motivated by available cocrystal structures of LprG with lipids, we searched for potential inhibitors of LprG by performing a computational docking screen of ∼250 000 commercially available small molecules. We identified several structurally related dimethylaminophenyl hydrazides that bind to LprG with moderate micromolar affinity and inhibit mycobacterial growth in a LprG-dependent manner. We found that mutation of F123 within the binding cavity of LprG conferred resistance to one of the most potent compounds. These findings provide evidence that the large hydrophobic substrate-binding pocket of LprG can be realistically and specifically targeted by small-molecule inhibitors.
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Affiliation(s)
- Lu Bai
- Department of Chemistry, Stony Brook University, 100
Nicolls Road, Stony Brook, NY 11794
| | - Lia A. Parkin
- Department of Microbiology and Immunology, Stony Brook
University, 100 Nicolls Road, Stony Brook, NY 11794
| | - Hong Zhang
- Department of Chemistry, Stony Brook University, 100
Nicolls Road, Stony Brook, NY 11794
| | - Rebecca Shum
- Department of Biochemistry and Cell Biology, Stony Brook
University, 100 Nicolls Road, Stony Brook, NY 11794
| | - Mary L. Previti
- Department of Pharmacological Sciences, Stony Brook
University, 100 Nicolls Road, Stony Brook, NY 11794
| | - Jessica C. Seeliger
- Department of Pharmacological Sciences, Stony Brook
University, 100 Nicolls Road, Stony Brook, NY 11794
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165
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Yakhnina AA, Bernhardt TG. The Tol-Pal system is required for peptidoglycan-cleaving enzymes to complete bacterial cell division. Proc Natl Acad Sci U S A 2020; 117:6777-6783. [PMID: 32152098 PMCID: PMC7104345 DOI: 10.1073/pnas.1919267117] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Tol-Pal is a multiprotein system present in the envelope of Gram-negative bacteria. Inactivation of this widely conserved machinery compromises the outer membrane (OM) layer of these organisms, resulting in hypersensitivity to many antibiotics. Mutants in the tol-pal locus fail to complete division and form cell chains. This phenotype along with the localization of Tol-Pal components to the cytokinetic ring in Escherichia coli has led to the proposal that the primary function of the system is to promote OM constriction during division. Accordingly, a poorly constricted OM is believed to link the cell chains formed upon Tol-Pal inactivation. However, we show here that cell chains of E. coli tol-pal mutants are connected by an incompletely processed peptidoglycan (PG) layer. Genetic suppressors of this defect were isolated and found to overproduce OM lipoproteins capable of cleaving the glycan strands of PG. Among the factors promoting cell separation in mutant cells was a protein of previously unknown function (YddW), which we have identified as a divisome-localized glycosyl hydrolase that cleaves peptide-free PG glycans. Overall, our results indicate that the cell chaining defect of Tol-Pal mutants cannot simply be interpreted as a defect in OM constriction. Rather, the complex also appears to be required for the activity of several OM-localized enzymes with cell wall remodeling activity. Thus, the Tol-Pal system may play a more general role in coordinating OM invagination with PG remodeling at the division site than previously appreciated.
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Affiliation(s)
| | - Thomas G Bernhardt
- Department of Microbiology, Harvard Medical School, Boston, MA 02115;
- Howard Hughes Medical Institute, Boston, MA 02115
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166
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Chu J, Liu J, Hoover TR. Phylogenetic Distribution, Ultrastructure, and Function of Bacterial Flagellar Sheaths. Biomolecules 2020; 10:biom10030363. [PMID: 32120823 PMCID: PMC7175336 DOI: 10.3390/biom10030363] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 02/25/2020] [Accepted: 02/26/2020] [Indexed: 02/06/2023] Open
Abstract
A number of Gram-negative bacteria have a membrane surrounding their flagella, referred to as the flagellar sheath, which is continuous with the outer membrane. The flagellar sheath was initially described in Vibrio metschnikovii in the early 1950s as an extension of the outer cell wall layer that completely surrounded the flagellar filament. Subsequent studies identified other bacteria that possess flagellar sheaths, most of which are restricted to a few genera of the phylum Proteobacteria. Biochemical analysis of the flagellar sheaths from a few bacterial species revealed the presence of lipopolysaccharide, phospholipids, and outer membrane proteins in the sheath. Some proteins localize preferentially to the flagellar sheath, indicating mechanisms exist for protein partitioning to the sheath. Recent cryo-electron tomography studies have yielded high resolution images of the flagellar sheath and other structures closely associated with the sheath, which has generated insights and new hypotheses for how the flagellar sheath is synthesized. Various functions have been proposed for the flagellar sheath, including preventing disassociation of the flagellin subunits in the presence of gastric acid, avoiding activation of the host innate immune response by flagellin, activating the host immune response, adherence to host cells, and protecting the bacterium from bacteriophages.
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Affiliation(s)
- Joshua Chu
- Department of Microbiology, Cornell University, Ithaca, NY 14853, USA;
| | - Jun Liu
- Microbial Sciences Institute, Department of Microbial Pathogenesis, Yale University, West Haven, CT 06516, USA;
| | - Timothy R. Hoover
- Department of Microbiology, University of Georgia, Athens, GA 30602, USA
- Correspondence: ; Tel.: +1-706-542-2675
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167
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A Screen for Antibiotic Resistance Determinants Reveals a Fitness Cost of the Flagellum in Pseudomonas aeruginosa. J Bacteriol 2020; 202:JB.00682-19. [PMID: 31871033 DOI: 10.1128/jb.00682-19] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 12/18/2019] [Indexed: 01/09/2023] Open
Abstract
The intrinsic resistance of Pseudomonas aeruginosa to many antibiotics limits treatment options for pseudomonal infections. P. aeruginosa's outer membrane is highly impermeable and decreases antibiotic entry into the cell. We used an unbiased high-throughput approach to examine mechanisms underlying outer membrane-mediated antibiotic exclusion. Insertion sequencing (INSeq) identified genes that altered fitness in the presence of linezolid, rifampin, and vancomycin, antibiotics to which P. aeruginosa is intrinsically resistant. We reasoned that resistance to at least one of these antibiotics would depend on outer membrane barrier function, as previously demonstrated in Escherichia coli and Vibrio cholerae This approach demonstrated a critical role of the outer membrane barrier in vancomycin fitness, while efflux pumps were primary contributors to fitness in the presence of linezolid and rifampin. Disruption of flagellar assembly or function was sufficient to confer a fitness advantage to bacteria exposed to vancomycin. These findings clearly show that loss of flagellar function alone can confer a fitness advantage in the presence of an antibiotic.IMPORTANCE The cell envelopes of Gram-negative bacteria render them intrinsically resistant to many classes of antibiotics. We used insertion sequencing to identify genes whose disruption altered the fitness of a highly antibiotic-resistant pathogen, Pseudomonas aeruginosa, in the presence of antibiotics usually excluded by the cell envelope. This screen identified gene products involved in outer membrane biogenesis and homeostasis, respiration, and efflux as important contributors to fitness. An unanticipated fitness cost of flagellar assembly and function in the presence of the glycopeptide antibiotic vancomycin was further characterized. These findings have clinical relevance for individuals with cystic fibrosis who are infected with P. aeruginosa and undergo treatment with vancomycin for a concurrent Staphylococcus aureus infection.
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168
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169
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Jugder BE, Watnick PI. Vibrio cholerae Sheds Its Coat to Make Itself Comfortable in the Gut. Cell Host Microbe 2020; 27:161-163. [PMID: 32053783 DOI: 10.1016/j.chom.2020.01.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Invertebrates molt, furry mammals shed, and human skin exfoliates. In this issue of Cell Host & Microbe, Zingl et al. describe a virulence mechanism in which the bacterial pathogen Vibrio cholerae jettisons outer membrane proteins and lipids in vesicles as it enters the mammalian intestine.
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Affiliation(s)
- Bat-Erdene Jugder
- Division of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Paula I Watnick
- Division of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA.
