1
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Carbo CR, Faromiki OG, Nan B. A lytic transglycosylase connects bacterial focal adhesion complexes to the peptidoglycan cell wall. bioRxiv 2024:2024.04.04.588103. [PMID: 38617213 PMCID: PMC11014575 DOI: 10.1101/2024.04.04.588103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
The Gram-negative bacterium Myxococcus xanthus glides on solid surfaces. Dynamic bacterial focal adhesion complexes (bFACs) convert proton motive force from the inner membrane into mechanical propulsion on the cell surface. It is unclear how the mechanical force transmits across the rigid peptidoglycan (PG) cell wall. Here we show that AgmT, a highly abundant lytic PG transglycosylase homologous to Escherichia coli MltG, couples bFACs to PG. Coprecipitation assay and single-particle microscopy reveal that the gliding motors fail to connect to PG and thus are unable to assemble into bFACs in the absence of an active AgmT. Heterologous expression of E. coli MltG restores the connection between PG and bFACs and thus rescues gliding motility in the M. xanthus cells that lack AgmT. Our results indicate that bFACs anchor to AgmT-modified PG to transmit mechanical force across the PG cell wall.
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Affiliation(s)
- Carlos Ramirez Carbo
- Department of Biology, Texas A&M University, College Station, TX 77843, USA
- The Genetics and Genomics Interdisciplinary Program, Texas A&M University, College Station, TX 77843, USA
- C. R. C and O. G. F. contribute equally to this work
| | - Olalekan G. Faromiki
- Department of Biology, Texas A&M University, College Station, TX 77843, USA
- C. R. C and O. G. F. contribute equally to this work
| | - Beiyan Nan
- Department of Biology, Texas A&M University, College Station, TX 77843, USA
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2
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Bongiovanni TR, Latario CJ, Le Cras Y, Trus E, Robitaille S, Swartz K, Schmidtke D, Vincent M, Kosta A, Orth J, Stengel F, Pellarin R, Rocha EPC, Ross BD, Durand E. Assembly of a unique membrane complex in type VI secretion systems of Bacteroidota. Nat Commun 2024; 15:429. [PMID: 38200008 PMCID: PMC10781749 DOI: 10.1038/s41467-023-44426-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Accepted: 12/13/2023] [Indexed: 01/12/2024] Open
Abstract
The type VI secretion system (T6SS) of Gram-negative bacteria inhibits competitor cells through contact-dependent translocation of toxic effector proteins. In Proteobacteria, the T6SS is anchored to the cell envelope through a megadalton-sized membrane complex (MC). However, the genomes of Bacteroidota with T6SSs appear to lack genes encoding homologs of canonical MC components. Here, we identify five genes in Bacteroides fragilis (tssNQOPR) that are essential for T6SS function and encode a Bacteroidota-specific MC. We purify this complex, reveal its dimensions using electron microscopy, and identify a protein-protein interaction network underlying the assembly of the MC including the stoichiometry of the five TssNQOPR components. Protein TssN mediates the connection between the Bacteroidota MC and the conserved baseplate. Although MC gene content and organization varies across the phylum Bacteroidota, no MC homologs are detected outside of T6SS loci, suggesting ancient co-option and functional convergence with the non-homologous MC of Pseudomonadota.