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170
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Zingl FG, Kohl P, Cakar F, Leitner DR, Mitterer F, Bonnington KE, Rechberger GN, Kuehn MJ, Guan Z, Reidl J, Schild S. Outer Membrane Vesiculation Facilitates Surface Exchange and In Vivo Adaptation of Vibrio cholerae. Cell Host Microbe 2019; 27:225-237.e8. [PMID: 31901519 DOI: 10.1016/j.chom.2019.12.002] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 10/25/2019] [Accepted: 12/05/2019] [Indexed: 10/25/2022]
Abstract
Gram-negative bacteria release outer membrane vesicles into the external milieu to deliver effector molecules that alter the host and facilitate virulence. Vesicle formation is driven by phospholipid accumulation in the outer membrane and regulated by the phospholipid transporter VacJ/Yrb. We use the facultative human pathogen Vibrio cholerae to show that VacJ/Yrb is silenced early during mammalian infection, which stimulates vesiculation that expedites bacterial surface exchange and adaptation to the host environment. Hypervesiculating strains rapidly alter their bacterial membrane composition and exhibit enhanced intestinal colonization fitness. This adaptation is exemplified by faster accumulation of glycine-modified lipopolysaccharide (LPS) and depletion of outer membrane porin OmpT, which confers resistance to host-derived antimicrobial peptides and bile, respectively. The competitive advantage of hypervesiculation is lost upon pre-adaptation to bile and antimicrobial peptides, indicating the importance of these adaptive processes. Thus, bacteria use outer membrane vesiculation to exchange cell surface components, thereby increasing survival during mammalian infection.
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Affiliation(s)
- Franz G Zingl
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Paul Kohl
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Fatih Cakar
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Deborah R Leitner
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Fabian Mitterer
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | | | - Gerald N Rechberger
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria; Center for Explorative Lipidomics, BioTechMed Graz, 8010 Graz, Austria
| | - Meta J Kuehn
- Duke University Medical Center, Durham, NC 27710, USA
| | - Ziqiang Guan
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
| | - Joachim Reidl
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria; BioTechMed Graz, 8010 Graz, Austria
| | - Stefan Schild
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria; BioTechMed Graz, 8010 Graz, Austria.
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171
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Liu C, Ma J, Wang J, Wang H, Zhang L. Cryo-EM Structure of a Bacterial Lipid Transporter YebT. J Mol Biol 2019; 432:1008-1019. [PMID: 31870848 DOI: 10.1016/j.jmb.2019.12.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 12/02/2019] [Accepted: 12/03/2019] [Indexed: 12/13/2022]
Abstract
The outer membrane (OM) of Gram-negative bacteria is asymmetric, with lipopolysaccharides (LPSs) on the outer surface and phospholipids (PLs) on the inner surface. This unique organization of OM makes Gram-negative bacteria resistant to many toxic chemicals. How this asymmetric distribution of lipids is maintained has been studied for decades with previous reports of an Mla (Maintenance of OM Lipid Asymmetry) system to be involved. Furthermore, the OM of Gram-negative bacteria is about 20 nm away from inner membrane (IM) where the lipids are synthesized. Therefore, how nascent lipids travel across the periplasmic space and arrive at the inner surface of OM is another interesting question. YebT is a homologue of MlaD in the Mla pathway, but its role in lipid distribution of the OM and IM is largely unknown. Here we report the first high-resolution (~3.0 Å) cryo-EM structure of full-length E. coli YebT in a substrate-bound state. Our structure with details of lipid interaction indicates that YebT is a lipid transporter spanning between IM and OM. We also demonstrate the symmetry mismatch in YebT and the existence of many other conformations of YebT revealing the intrinsic dynamics of this lipid channel. And a brief discussion on possible mechanisms of lipid transport is also included.
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Affiliation(s)
- Chuan Liu
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua University, Beijing, China; Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, China; School of Life Sciences, Tsinghua University, Beijing, China; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Jinying Ma
- School of Life Sciences, Tsinghua University, Beijing, China
| | - Jia Wang
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua University, Beijing, China; Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, China; School of Life Sciences, Tsinghua University, Beijing, China; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Hongwei Wang
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua University, Beijing, China; Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, China; School of Life Sciences, Tsinghua University, Beijing, China; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Li Zhang
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua University, Beijing, China; Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, China; School of Life Sciences, Tsinghua University, Beijing, China; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China.
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172
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Kintses B, Jangir PK, Fekete G, Számel M, Méhi O, Spohn R, Daruka L, Martins A, Hosseinnia A, Gagarinova A, Kim S, Phanse S, Csörgő B, Györkei Á, Ari E, Lázár V, Nagy I, Babu M, Pál C, Papp B. Chemical-genetic profiling reveals limited cross-resistance between antimicrobial peptides with different modes of action. Nat Commun 2019; 10:5731. [PMID: 31844052 PMCID: PMC6915728 DOI: 10.1038/s41467-019-13618-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 11/14/2019] [Indexed: 11/09/2022] Open
Abstract
Antimicrobial peptides (AMPs) are key effectors of the innate immune system and promising therapeutic agents. Yet, knowledge on how to design AMPs with minimal cross-resistance to human host-defense peptides remains limited. Here, we systematically assess the resistance determinants of Escherichia coli against 15 different AMPs using chemical-genetics and compare to the cross-resistance spectra of laboratory-evolved AMP-resistant strains. Although generalizations about AMP resistance are common in the literature, we find that AMPs with different physicochemical properties and cellular targets vary considerably in their resistance determinants. As a consequence, cross-resistance is prevalent only between AMPs with similar modes of action. Finally, our screen reveals several genes that shape susceptibility to membrane- and intracellular-targeting AMPs in an antagonistic manner. We anticipate that chemical-genetic approaches could inform future efforts to minimize cross-resistance between therapeutic and human host AMPs.
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Affiliation(s)
- Bálint Kintses
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre, Szeged, Hungary.
- HCEMM-BRC Translational Microbiology Lab, Szeged, Hungary.
- Department of Biochemistry and Molecular Biology, University of Szeged, Szeged, Hungary.
| | - Pramod K Jangir
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre, Szeged, Hungary
- Doctoral School of Biology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Gergely Fekete
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre, Szeged, Hungary
- HCEMM-BRC Metabolic Systems Biology Lab, Szeged, Hungary
| | - Mónika Számel
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre, Szeged, Hungary
- Doctoral School of Biology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Orsolya Méhi
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre, Szeged, Hungary
| | - Réka Spohn
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre, Szeged, Hungary
| | - Lejla Daruka
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre, Szeged, Hungary
- Doctoral School of Biology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Ana Martins
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre, Szeged, Hungary
| | - Ali Hosseinnia
- Department of Biochemistry, University of Regina, Regina, Saskatchewan, Canada
| | - Alla Gagarinova
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Sunyoung Kim
- Department of Biochemistry, University of Regina, Regina, Saskatchewan, Canada
| | - Sadhna Phanse
- Department of Biochemistry, University of Regina, Regina, Saskatchewan, Canada
| | - Bálint Csörgő
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre, Szeged, Hungary
- Department of Microbiology and Immunology, University of California, San Francisco, USA
| | - Ádám Györkei
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre, Szeged, Hungary
- HCEMM-BRC Metabolic Systems Biology Lab, Szeged, Hungary
| | - Eszter Ari
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre, Szeged, Hungary
- HCEMM-BRC Metabolic Systems Biology Lab, Szeged, Hungary
- Department of Genetics, Eötvös Loránd University, Budapest, Hungary
| | - Viktória Lázár
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre, Szeged, Hungary
- Faculty of Biology, Technion - Israel Institute of Technology, Haifa, Israel
| | - István Nagy
- Sequencing Platform, Institute of Biochemistry, Biological Research Centre, Szeged, Hungary
| | - Mohan Babu
- Department of Biochemistry, University of Regina, Regina, Saskatchewan, Canada
| | - Csaba Pál
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre, Szeged, Hungary.
| | - Balázs Papp
- Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre, Szeged, Hungary.
- HCEMM-BRC Metabolic Systems Biology Lab, Szeged, Hungary.