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Affiliation(s)
- Thibault R Bongiovanni
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie, Bioénergies et Biotechnologie (IM2B), Aix-Marseille Université - Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 7255, Institut national de la santé et de la recherche médicale (INSERM), Marseille, France
- Laboratoire de Chimie Bactérienne (LCB), Institut de Microbiologie, Bioénergies et Biotechnologie (IM2B), Aix-Marseille Université - Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 7255, Institut national de la santé et de la recherche médicale (INSERM), Marseille, France
| | - Casey J Latario
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth College, Hanover, NH, 03755, USA
| | - Youn Le Cras
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Microbial Evolutionary Genomics, Paris, France
| | - Evan Trus
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth College, Hanover, NH, 03755, USA
| | - Sophie Robitaille
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth College, Hanover, NH, 03755, USA
| | - Kerry Swartz
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth College, Hanover, NH, 03755, USA
| | - Danica Schmidtke
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth College, Hanover, NH, 03755, USA
- Department of Microbiology, University of Washington, Seattle, WA, 98109, USA
| | - Maxence Vincent
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie, Bioénergies et Biotechnologie (IM2B), Aix-Marseille Université - Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 7255, Institut national de la santé et de la recherche médicale (INSERM), Marseille, France
- Laboratoire de Chimie Bactérienne (LCB), Institut de Microbiologie, Bioénergies et Biotechnologie (IM2B), Aix-Marseille Université - Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 7255, Institut national de la santé et de la recherche médicale (INSERM), Marseille, France
| | - Artemis Kosta
- Microscopy Core Facility, Institut de Microbiologie de la Méditerranée (IMM), FR3479, CNRS, Aix-Marseille University, Marseille, France
| | - Jan Orth
- Department of Biology, University of Konstanz, Universitätsstraße 10, 78457, Konstanz, Germany
- Konstanz Research School Chemical Biology, University of Konstanz, Universitätsstraße 10, 78457, Konstanz, Germany
| | - Florian Stengel
- Department of Biology, University of Konstanz, Universitätsstraße 10, 78457, Konstanz, Germany
- Konstanz Research School Chemical Biology, University of Konstanz, Universitätsstraße 10, 78457, Konstanz, Germany
| | - Riccardo Pellarin
- Molecular Microbiology and Structural Biochemistry (MMSB, UMR 5086), CNRS & University of Lyon, 7 Passage du Vercors, 69007, Lyon, France
| | - Eduardo P C Rocha
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Microbial Evolutionary Genomics, Paris, France
| | - Benjamin D Ross
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth College, Hanover, NH, 03755, USA.
- Department of Microbiology, University of Washington, Seattle, WA, 98109, USA.
| | - Eric Durand
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie, Bioénergies et Biotechnologie (IM2B), Aix-Marseille Université - Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 7255, Institut national de la santé et de la recherche médicale (INSERM), Marseille, France.
- Laboratoire de Chimie Bactérienne (LCB), Institut de Microbiologie, Bioénergies et Biotechnologie (IM2B), Aix-Marseille Université - Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 7255, Institut national de la santé et de la recherche médicale (INSERM), Marseille, France.
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3
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Santin YG, Cascales E. Measure of Peptidoglycan Degradation Activity. Methods Mol Biol 2024; 2715:197-205. [PMID: 37930529 DOI: 10.1007/978-1-0716-3445-5_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2023]
Abstract
Most bacterial secretion systems are large machines that cross the cell envelope to deliver effectors outside the cell or directly into target cells. The peptidoglycan layer can therefore represent a physical barrier for the assembly of these large machines. Secretion systems and their counterparts such as type IV pili, flagella, and conjugation machines have therefore evolved or hijacked enzymes with peptidoglycan degradation activity. These enzymes are usually glycoside hydrolases that cleave the glycan chains of the peptidoglycan. Their activities are spatially controlled to avoid cell lysis and to create local rearrangement of the cell wall. In addition, peptidoglycan hydrolases may not be only required for the proper assembly of the secretion systems but may directly participate to the release of the effectors. Finally, several antibacterial effectors possess peptidoglycan degradation activity that damage the cell wall once delivered in the target cell. Here, we describe protocols to test the peptidoglycan degradation activity of these proteins in vitro and in solution.
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Affiliation(s)
- Yoann G Santin
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, UMR7255, Institut de Microbiologie de la Méditerranée, Aix-Marseille Univ, CNRS, Marseille, France
- de Duve Institute, UCLouvain, Brussels, Belgium
| | - Eric Cascales
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, UMR7255, Institut de Microbiologie de la Méditerranée, Aix-Marseille Univ, CNRS, Marseille, France.