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173
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Abstract
Lipids are distributed in a highly heterogeneous fashion in different cellular membranes. Only a minority of lipids achieve their final intracellular distribution through transport by vesicles. Instead, the bulk of lipid traffic is mediated by a large group of lipid transfer proteins (LTPs), which move small numbers of lipids at a time using hydrophobic cavities that stabilize lipid molecules outside membranes. Although the first LTPs were discovered almost 50 years ago, most progress in understanding these proteins has been made in the past few years, leading to considerable temporal and spatial refinement of our understanding of the function of these lipid transporters. The number of known LTPs has increased, with exciting discoveries of their multimeric assembly. Structural studies of LTPs have progressed from static crystal structures to dynamic structural approaches that show how conformational changes contribute to lipid handling at a sub-millisecond timescale. A major development has been the finding that many intracellular LTPs localize to two organelles at the same time, forming a shuttle, bridge or tube that links donor and acceptor compartments. The understanding of how different lipids achieve their final destination at the molecular level allows a better explanation of the range of defects that occur in diseases associated with lipid transport and distribution, opening up the possibility of developing therapies that specifically target lipid transfer.
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174
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Porins and small-molecule translocation across the outer membrane of Gram-negative bacteria. Nat Rev Microbiol 2019; 18:164-176. [DOI: 10.1038/s41579-019-0294-2] [Citation(s) in RCA: 135] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/16/2019] [Indexed: 02/07/2023]
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175
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Robust Suppression of Lipopolysaccharide Deficiency in Acinetobacter baumannii by Growth in Minimal Medium. J Bacteriol 2019; 201:JB.00420-19. [PMID: 31451545 DOI: 10.1128/jb.00420-19] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 08/19/2019] [Indexed: 12/12/2022] Open
Abstract
Lipopolysaccharide (LPS) is normally considered to be essential for viability in Gram-negative bacteria but can be removed in Acinetobacter baumannii Mutant cells lacking this component of the outer membrane show growth and morphological defects. Here, we report that growth rates equivalent to the wild type can be achieved simply by propagation in minimal medium. The loss of LPS requires that cells rely on phospholipids for both leaflets of the outer membrane. We show that growth rate in the absence of LPS is not limited by nutrient availability but by the rate of outer membrane biogenesis. We hypothesize that because cells grow more slowly, outer membrane synthesis ceases to be rate limiting in minimal medium.IMPORTANCE Gram-negative bacteria are defined by their asymmetric outer membrane that consists of phospholipids on the inner leaflet and lipopolysaccharide (LPS) in the outer leaflet. LPS is essential in all but a few Gram-negative species; the reason for this differential essentiality is not well understood. One species that can survive without LPS, Acinetobacter baumannii, shows characteristic growth and morphology phenotypes. We show that these phenotypes can be suppressed under conditions of slow growth and describe how LPS loss is connected to the growth defects. In addition to better defining the challenges A. baumannii cells face in the absence of LPS, we provide a new hypothesis that may explain the species-dependent conditional essentiality.
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176
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Sperandeo P, Polissi A, De Fabiani E. Fat Matters for Bugs: How Lipids and Lipid Modifications Make the Difference in Bacterial Life. EUR J LIPID SCI TECH 2019. [DOI: 10.1002/ejlt.201900204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Paola Sperandeo
- Dipartimento di Scienze Farmacologiche e BiomolecolariUniversità degli Studi di MilanoVia Balzaretti 920133MilanoItaly
| | - Alessandra Polissi
- Dipartimento di Scienze Farmacologiche e BiomolecolariUniversità degli Studi di MilanoVia Balzaretti 920133MilanoItaly
| | - Emma De Fabiani
- Dipartimento di Scienze Farmacologiche e BiomolecolariUniversità degli Studi di MilanoVia Balzaretti 920133MilanoItaly
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177
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Seib KL, Haag AF, Oriente F, Fantappiè L, Borghi S, Semchenko EA, Schulz BL, Ferlicca F, Taddei AR, Giuliani MM, Pizza M, Delany I. The meningococcal vaccine antigen GNA2091 is an analogue of YraP and plays key roles in outer membrane stability and virulence. FASEB J 2019; 33:12324-12335. [DOI: 10.1096/fj.201900669r] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Kate L. Seib
- Institute for GlycomicsGriffith UniversityGold CoastQueenslandAustralia
| | | | | | | | | | | | - Benjamin L. Schulz
- School of Chemistry and Molecular BiosciencesThe University of QueenslandBrisbaneQueenslandAustralia
| | | | - Anna Rita Taddei
- Interdepartmental Centre of Electron Microscopy (CIME)Tuscia UniversityTusciaItaly
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Screen for fitness and virulence factors of Francisella sp. strain W12-1067 using amoebae. Int J Med Microbiol 2019; 309:151341. [PMID: 31451389 DOI: 10.1016/j.ijmm.2019.151341] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 07/17/2019] [Accepted: 08/18/2019] [Indexed: 11/21/2022] Open
Abstract
Francisella tularensis is the causative agent of the human disease referred to as tularemia. Other Francisella species are known but less is understood about their virulence factors. The role of environmental amoebae in the life-cycle of Francisella is still under discussion. Francisella sp. strain W12-1067 (F-W12) is an environmental Francisella isolate recently identified in Germany which is negative for the Francisella pathogenicity island, but exhibits a putative alternative type VI secretion system. Putative virulence factors have been identified in silico in the genome of F-W12. In this work, we established a "scatter screen", used earlier for pathogenic Legionella, to verify experimentally and identify candidate fitness factors using a transposon mutant bank of F-W12 and Acanthamoeba lenticulata as host organism. In these experiments, we identified 79 scatter clones (amoeba sensitive), which were further analyzed by an infection assay identifying 9 known virulence factors, but also candidate fitness factors of F-W12 not yet described as fitness factors in Francisella. The majority of the identified genes encoded proteins involved in the synthesis or maintenance of the cell envelope (LPS, outer membrane, capsule) or in the metabolism (glycolysis, gluconeogenesis, pentose phosphate pathway). Further 13C-flux analysis of the Tn5 glucokinase mutant strain revealed that the identified gene indeed encodes the sole active glucokinase in F-W12. In conclusion, candidate fitness factors of the new Francisella species F-W12 were identified using the scatter screen method which might also be usable for other Francisella species.
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179
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Intermembrane transport: Glycerophospholipid homeostasis of the Gram-negative cell envelope. Proc Natl Acad Sci U S A 2019; 116:17147-17155. [PMID: 31420510 PMCID: PMC6717313 DOI: 10.1073/pnas.1902026116] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
This perspective addresses recent advances in lipid transport across the Gram-negative inner and outer membranes. While we include a summary of previously existing literature regarding this topic, we focus on the maintenance of lipid asymmetry (Mla) pathway. Discovered in 2009 by the Silhavy group [J. C. Malinverni, T. J. Silhavy, Proc. Natl. Acad. Sci. U.S.A. 106, 8009–8014 (2009)], Mla has become increasingly appreciated for its role in bacterial cell envelope physiology. Through the work of many, we have gained an increasingly mechanistic understanding of the function of Mla via genetic, biochemical, and structural methods. Despite this, there is a degree of controversy surrounding the directionality in which Mla transports lipids. While the initial discovery and subsequent studies have posited that it mediated retrograde lipid transport (removing glycerophospholipids from the outer membrane and returning them to the inner membrane), others have asserted the opposite. This Perspective aims to lay out the evidence in an unbiased, yet critical, manner for Mla-mediated transport in addition to postulation of mechanisms for anterograde lipid transport from the inner to outer membranes.
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180
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Abstract
The outer membrane (OM) of Gram-negative bacteria exhibits unique lipid asymmetry, with lipopolysaccharides (LPS) residing in the outer leaflet and phospholipids (PLs) in the inner leaflet. This asymmetric bilayer protects the bacterium against intrusion of many toxic substances, including antibiotics and detergents, yet allows acquisition of nutrients necessary for growth. To build the OM and ensure its proper function, the cell produces OM constituents in the cytoplasm or inner membrane and transports these components across the aqueous periplasmic space separating the two membranes. Of note, the processes by which the most basic membrane building blocks, i.e. PLs, are shuttled across the cell envelope remain elusive. This review highlights our current understanding (or lack thereof) of bacterial PL trafficking, with a focus on recent developments in the field. We adopt a mechanistic approach and draw parallels and comparisons with well-characterized systems, particularly OM lipoprotein and LPS transport, to illustrate key challenges in intermembrane lipid trafficking. Pathways that transport PLs across the bacterial cell envelope are fundamental to OM biogenesis and homeostasis and are potential molecular targets that could be exploited for antibiotic development.
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Affiliation(s)
- Rahul Shrivastava
- Department of Chemistry, National University of Singapore, Singapore 117543, Singapore
| | - Shu-Sin Chng
- Department of Chemistry, National University of Singapore, Singapore 117543, Singapore
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181
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Abstract
Genes necessary for the survival or reproduction of a cell are an attractive class of antibiotic targets. Studying essential genes by classical genetics, however, is inherently problematic because it is impossible to knock them out. Here, we screened a set of predicted essential genes for growth inhibition using CRISPR-interference (CRISPRi) knockdown in the human pathogen Vibrio cholerae We demonstrate that CRISPRi knockdown of 37 predicted essential genes inhibits V. cholerae viability, thus validating the products of these genes as potential drug target candidates. V. cholerae was particularly vulnerable to lethal inhibition of the system for lipoprotein transport (Lol), a central hub for directing lipoproteins from the inner to the outer membrane (OM), with many of these lipoproteins coordinating their own essential processes. Lol depletion makes cells prone to plasmolysis and elaborate membrane reorganization, during which the periplasm extrudes into a mega outer membrane vesicle or "MOMV" encased by OM which dynamically emerges specifically at plasmolysis sites. Our work identifies the Lol system as an ideal drug target, whose inhibition could deplete gram-negative bacteria of numerous proteins that reside in the periplasm.
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182
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Singh AK, Mishra H, Firdaus Z, Yadav S, Aditi P, Nandy N, Sharma K, Bose P, Pandey AK, Chauhan BS, Neogi K, Vikram K, Srivastava A, Kar AG, Prakash P. MoS 2-Modified Curcumin Nanostructures: The Novel Theranostic Hybrid Having Potent Antibacterial and Antibiofilm Activities against Multidrug-Resistant Hypervirulent Klebsiella pneumoniae. Chem Res Toxicol 2019; 32:1599-1618. [PMID: 31315397 DOI: 10.1021/acs.chemrestox.9b00135] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The recent emergence of hypervirulent clinical variants of Klebsiella pneumoniae (hvKP) causing community-acquired, invasive, metastatic, life-threatening infections of lungs, pleura, prostate, bones, joints, kidneys, spleen, muscles, soft-tissues, skin, eyes, central nervous system (CNS) including extrahepatic abscesses, and primary bacteremia even in healthy individuals has posed stern challenges before the existing treatment modalities. There is therefore an urgent need to look for specific and effective therapeutic alternatives against the said bacterial infection or recurrence. A new type of MoS2-modified curcumin nanostructure has been developed and evaluated as a potential alternative for the treatment of multidrug-resistant isolates. The curcumin quantum particles have been fabricated with MoS2 via a seed-mediated hydrothermal method, and the resulting MoS2-modified curcumin nanostructures (MQCs) have been subsequently tested for their antibacterial and antibiofilm properties against hypervirulent multidrug-resistant Klebsiella pneumoniae isolates. In the present study, we found MQCs inhibiting the bacterial growth at a minimal concentration of 0.0156 μg/mL, while complete inhibition of bacterial growth was evinced at concentration 0.125 μg/mL. Besides, we also investigated their biocompatibility both in vitro and in vivo. MQCs were found to be nontoxic to the SiHa cells at a dose as high as 1024 μg/mL on the basis of the tested adhesion, spreading of the cells, and also on the various serological, biochemical, and histological investigations of the vital organs and blood of the Charles Foster Rat. These results suggest that MQCs have potent antimicrobial activities against hvKP and other drug resistant isolates and therefore may be used as broad spectrum antibacterial and antibiofilm agents.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | - Kunwar Vikram
- Department of Physics , Indian Institutes of Sciences , Bangalore 560012 , India.,Graphic Era University , Dehradun 248002 , India
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183
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Lin Y, Zheng L, Bogdanov M. Measurement of Lysophospholipid Transport Across the Membrane Using Escherichia coli Spheroplasts. Methods Mol Biol 2019; 1949:165-180. [PMID: 30790256 DOI: 10.1007/978-1-4939-9136-5_13] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
In the inner membrane of Gram-negative bacteria lysophospholipid transporter (LplT) and the bifunctional acyl-acyl carrier protein (ACP) synthetase/2-acylglycerolphosphoethanolamine acyltransferase (Aas) form a glycerophospholipid remodeling system, which is capable of facilitating rapid retrograde translocation of lyso forms of phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin across the cytoplasmic membrane. This coupled remodeling enzyme tandem provides an effective method for the measurement of substrate specificity of the lipid regeneration and lysophospholipid transport per se across the membrane. This chapter describes two distinct but complementary methods for the measurement of lysophospholipid transport across membrane using Escherichia coli spheroplasts.
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Affiliation(s)
- Yibin Lin
- Division of Infectious Diseases, Department of Pediatrics, Center for Antimicrobial Resistance and Microbial Genomics, University of Texas Health Science Center at Houston McGovern Medical School, Houston, TX, USA.
| | - Lei Zheng
- Department of Biochemistry and Molecular Biology, Center for Membrane Biology, University of Texas Health Science Center at Houston McGovern Medical School, Houston, TX, USA
| | - Mikhail Bogdanov
- Department of Biochemistry and Molecular Biology, University of Texas Health Science Center at Houston McGovern Medical School, Houston, TX, USA.,Department of Biochemistry and Biotechnology, Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russian Federation
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184
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Cao P, Wall D. Direct visualization of a molecular handshake that governs kin recognition and tissue formation in myxobacteria. Nat Commun 2019; 10:3073. [PMID: 31300643 PMCID: PMC6626042 DOI: 10.1038/s41467-019-11108-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 06/17/2019] [Indexed: 12/13/2022] Open
Abstract
Many organisms regulate their social life through kin recognition, but the underlying mechanisms are poorly understood. Here, we use a social bacterium, Myxococcus xanthus, to investigate kin recognition at the molecular level. By direct visualization of a cell surface receptor, TraA, we show how these myxobacteria identify kin and transition towards multicellularity. TraA is fluid on the cell surface, and homotypic interactions between TraA from juxtaposed cells trigger the receptors to coalesce, representing a ‘molecular handshake’. Polymorphisms within TraA govern social recognition such that receptors cluster only between individuals bearing compatible alleles. TraA clusters, which resemble eukaryotic gap junctions, direct the robust exchange of cellular goods that allows heterogeneous populations to transition towards homeostasis. This work provides a conceptual framework for how microbes use a fluid outer membrane receptor to recognize and assemble kin cells into a cooperative multicellular community that resembles a tissue. Many organisms, including the bacterium Myxococcus xanthus, regulate their social life through kin recognition. Here, Cao and Wall show that these bacteria use a polymorphic and fluid cell-surface receptor to recognize and assemble kin cells into a cooperative multicellular community that resembles a tissue.
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Affiliation(s)
- Pengbo Cao
- Department of Molecular Biology, University of Wyoming, 1000 E University Avenue, Laramie, WY, 82071, USA.,School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Daniel Wall
- Department of Molecular Biology, University of Wyoming, 1000 E University Avenue, Laramie, WY, 82071, USA.