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4
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Kandolo O, Cherrak Y, Filella-Merce I, Le Guenno H, Kosta A, Espinosa L, Santucci P, Verthuy C, Lebrun R, Nilges M, Pellarin R, Durand E. Acinetobacter type VI secretion system comprises a non-canonical membrane complex. PLoS Pathog 2023; 19:e1011687. [PMID: 37769028 PMCID: PMC10564176 DOI: 10.1371/journal.ppat.1011687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 10/10/2023] [Accepted: 09/14/2023] [Indexed: 09/30/2023] Open
Abstract
A. baumannii can rapidly acquire new resistance mechanisms and persist on abiotic surface, enabling the colonization of asymptomatic human host. In Acinetobacter the type VI secretion system (T6SS) is involved in twitching, surface motility and is used for interbacterial competition allowing the bacteria to uptake DNA. A. baumannii possesses a T6SS that has been well studied for its regulation and specific activity, but little is known concerning its assembly and architecture. The T6SS nanomachine is built from three architectural sub-complexes. Unlike the baseplate (BP) and the tail-tube complex (TTC), which are inherited from bacteriophages, the membrane complex (MC) originates from bacteria. The MC is the most external part of the T6SS and, as such, is subjected to evolution and adaptation. One unanswered question on the MC is how such a gigantesque molecular edifice is inserted and crosses the bacterial cell envelope. The A. baumannii MC lacks an essential component, the TssJ lipoprotein, which anchors the MC to the outer membrane. In this work, we studied how A. baumannii compensates the absence of a TssJ. We have characterized for the first time the A. baumannii's specific T6SS MC, its unique characteristic, its membrane localization, and assembly dynamics. We also defined its composition, demonstrating that its biogenesis employs three Acinetobacter-specific envelope-associated proteins that define an intricate network leading to the assembly of a five-proteins membrane super-complex. Our data suggest that A. baumannii has divided the function of TssJ by (1) co-opting a new protein TsmK that stabilizes the MC and by (2) evolving a new domain in TssM for homo-oligomerization, a prerequisite to build the T6SS channel. We believe that the atypical species-specific features we report in this study will have profound implication in our understanding of the assembly and evolutionary diversity of different T6SSs, that warrants future investigation.
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Affiliation(s)
- Ona Kandolo
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie, Bioénergies and Biotechnologie (IM2B), Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS)-UMR 7255, Marseille, France
| | - Yassine Cherrak
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie, Bioénergies and Biotechnologie (IM2B), Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS)-UMR 7255, Marseille, France
| | - Isaac Filella-Merce
- Institut Pasteur, Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, Paris, France
- Sorbonne Université, Collège doctoral, Paris, France
| | - Hugo Le Guenno
- Microscopy Core Facility, Aix Marseille Univ, CNRS, Institut de Microbiologie de la Méditerranée, Marseille Cedex 20, France
| | - Artemis Kosta
- Microscopy Core Facility, Aix Marseille Univ, CNRS, Institut de Microbiologie de la Méditerranée, Marseille Cedex 20, France
| | - Leon Espinosa
- Laboratoire de Chimie Bactérienne (LCB), Institut de Microbiologie, Bioénergies and Biotechnologie (IM2B), Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France
| | - Pierre Santucci
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie, Bioénergies and Biotechnologie (IM2B), Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS)-UMR 7255, Marseille, France
| | - Christophe Verthuy
- Proteomic Core Facility IMM, Marseille Protéomique (MaP), Aix Marseille Univ, Marseille Cedex 20, France
| | - Régine Lebrun
- Proteomic Core Facility IMM, Marseille Protéomique (MaP), Aix Marseille Univ, Marseille Cedex 20, France
| | - Michael Nilges
- Institut Pasteur, Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, Paris, France
| | - Riccardo Pellarin
- Institut Pasteur, Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, Paris, France
| | - Eric Durand
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie, Bioénergies and Biotechnologie (IM2B), Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS)-UMR 7255, Marseille, France
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie, Bioénergies and Biotechnologie (IM2B), Aix-Marseille Université, Institut National de la Santé et de la Recherche Médicale (INSERM), Marseille, France
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5
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Allsopp LP, Bernal P. Killing in the name of: T6SS structure and effector diversity. Microbiology (Reading) 2023; 169:001367. [PMID: 37490402 PMCID: PMC10433429 DOI: 10.1099/mic.0.001367] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 07/12/2023] [Indexed: 07/27/2023]
Abstract
The life of bacteria is challenging, to endure bacteria employ a range of mechanisms to optimize their environment, including deploying the type VI secretion system (T6SS). Acting as a bacterial crossbow, this system delivers effectors responsible for subverting host cells, killing competitors and facilitating general secretion to access common goods. Due to its importance, this lethal machine has been evolutionarily maintained, disseminated and specialized to fulfil these vital functions. In fact, T6SS structural clusters are present in over 25 % of Gram-negative bacteria, varying in number from one to six different genetic clusters per organism. Since its discovery in 2006, research on the T6SS has rapidly progressed, yielding remarkable breakthroughs. The identification and characterization of novel components of the T6SS, combined with biochemical and structural studies, have revealed fascinating mechanisms governing its assembly, loading, firing and disassembly processes. Recent findings have also demonstrated the efficacy of this system against fungal and Gram-positive cells, expanding its scope. Ongoing research continues to uncover an extensive and expanding repertoire of T6SS effectors, the genuine mediators of T6SS function. These studies are shedding light on new aspects of the biology of prokaryotic and eukaryotic organisms. This review provides a comprehensive overview of the T6SS, highlighting recent discoveries of its structure and the diversity of its effectors. Additionally, it injects a personal perspective on avenues for future research, aiming to deepen our understanding of this combative system.