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185
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Hughes GW, Hall SCL, Laxton CS, Sridhar P, Mahadi AH, Hatton C, Piggot TJ, Wotherspoon PJ, Leney AC, Ward DG, Jamshad M, Spana V, Cadby IT, Harding C, Isom GL, Bryant JA, Parr RJ, Yakub Y, Jeeves M, Huber D, Henderson IR, Clifton LA, Lovering AL, Knowles TJ. Evidence for phospholipid export from the bacterial inner membrane by the Mla ABC transport system. Nat Microbiol 2019; 4:1692-1705. [DOI: 10.1038/s41564-019-0481-y] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Accepted: 05/03/2019] [Indexed: 12/24/2022]
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186
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Davies C, Taylor AJ, Elmi A, Winter J, Liaw J, Grabowska AD, Gundogdu O, Wren BW, Kelly DJ, Dorrell N. Sodium Taurocholate Stimulates Campylobacter jejuni Outer Membrane Vesicle Production via Down-Regulation of the Maintenance of Lipid Asymmetry Pathway. Front Cell Infect Microbiol 2019; 9:177. [PMID: 31192166 PMCID: PMC6549495 DOI: 10.3389/fcimb.2019.00177] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Accepted: 05/09/2019] [Indexed: 12/22/2022] Open
Abstract
Campylobacter jejuni outer membrane vesicles (OMVs) contain numerous virulence-associated proteins including the cytolethal distending toxin and three serine proteases. As C. jejuni lacks the classical virulence-associated secretion systems of other enteric pathogens that deliver effectors directly into target cells, OMVs may have a particularly important role in virulence. C. jejuni OMV production is stimulated by the presence of physiological concentrations of the bile salt sodium taurocholate (ST) through an unknown mechanism. The maintenance of lipid asymmetry (MLA) pathway has been implicated in a novel mechanism for OMV biogenesis, open to regulation by host signals. In this study we investigated the role of the MLA pathway in C. jejuni OMV biogenesis with ST as a potential regulator. OMV production was quantified by analyzing protein and lipid concentrations of OMV preparations and OMV particle counts produced by nanoparticle tracking analysis. Mutation of mlaA which encodes the outer membrane component of the MLA pathway significantly increased OMV production compared to the wild-type strain. Detergent sensitivity and membrane permeability assays confirmed the increased OMV production was not due to changes in membrane stability. The presence of 0.2% (w/v) ST increased wild-type OMV production and reduced OMV size, but did not further stimulate mlaA mutant OMV production or significantly alter mlaA mutant OMV size. qRT-PCR analysis demonstrated that the presence of ST decreased expression of both mlaA and mlaC in C. jejuni wild-type strains 11168 and 488. Collectively the data in this study suggests C. jejuni can regulate OMV production in response to host gut signals through changes in expression of the MLA pathway. As the gut bile composition is dependent on both diet and the microbiota, this study highlights the potential importance of diet and lifestyle factors on the varying disease presentations associated with gut pathogen infection.
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Affiliation(s)
- Cadi Davies
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Aidan J Taylor
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, United Kingdom
| | - Abdi Elmi
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Jody Winter
- School of Science and Technology, Nottingham Trent University, Nottingham, United Kingdom
| | - Janie Liaw
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Anna D Grabowska
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Ozan Gundogdu
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Brendan W Wren
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - David J Kelly
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, United Kingdom
| | - Nick Dorrell
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
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187
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Wong SM, Jackson MD, Akerley BJ. Suppression of Alternative Lipooligosaccharide Glycosyltransferase Activity by UDP-Galactose Epimerase Enhances Murine Lung Infection and Evasion of Serum IgM. Front Cell Infect Microbiol 2019; 9:160. [PMID: 31157175 PMCID: PMC6530457 DOI: 10.3389/fcimb.2019.00160] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Accepted: 04/29/2019] [Indexed: 01/17/2023] Open
Abstract
In pathogens that produce lipooligosaccharide (LOS), sugar residues within the surface-exposed LOS outer core mediate interactions with components of the host immune system, promoting bacterial infection. Many LOS structures are controlled by phase variation mediated by random slipped-strand base mispairing, which can reversibly switch gene expression on or off. Phase variation diversifies the LOS, however its adaptive role is not well-understood. Nontypeable Haemophilus influenzae (NTHi) is an important pathogen that causes a range of illnesses in the upper and lower respiratory tract. In NTHi a phase variable galactosyltransferase encoded by lic2A initiates galactose chain extension of the LOS outer core. The donor substrate for Lic2A, UDP-galactose, is generated from UDP-glucose by UDP-galactose epimerase encoded by galE. Our previous fitness profiling of H. influenzae mutants in a murine lung model showed that the galE mutant had a severe survival defect, while the lic2A mutant's defect was modest, leading us to postulate that unidentified factors act as suppressors of potential defects in a lic2A mutant. Herein we conducted a genome-wide genetic interaction screen to identify genes epistatic on lic2A for survival in the murine lung. An unexpected finding was that galE mutants exhibited restored virulence properties in a lic2A mutant background. We identified an alternative antibody epitope generated by Lic2A in the galE mutant that increased sensitivity to classical complement mediated killing in human serum. Deletion of lic2A or restoration of UDP-galactose synthesis alleviated the galE mutant's virulence defects. These studies indicate that when deprived of its galactosyl substrate, Lic2A acquires an alternative activity leading to increased recognition of NTHi by IgM and decreased survival in the lung model. Biofilm formation was increased by deletion of galE and by increased availability of UDP-GlcNAc precursors that can compete with UDP-galactose production. NTHi's ability to reversibly inactivate lic2A by phase-variation may influence survival in niches of infection in which UDP-Galactose levels are limiting.
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Affiliation(s)
- Sandy M Wong
- Department of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, MS, United States
| | - Mary Darby Jackson
- Department of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, MS, United States
| | - Brian J Akerley
- Department of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, MS, United States
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188
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Huang N, Mao J, Hu M, Wang X, Huo M. Responses to copper stress in the metal-resistant bacterium Cupriavidus gilardii CR3: a whole-transcriptome analysis. J Basic Microbiol 2019; 59:446-457. [PMID: 30900763 DOI: 10.1002/jobm.201800693] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 01/20/2019] [Accepted: 02/06/2019] [Indexed: 11/12/2022]
Abstract
Microbial metal-resistance mechanisms are the basis for the application of microorganisms in metal bioremediation. Despite the available studies of bacterial molecular mechanisms to resistance metals ions (particularly copper), the understanding of bacterial metal resistance is very limited from the transcriptome perspective. Here, responses of the transcriptome (RNA-Seq) was investigated in Cupriavidus gilardii CR3 exposed to 0.5 mM copper, because strain CR3 had a bioremoval capacity of 38.5% for 0.5 mM copper. More than 24 million clean reads were obtained from six libraries and were aligned against the C. gilardii CR3 genome. A total of 310 genes in strain CR3 were significantly differentially expressed under copper stress. Apart from the routine copper resistance operons cus and cop known in previous studies, Gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses of differentially expressed genes indicated that the adenosine triphosphate-binding cassette transporter, amino acid metabolism, and negative chemotaxis collectively contribute to the copper-resistant process. More interestingly, we found that the genes associated with the type III secretion system were induced under copper stress. No such results were reordered in bacteria to date. Overall, this comprehensive network of copper responses is useful for further studies of the molecular mechanisms underlying responses to copper stress in bacteria.
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Affiliation(s)
- Ning Huang
- Engineering Lab for Water Pollution Control and Resources, Northeast Normal University, Changchun, People's Republic of China.,Key Laboratory of Wetland Ecology and Vegetation Restoration of National Environmental Protection, Northeast Normal University, Changchun, People's Republic of China
| | - Juan Mao
- Key Laboratory of Wetland Ecology and Vegetation Restoration of National Environmental Protection, Northeast Normal University, Changchun, People's Republic of China
| | - Mingzhong Hu
- Department of Environmental Engineering, School of Chemical Engineering, Changchun University of Technology, Changchun, People's Republic of China
| | - Xiaoyu Wang
- Engineering Lab for Water Pollution Control and Resources, Northeast Normal University, Changchun, People's Republic of China.,Key Laboratory of Wetland Ecology and Vegetation Restoration of National Environmental Protection, Northeast Normal University, Changchun, People's Republic of China
| | - Mingxin Huo
- Engineering Lab for Water Pollution Control and Resources, Northeast Normal University, Changchun, People's Republic of China
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189
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Huang YMM, Munguia J, Miao Y, Nizet V, McCammon JA. Docking simulation and antibiotic discovery targeting the MlaC protein in Gram-negative bacteria. Chem Biol Drug Des 2019; 93:647-652. [PMID: 30570806 PMCID: PMC6737922 DOI: 10.1111/cbdd.13462] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 11/16/2018] [Accepted: 12/07/2018] [Indexed: 11/28/2022]
Abstract
To maintain the lipid asymmetry of the cell envelope in Gram-negative bacteria, the MlaC protein serves as a lipid transfer factor and delivers phospholipids from the outer to the inner membrane. A strategy of antibiotic discovery is to design a proper compound that can tightly bind to the MlaC protein and inhibit the MlaC function. In this study, we performed virtual screening on multiple MlaC structures obtained from molecular dynamics simulations to identify potential MlaC binders. Our results suggested that clorobiocin is a compound that could bind to the MlaC protein. Through the comparison of the bound geometry between clorobiocin and novobiocin, we pointed out that the methyl-pyrrole group of the noviose sugar in clorobiocin forms hydrophobic interactions with amino acids in the phospholipid binding pocket, which allows the compound to bind deep in the active site. This also explains why clorobiocin shows a tighter binding affinity than novobiocin. Our study highlights a practical path of antibiotic development against Gram-negative bacteria.
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Affiliation(s)
- Yu-ming M. Huang
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093
| | - Jason Munguia
- Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093
| | - Yinglong Miao
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093
| | - Victor Nizet
- Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093
| | - J. Andrew McCammon
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093
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190
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Gerritzen MJH, Martens DE, Uittenbogaard JP, Wijffels RH, Stork M. Sulfate depletion triggers overproduction of phospholipids and the release of outer membrane vesicles by Neisseria meningitidis. Sci Rep 2019; 9:4716. [PMID: 30886228 PMCID: PMC6423031 DOI: 10.1038/s41598-019-41233-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 03/05/2019] [Indexed: 12/21/2022] Open
Abstract
Outer membrane vesicles (OMVs) produced by bacteria are interesting vaccine candidates. OMVs are nanoparticles that contain many immunogenic components, are self-adjuvating, and non-replicative. Despite recent insights in the biogenesis of OMVs, there is no consensus on a conserved mechanism of OMV release and the OMV yield from bacterial cultures remains low. For Neisseria meningitidis, a Gram-negative human pathogen causing meningitis and sepsis, a feasible OMV production method based on triggering OMV release by cysteine depletion has been described. In this study, we investigated the mechanism behind this external trigger for OMV release to improve the production process. Since enhanced OMV release upon cysteine depletion was associated with oxidative stress and redox responses, we investigate the influence of more oxidized sulfur sources on OMV release. We show that N. meningitidis grows similarly on sulfate, the most oxidized sulfur source, and OMV release is triggered by sulfur depletion in general. Sulfate depletion induced increased release of OMVs over cysteine depletion. Proteomics showed that sulfur depletion resulted in oxidative stress responses and upregulated phospholipid and LPS biosynthesis. Furthermore, OMVs produced by sulfur depletion were enriched in phospholipids. Mechanistically, we hypothesize that sulfur depletion results in overproduction of phospholipids causing increased bulging of the outer membrane and subsequent OMV release.
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Affiliation(s)
- Matthias J H Gerritzen
- Institute for Translational Vaccinology (Intravacc), Process Development Bacterial Vaccines, P.O. Box 450, 3720 AL, Bilthoven, The Netherlands
- Wageningen University, Bioprocess Engineering, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Dirk E Martens
- Wageningen University, Bioprocess Engineering, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Joost P Uittenbogaard
- Institute for Translational Vaccinology (Intravacc), Analysis, Delivery, and Formulation, P.O. Box 450, 3720 AL, Bilthoven, The Netherlands
| | - René H Wijffels
- Wageningen University, Bioprocess Engineering, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
- Nord University, Faculty of Biosciences and Aquaculture, P.O. Box 1409, 8049, Bodø, Norway
| | - Michiel Stork
- Institute for Translational Vaccinology (Intravacc), Process Development Bacterial Vaccines, P.O. Box 450, 3720 AL, Bilthoven, The Netherlands.
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191
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Baarda BI, Zielke RA, Le Van A, Jerse AE, Sikora AE. Neisseria gonorrhoeae MlaA influences gonococcal virulence and membrane vesicle production. PLoS Pathog 2019; 15:e1007385. [PMID: 30845186 PMCID: PMC6424457 DOI: 10.1371/journal.ppat.1007385] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 03/19/2019] [Accepted: 02/11/2019] [Indexed: 02/07/2023] Open
Abstract
The six-component maintenance of lipid asymmetry (Mla) system is responsible for retrograde transport of phospholipids, ensuring the barrier function of the Gram-negative cell envelope. Located within the outer membrane, MlaA (VacJ) acts as a channel to shuttle phospholipids from the outer leaflet. We identified Neisseria gonorrhoeae MlaA (ngo2121) during high-throughput proteomic mining for potential therapeutic targets against this medically important human pathogen. Our follow-up phenotypic microarrays revealed that lack of MlaA results in a complex sensitivity phenome. Herein we focused on MlaA function in cell envelope biogenesis and pathogenesis. We demonstrate the existence of two MlaA classes among 21 bacterial species, characterized by the presence or lack of a lipoprotein signal peptide. Purified truncated N. gonorrhoeae MlaA elicited antibodies that cross-reacted with a panel of different Neisseria. Little is known about MlaA expression; we provide the first evidence that MlaA levels increase in stationary phase and under anaerobiosis but decrease during iron starvation. Lack of MlaA resulted in higher cell counts during conditions mimicking different host niches; however, it also significantly decreased colony size. Antimicrobial peptides such as polymyxin B exacerbated the size difference while human defensin was detrimental to mutant viability. Consistent with the proposed role of MlaA in vesicle biogenesis, the ΔmlaA mutant released 1.7-fold more membrane vesicles. Comparative proteomics of cell envelopes and native membrane vesicles derived from ΔmlaA and wild type bacteria revealed enrichment of TadA–which recodes proteins through mRNA editing–as well as increased levels of adhesins and virulence factors. MlaA-deficient gonococci significantly outcompeted (up to 16-fold) wild-type bacteria in the murine lower genital tract, suggesting the growth advantage or increased expression of virulence factors afforded by inactivation of mlaA is advantageous in vivo. Based on these results, we propose N. gonorrhoeae restricts MlaA levels to modulate cell envelope homeostasis and fine-tune virulence. The Gram-negative outer membrane is a formidable barrier, primarily because of its asymmetric composition. A layer of lipopolysaccharide is exposed to the external environment and phospholipids are on the internal face of the outer membrane. MlaA is part of a bacterial system that prevents phospholipid accumulation within the lipopolysaccharide layer. If MlaA is removed, membrane asymmetry is disrupted and bacteria become more vulnerable to certain antimicrobials. Neisseria gonorrhoeae causes millions of infections worldwide annually. A growing number are resistant to available antibiotics. Improving our understanding of gonococcal pathogenicity and basic biological processes is required to facilitate the discovery of new weapons against gonorrhea. We investigated the role of MlaA in N. gonorrhoeae and found that when MlaA was absent, bacteria were more sensitive to antibiotics and human defensins. However, the mutant bacteria produced more membrane vesicles–packages of proteins wrapped in membrane material. Mutant vesicles and cell envelopes were enriched in proteins that contribute to disease. These alterations significantly increased mutant fitness during experimental infection of the female mouse genital tract. Our results provide new insights into the processes N. gonorrhoeae uses to fine-tune its ability to stay fit in the hostile environment of the genital tract.
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Affiliation(s)
- Benjamin I. Baarda
- Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America
| | - Ryszard A. Zielke
- Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America
| | - Adriana Le Van
- Department of Microbiology and Immunology, F. Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
| | - Ann E. Jerse
- Department of Microbiology and Immunology, F. Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
| | - Aleksandra E. Sikora
- Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America
- Vaccine and Gene Therapy Institute, Oregon Health & Science University, Beaverton, Oregon, United States of America
- * E-mail:
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192
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Ricci DP, Silhavy TJ. Outer Membrane Protein Insertion by the β-barrel Assembly Machine. EcoSal Plus 2019; 8:10.1128/ecosalplus.ESP-0035-2018. [PMID: 30869065 PMCID: PMC6419762 DOI: 10.1128/ecosalplus.esp-0035-2018] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
Abstract
Like all outer membrane (OM) constituents, integral OM β-barrel proteins in Gram-negative bacteria are synthesized in the cytoplasm and trafficked to the OM, where they are locally assembled into the growing OM by the ubiquitous β-barrel assembly machine (Bam). While the identities and structures of all essential and accessory Bam components have been determined, the basic mechanism of Bam-assisted OM protein integration remains elusive. Here we review mechanistic analyses of OM β-barrel protein folding and Bam dynamics and summarize recent insights that inform a general model for OM protein recognition and assembly by the Bam complex.