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Affiliation(s)
- Luke P. Allsopp
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Patricia Bernal
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla 41012, Spain
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6
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Choi U, Park SH, Lee HB, Son JE, Lee CR. Coordinated and Distinct Roles of Peptidoglycan Carboxypeptidases DacC and DacA in Cell Growth and Shape Maintenance under Stress Conditions. Microbiol Spectr 2023; 11:e0001423. [PMID: 37098975 PMCID: PMC10269652 DOI: 10.1128/spectrum.00014-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Accepted: 04/09/2023] [Indexed: 04/27/2023] Open
Abstract
Peptidoglycan (PG) is an essential bacterial architecture pivotal for shape maintenance and adaptation to osmotic stress. Although PG synthesis and modification are tightly regulated under harsh environmental stresses, few related mechanisms have been investigated. In this study, we aimed to investigate the coordinated and distinct roles of the PG dd-carboxypeptidases (DD-CPases) DacC and DacA in cell growth under alkaline and salt stresses and shape maintenance in Escherichia coli. We found that DacC is an alkaline DD-CPase, the enzyme activity and protein stability of which are significantly enhanced under alkaline stress. Both DacC and DacA were required for bacterial growth under alkaline stress, whereas only DacA was required for growth under salt stress. Under normal growth conditions, only DacA was necessary for cell shape maintenance, while under alkaline stress conditions, both DacA and DacC were necessary for cell shape maintenance, but their roles were distinct. Notably, all of these roles of DacC and DacA were independent of ld-transpeptidases, which are necessary for the formation of PG 3-3 cross-links and covalent bonds between PG and the outer membrane lipoprotein Lpp. Instead, DacC and DacA interacted with penicillin-binding proteins (PBPs)-dd-transpeptidases-mostly in a C-terminal domain-dependent manner, and these interactions were necessary for most of their roles. Collectively, our results demonstrate the coordinated and distinct novel roles of DD-CPases in bacterial growth and shape maintenance under stress conditions and provide novel insights into the cellular functions of DD-CPases associated with PBPs. IMPORTANCE Most bacteria have a peptidoglycan architecture for cell shape maintenance and protection against osmotic challenges. Peptidoglycan dd-carboxypeptidases control the amount of pentapeptide substrates, which are used in the formation of 4-3 cross-links by the peptidoglycan synthetic dd-transpeptidases, penicillin-binding proteins (PBPs). Seven dd-carboxypeptidases exist in Escherichia coli, but the physiological significance of their redundancy and their roles in peptidoglycan synthesis are poorly understood. Here, we showed that DacC is an alkaline dd-carboxypeptidase for which both protein stability and enzyme activity are significantly enhanced at high pH. Strikingly, dd-carboxypeptidases DacC and DacA physically interacted with PBPs, and these interactions were necessary for cell shape maintenance as well as growth under alkaline and salt stresses. Thus, cooperation between dd-carboxypeptidases and PBPs may allow E. coli to overcome various stresses and to maintain cell shape.