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Affiliation(s)
- Dante P Ricci
- Department of Early Research, Achaogen, Inc., South San Francisco, CA 94080
| | - Thomas J Silhavy
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
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193
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Lonergan ZR, Nairn BL, Wang J, Hsu YP, Hesse LE, Beavers WN, Chazin WJ, Trinidad JC, VanNieuwenhze MS, Giedroc DP, Skaar EP. An Acinetobacter baumannii, Zinc-Regulated Peptidase Maintains Cell Wall Integrity during Immune-Mediated Nutrient Sequestration. Cell Rep 2019; 26:2009-2018.e6. [PMID: 30784584 PMCID: PMC6441547 DOI: 10.1016/j.celrep.2019.01.089] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 12/21/2018] [Accepted: 01/24/2019] [Indexed: 01/10/2023] Open
Abstract
Acinetobacter baumannii is an important nosocomial pathogen capable of causing wound infections, pneumonia, and bacteremia. During infection, A. baumannii must acquire Zn to survive and colonize the host. Vertebrates have evolved mechanisms to sequester Zn from invading pathogens by a process termed nutritional immunity. One of the most upregulated genes during Zn starvation encodes a putative cell wall-modifying enzyme which we named ZrlA. We found that inactivation of zrlA diminished growth of A. baumannii during Zn starvation. Additionally, this mutant strain displays increased cell envelope permeability, decreased membrane barrier function, and aberrant peptidoglycan muropeptide abundances. This altered envelope increases antibiotic efficacy both in vitro and in an animal model of A. baumannii pneumonia. These results establish ZrlA as a crucial link between nutrient metal uptake and cell envelope homeostasis during A. baumannii pathogenesis, which could be targeted for therapeutic development.
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Affiliation(s)
- Zachery R Lonergan
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA; Microbe-Host Interactions Training Program, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Brittany L Nairn
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Jiefei Wang
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA; Department of Chemistry, Indiana University, Bloomington, IN, USA
| | - Yen-Pang Hsu
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA
| | - Laura E Hesse
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA; Microbe-Host Interactions Training Program, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - William N Beavers
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Walter J Chazin
- Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Chemistry, Vanderbilt University, Nashville, TN, USA; Vanderbilt Institute for Infection, Immunology, and Inflammation, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Jonathan C Trinidad
- Department of Chemistry, Indiana University, Bloomington, IN, USA; Laboratory for Biological Mass Spectrometry, Department of Chemistry, Indiana University, Bloomington, IN, USA
| | - Michael S VanNieuwenhze
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA; Department of Chemistry, Indiana University, Bloomington, IN, USA
| | - David P Giedroc
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA; Department of Chemistry, Indiana University, Bloomington, IN, USA
| | - Eric P Skaar
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA; Vanderbilt Institute for Infection, Immunology, and Inflammation, Vanderbilt University Medical Center, Nashville, TN, USA.
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194
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Sharp C, Boinett C, Cain A, Housden NG, Kumar S, Turner K, Parkhill J, Kleanthous C. O-Antigen-Dependent Colicin Insensitivity of Uropathogenic Escherichia coli. J Bacteriol 2019; 201:e00545-18. [PMID: 30510143 PMCID: PMC6351738 DOI: 10.1128/jb.00545-18] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 11/05/2018] [Indexed: 11/20/2022] Open
Abstract
The outer membrane of Gram-negative bacteria presents a significant barrier for molecules entering the cell. Nevertheless, colicins, which are antimicrobial proteins secreted by Escherichia coli, can target other E. coli cells by binding to cell surface receptor proteins and activating their import, resulting in cell death. Previous studies have documented high rates of nonspecific resistance (insensitivity) of various E. coli strains toward colicins that is independent of colicin-specific immunity and is instead associated with lipopolysaccharide (LPS) in the outer membrane. This observation poses a contradiction: why do E. coli strains have colicin-expressing plasmids, which are energetically costly to retain, if cells around them are likely to be naturally insensitive to the colicin they produce? Here, using a combination of transposon sequencing and phenotypic microarrays, we show that colicin insensitivity of uropathogenic E. coli sequence type 131 (ST131) is dependent on the production of its O-antigen but that minor changes in growth conditions render the organism sensitive toward colicins. The reintroduction of O-antigen into E. coli K-12 demonstrated that it is the density of O-antigen that is the dominant factor governing colicin insensitivity. We also show, by microscopy of fluorescently labelled colicins, that growth conditions affect the degree of occlusion by O-antigen of outer membrane receptors but not the clustered organization of receptors. The result of our study demonstrate that environmental conditions play a critical role in sensitizing E. coli toward colicins and that O-antigen in LPS is central to this role.IMPORTANCEEscherichia coli infections can be a major health burden, especially with the organism becoming increasingly resistant to "last-resort" antibiotics such as carbapenems. Although colicins are potent narrow-spectrum antimicrobials with potential as future antibiotics, high levels of naturally occurring colicin insensitivity have been documented which could limit their efficacy. We identify O-antigen-dependent colicin insensitivity in a clinically relevant uropathogenic E. coli strain and show that this insensitivity can be circumvented by minor changes to growth conditions. The results of our study suggest that colicin insensitivity among E. coli organisms has been greatly overestimated, and as a consequence, colicins could in fact be effective species-specific antimicrobials targeting pathogenic E. coli such as uropathogenic E. coli (UPEC).
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Affiliation(s)
- Connor Sharp
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | | | - Amy Cain
- Wellcome Sanger Institute, Hinxton, United Kingdom
- Macquarie University, Sydney, Australia
| | - Nicholas G Housden
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Sandip Kumar
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Keith Turner
- Quadram Institute Bioscience, Norwich, United Kingdom
| | | | - Colin Kleanthous
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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195
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Boinett CJ, Cain AK, Hawkey J, Do Hoang NT, Khanh NNT, Thanh DP, Dordel J, Campbell JI, Lan NPH, Mayho M, Langridge GC, Hadfield J, Chau NVV, Thwaites GE, Parkhill J, Thomson NR, Holt KE, Baker S. Clinical and laboratory-induced colistin-resistance mechanisms in Acinetobacter baumannii. Microb Genom 2019; 5. [PMID: 30720421 PMCID: PMC6421349 DOI: 10.1099/mgen.0.000246] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The increasing incidence and emergence of multi-drug resistant (MDR) Acinetobacter baumannii has become a major global health concern. Colistin is a historic antimicrobial that has become commonly used as a treatment for MDR A. baumannii infections. The increase in colistin usage has been mirrored by an increase in colistin resistance. We aimed to identify the mechanisms associated with colistin resistance in A. baumannii using multiple high-throughput-sequencing technologies, including transposon-directed insertion site sequencing (TraDIS), RNA sequencing (RNAseq) and whole-genome sequencing (WGS) to investigate the genotypic changes of colistin resistance in A. baumannii. Using TraDIS, we found that genes involved in drug efflux (adeIJK), and phospholipid (mlaC, mlaF and mlaD) and lipooligosaccharide synthesis (lpxC and lpsO) were required for survival in sub-inhibitory concentrations of colistin. Transcriptomic (RNAseq) analysis revealed that expression of genes encoding efflux proteins (adeI, adeC, emrB, mexB and macAB) was enhanced in in vitro generated colistin-resistant strains. WGS of these organisms identified disruptions in genes involved in lipid A (lpxC) and phospholipid synthesis (mlaA), and in the baeS/R two-component system (TCS). We additionally found that mutations in the pmrB TCS genes were the primary colistin-resistance-associated mechanisms in three Vietnamese clinical colistin-resistant A. baumannii strains. Our results outline the entire range of mechanisms employed in A. baumannii for resistance against colistin, including drug extrusion and the loss of lipid A moieties by gene disruption or modification.