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Affiliation(s)
- Umji Choi
- Department of Biological Sciences, Myongji University, Yongin, Gyeonggido, Republic of Korea
| | - Si Hyoung Park
- Department of Biological Sciences, Myongji University, Yongin, Gyeonggido, Republic of Korea
| | - Han Byeol Lee
- Department of Biological Sciences, Myongji University, Yongin, Gyeonggido, Republic of Korea
| | - Ji Eun Son
- Department of Biological Sciences, Myongji University, Yongin, Gyeonggido, Republic of Korea
| | - Chang-Ro Lee
- Department of Biological Sciences, Myongji University, Yongin, Gyeonggido, Republic of Korea
- The Natural Science Research Institute, Myongji University, Yongin, Gyeonggido, Republic of Korea
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7
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Boamah D, Gilmore M, Bourget S, Ghosh A, Hossain M, Vogel J, Cava F, O’Connor T. Peptidoglycan deacetylation controls type IV secretion and the intracellular survival of the bacterial pathogen Legionella pneumophila. Proc Natl Acad Sci U S A 2023; 120:e2119658120. [PMID: 37252954 PMCID: PMC10266036 DOI: 10.1073/pnas.2119658120] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 04/18/2023] [Indexed: 06/01/2023] Open
Abstract
Peptidoglycan is a critical component of the bacteria cell envelope. Remodeling of the peptidoglycan is required for numerous essential cellular processes and has been linked to bacterial pathogenesis. Peptidoglycan deacetylases that remove the acetyl group of the N-acetylglucosamine (NAG) subunit protect bacterial pathogens from immune recognition and digestive enzymes secreted at the site of infection. However, the full extent of this modification on bacterial physiology and pathogenesis is not known. Here, we identify a polysaccharide deacetylase of the intracellular bacterial pathogen Legionella pneumophila and define a two-tiered role for this enzyme in Legionella pathogenesis. First, NAG deacetylation is important for the proper localization and function of the Type IVb secretion system, linking peptidoglycan editing to the modulation of host cellular processes through the action of secreted virulence factors. As a consequence, the Legionella vacuole mis-traffics along the endocytic pathway to the lysosome, preventing the formation of a replication permissive compartment. Second, within the lysosome, the inability to deacetylate the peptidoglycan renders the bacteria more sensitive to lysozyme-mediated degradation, resulting in increased bacterial death. Thus, the ability to deacetylate NAG is important for bacteria to persist within host cells and in turn, Legionella virulence. Collectively, these results expand the function of peptidoglycan deacetylases in bacteria, linking peptidoglycan editing, Type IV secretion, and the intracellular fate of a bacterial pathogen.
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Affiliation(s)
- David Boamah
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD21205
| | - Michael C. Gilmore
- Department of Molecular Biology, Laboratory for Molecular Infection Medicine Sweden, Umeå Centre for Microbial Research, Umeå University, Umeå90187, Sweden
| | - Sarah Bourget
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD21205
| | - Anushka Ghosh
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD21205
| | - Mohammad J. Hossain
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD21205
| | - Joseph P. Vogel
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO63110
| | - Felipe Cava
- Department of Molecular Biology, Laboratory for Molecular Infection Medicine Sweden, Umeå Centre for Microbial Research, Umeå University, Umeå90187, Sweden
| | - Tamara J. O’Connor
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD21205
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8
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Weaver A, Taguchi A, Dörr T. Masters of Misdirection: Peptidoglycan Glycosidases in Bacterial Growth. J Bacteriol 2023; 205:e0042822. [PMID: 36757204 PMCID: PMC10029718 DOI: 10.1128/jb.00428-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023] Open
Abstract
The dynamic composition of the peptidoglycan cell wall has been the subject of intense research for decades, yet how bacteria coordinate the synthesis of new peptidoglycan with the turnover and remodeling of existing peptidoglycan remains elusive. Diversity and redundancy within peptidoglycan synthases and peptidoglycan autolysins, enzymes that degrade peptidoglycan, have often made it challenging to assign physiological roles to individual enzymes and determine how those activities are regulated. For these reasons, peptidoglycan glycosidases, which cleave within the glycan strands of peptidoglycan, have proven veritable masters of misdirection over the years. Unlike many of the broadly conserved peptidoglycan synthetic complexes, diverse bacteria can employ unrelated glycosidases to achieve the same physiological outcome. Additionally, although the mechanisms of action for many individual enzymes have been characterized, apparent conserved homologs in other organisms can exhibit an entirely different biochemistry. This flexibility has been recently demonstrated in the context of three functions critical to vegetative growth: (i) release of newly synthesized peptidoglycan strands from their membrane anchors, (ii) processing of peptidoglycan turned over during cell wall expansion, and (iii) removal of peptidoglycan fragments that interfere with daughter cell separation during cell division. Finally, the regulation of glycosidase activity during these cell processes may be a cumulation of many factors, including protein-protein interactions, intrinsic substrate preferences, substrate availability, and subcellular localization. Understanding the true scope of peptidoglycan glycosidase activity will require the exploration of enzymes from diverse organisms with equally diverse growth and division strategies.
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Affiliation(s)
- Anna Weaver
- Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts, USA
| | - Atsushi Taguchi
- SANKEN (The Institute of Scientific and Industrial Research), Osaka University, Ibaraki, Osaka, Japan
| | - Tobias Dörr
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, USA
- Department of Microbiology, Cornell University, Ithaca, New York, USA
- Cornell Institute of Host-Microbe Interactions and Disease, Cornell University, Ithaca, New York, USA
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9
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Santoriello F, Pukatzki S. Type VI Secretion Systems: Environmental and Intra-host Competition of Vibrio cholerae. Adv Exp Med Biol 2023; 1404:41-63. [PMID: 36792870 DOI: 10.1007/978-3-031-22997-8_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
The Vibrio Type VI Secretion System (T6SS) is a harpoon-like nanomachine that serves as a defense system and is encoded by approximately 25% of all gram-negative bacteria. In this chapter, we describe the structure of the T6SS in different Vibrio species and outline how the use of different T6SS effector and immunity proteins control kin selection. We summarize the genetic loci that encode the structural elements that make up the Vibrio T6SSs and how these gene clusters are regulated. Finally, we provide insights into T6SS-based competitive dynamics, the role of T6SS genetic exchange in those competitive dynamics, and roles for the Vibrio T6SS in virulence.
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10
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Bachert BA, Bozue JA. Peptidoglycan enzymes of Francisella: Roles in cell morphology and pathogenesis, and potential as therapeutic targets. Front Microbiol 2023; 13:1099312. [PMID: 36713212 PMCID: PMC9877522 DOI: 10.3389/fmicb.2022.1099312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 12/28/2022] [Indexed: 01/13/2023] Open
Abstract
Peptidoglycan, found within the cell wall of bacteria, is a structure critical for maintaining cell morphology and providing a protective barrier in diverse environments. Peptidoglycan is a remarkably dynamic structure that is constantly remodeled during cell growth and division by various peptidoglycan enzymes. Numerous peptidoglycan enzymes have been characterized from diverse bacteria and are highly sought after as targets for therapeutics. However, very little is known about these enzymes within the biothreat agent Francisella tularensis. As the causative agent of tularemia, F. tularensis is classified as a category A biothreat pathogen, in part due to its low infectious dose and lack of FDA-approved vaccine. Many bacterial species encode multiple peptidoglycan enzymes with redundant functions that allow for compensation if one of the enzymes are inactivated. In contrast, F. tularensis appears to lack this redundancy, indicating peptidoglycan enzymes may be completely essential for growth and could be exploited as targets for medical countermeasures. Indeed, several peptidoglycan enzymes in F. tularensis have been shown to play important roles in cell division, cell morphology, virulence, and modulation of host response. The aim of this review is to summarize findings from the current literature on peptidoglycan enzymes present in Francisella and discuss areas where future research efforts might be directed. We conclude that Francisella harbors a distinct set of peptidoglycan enzymes important for cell growth and virulence and represent potentially valuable targets for the development of novel therapeutics.