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Affiliation(s)
- Christine J Boinett
- 1Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK.,2Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam.,3Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, Oxford University, Oxford, UK
| | - Amy K Cain
- 1Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK.,4Malawi-Liverpool-Wellcome Trust Clinical Research Programme, University of Malawi College of Medicine, Blantyre, Malawi
| | - Jane Hawkey
- 5Centre for Systems Genomics, University of Melbourne, Melbourne, Victoria, Australia.,6Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, Victoria, Australia.,7Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Melbourne, Victoria, Australia
| | - Nhu Tran Do Hoang
- 2Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
| | - Nhu Nguyen Thi Khanh
- 8School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Queensland, Australia
| | - Duy Pham Thanh
- 2Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
| | - Janina Dordel
- 1Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK.,9Department of Biology, Drexel University, Philadelphia 19104, PA, USA
| | - James I Campbell
- 2Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam.,3Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, Oxford University, Oxford, UK
| | - Nguyen Phu Huong Lan
- 2Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam.,10Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | - Matthew Mayho
- 1Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK
| | - Gemma C Langridge
- 1Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK.,11Norwich Medical School, University of East Anglia, Norwich, UK
| | - James Hadfield
- 1Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK
| | | | - Guy E Thwaites
- 2Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam.,3Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, Oxford University, Oxford, UK
| | - Julian Parkhill
- 1Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK
| | - Nicholas R Thomson
- 1Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK.,12Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK
| | - Kathryn E Holt
- 5Centre for Systems Genomics, University of Melbourne, Melbourne, Victoria, Australia.,6Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, Victoria, Australia
| | - Stephen Baker
- 2Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam.,13Medicine, The University of Cambridge, Cambridge, UK.,3Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, Oxford University, Oxford, UK
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196
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Royet K, Parisot N, Rodrigue A, Gueguen E, Condemine G. Identification by Tn-seq of Dickeya dadantii genes required for survival in chicory plants. MOLECULAR PLANT PATHOLOGY 2019; 20:287-306. [PMID: 30267562 PMCID: PMC6637903 DOI: 10.1111/mpp.12754] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The identification of the virulence factors of plant-pathogenic bacteria has relied on the testing of individual mutants on plants, a time-consuming process. Transposon sequencing (Tn-seq) is a very powerful method for the identification of the genes required for bacterial growth in their host. We used this method in a soft-rot pathogenic bacterium to identify the genes required for the multiplication of Dickeya dadantii in chicory. About 100 genes were identified showing decreased or increased fitness in the plant. Most had no previously attributed role in plant-bacterium interactions. Following our screening, in planta competition assays confirmed that the uridine monophosphate biosynthesis pathway and the purine biosynthesis pathway were essential to the survival of D. dadantii in the plant, as the mutants ∆carA, ∆purF, ∆purL, ∆guaB and ∆pyrE were unable to survive in the plant in contrast with the wild-type (WT) bacterium. This study also demonstrated that the biosynthetic pathways of leucine, cysteine and lysine were essential for bacterial survival in the plant and that RsmC and GcpA were important in the regulation of the infection process, as the mutants ∆rsmC and ∆gcpA were hypervirulent. Finally, our study showed that D. dadantii flagellin was glycosylated and that this modification conferred fitness to the bacterium during plant infection. Assay by this method of the large collections of environmental pathogenic strains now available will allow an easy and rapid identification of new virulence factors.
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Affiliation(s)
- Kévin Royet
- University of LyonUniversité Lyon 1, INSA de Lyon, CNRS UMR 5240 Microbiologie Adaptation et PathogénieF‐69622VilleurbanneFrance
| | - Nicolas Parisot
- University of LyonINSA‐Lyon, INRA, BF2I, UMR0203F‐69621VilleurbanneFrance
| | - Agnès Rodrigue
- University of LyonUniversité Lyon 1, INSA de Lyon, CNRS UMR 5240 Microbiologie Adaptation et PathogénieF‐69622VilleurbanneFrance
| | - Erwan Gueguen
- University of LyonUniversité Lyon 1, INSA de Lyon, CNRS UMR 5240 Microbiologie Adaptation et PathogénieF‐69622VilleurbanneFrance
| | - Guy Condemine
- University of LyonUniversité Lyon 1, INSA de Lyon, CNRS UMR 5240 Microbiologie Adaptation et PathogénieF‐69622VilleurbanneFrance
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197
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Kamischke C, Fan J, Bergeron J, Kulasekara HD, Dalebroux ZD, Burrell A, Kollman JM, Miller SI. The Acinetobacter baumannii Mla system and glycerophospholipid transport to the outer membrane. eLife 2019; 8:e40171. [PMID: 30638443 PMCID: PMC6365058 DOI: 10.7554/elife.40171] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 01/11/2019] [Indexed: 01/14/2023] Open
Abstract
The outer membrane (OM) of Gram-negative bacteria serves as a selective permeability barrier that allows entry of essential nutrients while excluding toxic compounds, including antibiotics. The OM is asymmetric and contains an outer leaflet of lipopolysaccharides (LPS) or lipooligosaccharides (LOS) and an inner leaflet of glycerophospholipids (GPL). We screened Acinetobacter baumannii transposon mutants and identified a number of mutants with OM defects, including an ABC transporter system homologous to the Mla system in E. coli. We further show that this opportunistic, antibiotic-resistant pathogen uses this multicomponent protein complex and ATP hydrolysis at the inner membrane to promote GPL export to the OM. The broad conservation of the Mla system in Gram-negative bacteria suggests the system may play a conserved role in OM biogenesis. The importance of the Mla system to Acinetobacter baumannii OM integrity and antibiotic sensitivity suggests that its components may serve as new antimicrobial therapeutic targets.
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Affiliation(s)
- Cassandra Kamischke
- Department of Microbiology, University of Washington, Seattle, United States
| | - Junping Fan
- Department of Microbiology, University of Washington, Seattle, United States
| | - Julien Bergeron
- Department of Biochemistry, University of Washington, Seattle, United States
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, United Kingdom
| | | | - Zachary D Dalebroux
- Department of Microbiology, University of Washington, Seattle, United States
| | - Anika Burrell
- Department of Biochemistry, University of Washington, Seattle, United States
| | - Justin M Kollman
- Department of Biochemistry, University of Washington, Seattle, United States
| | - Samuel I Miller
- Department of Microbiology, University of Washington, Seattle, United States
- Department of Genome Sciences, University of Washington, Seattle, United States
- Department of Medicine, University of Washington, Seattle, United States
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198
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Abstract
Gram-negative bacteria have an outer membrane that is positioned at the frontline of the cell's interaction with the environment and that serves as a barrier against noxious molecules including many antibiotics. This protective function mainly relies on lipopolysaccharide, a complex glycolipid located in the outer leaflet of the outer membrane. In this chapter we will first summarize lipopolysaccharide structure, functions and biosynthetic pathway and then we will discuss how it is transported and assembled to the cell surface. This is a remarkably complex process, as amphipathic lipopolysaccharide molecules must traverse three different cellular compartments to reach their final destination.
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199
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Abstract
The Lpp lipoprotein of Escherichia coli is the first identified protein with a covalently linked lipid. It is chemically bound by its C-terminus to murein (peptidoglycan) and inserts by the lipid at the N-terminus into the outer membrane. As the most abundant protein in E. coli (106 molecules per cell) it plays an important role for the integrity of the cell envelope. Lpp represents the type protein of a large variety of lipoproteins found in Gram-negative and Gram-positive bacteria and in archaea that have in common the lipid structure for anchoring the proteins to membranes but otherwise strongly vary in sequence, structure, and function. Predicted lipoproteins in known prokaryotic genomes comprise 2.7% of all proteins. Lipoproteins are modified by a unique phospholipid pathway and transferred from the cytoplasmic membrane into the outer membrane by a special system. They are involved in protein incorporation into the outer membrane, protein secretion across the cytoplasmic membrane, periplasm and outer membrane, signal transduction, conjugation, cell wall metabolism, antibiotic resistance, biofilm formation, and adhesion to host tissues. They are only found in bacteria and function as signal molecules for the innate immune system of vertebrates, where they cause inflammation and elicit innate and adaptive immune response through Toll-like receptors. This review discusses various aspects of Lpp and other lipoproteins of Gram-negative and Gram-positive bacteria and archaea.
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Affiliation(s)
- Volkmar Braun
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Max Planck Ring 5, 72076, Tübingen, Germany.
| | - Klaus Hantke
- IMIT, University of Tuebingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany
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200
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