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11
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Gabbert AD, Mydosh JL, Talukdar PK, Gloss LM, McDermott JE, Cooper KK, Clair GC, Konkel ME. The Missing Pieces: The Role of Secretion Systems in Campylobacter jejuni Virulence. Biomolecules 2023; 13:135. [PMID: 36671522 PMCID: PMC9856085 DOI: 10.3390/biom13010135] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 12/29/2022] [Accepted: 01/05/2023] [Indexed: 01/10/2023] Open
Abstract
Campylobacter jejuni is likely the most common bacterial cause of gastroenteritis worldwide, responsible for millions of cases of inflammatory diarrhea characterized by severe abdominal cramps and blood in the stool. Further, C. jejuni infections are associated with post-infection sequelae in developed countries and malnutrition and growth-stunting in low- and middle-income countries. Despite the increasing prevalence of the disease, campylobacteriosis, and the recognition that this pathogen is a serious health threat, our understanding of C. jejuni pathogenesis remains incomplete. In this review, we focus on the Campylobacter secretion systems proposed to contribute to host-cell interactions and survival in the host. Moreover, we have applied a genomics approach to defining the structural and mechanistic features of C. jejuni type III, IV, and VI secretion systems. Special attention is focused on the flagellar type III secretion system and the prediction of putative effectors, given that the proteins exported via this system are essential for host cell invasion and the inflammatory response. We conclude that C. jejuni does not possess a type IV secretion system and relies on the type III and type VI secretion systems to establish a niche and potentiate disease.
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Affiliation(s)
- Amber D. Gabbert
- School of Molecular Biosciences, College of Veterinary Sciences, Washington State University, Pullman, WA 99164, USA
| | - Jennifer L. Mydosh
- School of Animal and Comparative Biomedical Sciences, The University of Arizona, Tucson, AZ 85721, USA
| | - Prabhat K. Talukdar
- School of Molecular Biosciences, College of Veterinary Sciences, Washington State University, Pullman, WA 99164, USA
| | - Lisa M. Gloss
- School of Molecular Biosciences, College of Veterinary Sciences, Washington State University, Pullman, WA 99164, USA
| | - Jason E. McDermott
- Integrative Omics, Pacific Northwest National Laboratory, Richland, WA 99354, USA
| | - Kerry K. Cooper
- School of Animal and Comparative Biomedical Sciences, The University of Arizona, Tucson, AZ 85721, USA
| | - Geremy C. Clair
- Integrative Omics, Pacific Northwest National Laboratory, Richland, WA 99354, USA
| | - Michael E. Konkel
- School of Molecular Biosciences, College of Veterinary Sciences, Washington State University, Pullman, WA 99164, USA
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12
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Martinez-Bond EA, Soriano BM, Williams AH. The mechanistic landscape of Lytic transglycosylase as targets for antibacterial therapy. Curr Opin Struct Biol 2022; 77:102480. [PMID: 36323133 DOI: 10.1016/j.sbi.2022.102480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 08/24/2022] [Accepted: 09/09/2022] [Indexed: 12/14/2022]
Abstract
Lytic transglycosylases (Ltgs) are glycan strand cleaving enzymes whose role is poorly understood in the genesis of the bacterial envelope. They play multiple roles in all stages of a bacterial life cycle, by creating holes in the peptidoglycan that is necessary for cell division and separation. Here, we review recent advances in understanding the suitability of Ltgs as antibacterial drug targets. We specifically highlight a known inhibitor bulgecin A that is able to inhibit the function of structurally diverse Ltgs, as well as synergize with beta-lactams to improve its efficacy in antibiotic insensitive strains. Discovery of new antibiotics or new targets has been challenging. These studies could provide a viable path toward designing broad-spectrum inhibitors that targets Ltgs.
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Affiliation(s)
- Elizabeth A Martinez-Bond
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA, 94158, USA. https://twitter.com/bondlizbond
| | - Berliza M Soriano
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA, 94158, USA. https://twitter.com/AWilliamslab
| | - Allison H Williams
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA, 94158, USA; Chan Zuckerberg Biohub, San Francisco, CA, USA.
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13
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Cui Y, Pei TT, Liang X, Li H, Zheng HY, Dong T. Heterologous Assembly of the Type VI Secretion System Empowers Laboratory Escherichia coli with Antimicrobial and Cell Penetration Capabilities. Appl Environ Microbiol 2022;:e0130522. [PMID: 36154120 DOI: 10.1128/aem.01305-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The synthetic biology toolbox has amassed a vast number of diverse functional modules, but protein translocation modules for cell penetration and cytosol-to-cytosol delivery remain relatively scarce. The type VI secretion system (T6SS), commonly found in many Gram-negative pathogens, functions as a contractile device to translocate protein toxins to prokaryotic and eukaryotic cells. Here, we have assembled the T6SS of Aeromonas dhakensis, an opportunistic waterborne pathogen, in the common laboratory strain Escherichia coli BL21(DE3). We constructed a series of plasmids (pT6S) carrying the T6SS structural and effector genes under native or tetracycline-inducible promoters, the latter for controlled expression. Using fluorescence microscopy and biochemical analyses, we demonstrate a functional T6SS in E. coli capable of secreting proteins directly into the cytosol of neighboring bacteria and outcompeting a number of drug-resistant pathogens. The heterologous assembly of T6SS not only confers the lab workhorse E. coli with the cytosol-to-cytosol protein delivery capability but also demonstrates the potential for harnessing the T6SS of various pathogens for general protein delivery and antibacterial applications. IMPORTANCE The T6SS is a powerful and versatile protein delivery system. However, the complexity of its macromolecular structure and gene regulation makes it not a trivial task to reconstitute the T6SSs of pathogens in a nonpathogenic host. In this study, we have assembled an inducible T6SS in E. coli BL21(DE3) and demonstrated its functions in protein delivery and antimicrobial activities. The engineered T6SS empowers E. coli to deliver protein cargos into a wide range of prokaryotic and eukaryotic cells.
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14
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Lin L, Capozzoli R, Ferrand A, Plum M, Vettiger A, Basler M. Subcellular localization of Type VI secretion system assembly in response to cell–cell contact. EMBO J 2022; 41:e108595. [PMID: 35634969 PMCID: PMC9251886 DOI: 10.15252/embj.2021108595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 04/18/2022] [Accepted: 04/29/2022] [Indexed: 11/13/2022] Open
Abstract
Bacteria require a number of systems, including the type VI secretion system (T6SS), for interbacterial competition and pathogenesis. The T6SS is a large nanomachine that can deliver toxins directly across membranes of proximal target cells. Since major reassembly of T6SS is necessary after each secretion event, accurate timing and localization of T6SS assembly can lower the cost of protein translocation. Although critically important, mechanisms underlying spatiotemporal regulation of T6SS assembly remain poorly understood. Here, we used super‐resolution live‐cell imaging to show that while Acinetobacter and Burkholderia thailandensis can assemble T6SS at any site, a significant subset of T6SS assemblies localizes precisely to the site of contact between neighboring bacteria. We identified a class of diverse, previously uncharacterized, periplasmic proteins required for this dynamic localization of T6SS to cell–cell contact (TslA). This precise localization is also dependent on the outer membrane porin OmpA. Our analysis links transmembrane communication to accurate timing and localization of T6SS assembly as well as uncovers a pathway allowing bacterial cells to respond to cell–cell contact during interbacterial competition.
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Affiliation(s)
- Lin Lin
- Biozentrum University of Basel Basel Switzerland
| | | | - Alexia Ferrand
- Biozentrum Imaging Core Facility University of Basel Basel Switzerland
| | - Miro Plum
- Biozentrum University of Basel Basel Switzerland
| | | | - Marek Basler
- Biozentrum University of Basel Basel Switzerland
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15
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Zhang S, Gu S, Rycroft P, Ruaudel F, Delolme F, Robert X, Ballut L, Pickersgill RW, Shevchik VE. Scaffolding Protein GspB/OutB Facilitates Assembly of the Dickeya dadantii Type 2 Secretion System by Anchoring the Outer Membrane Secretin Pore to the Inner Membrane and to the Peptidoglycan Cell Wall. mBio 2022;:e0025322. [PMID: 35546537 DOI: 10.1128/mbio.00253-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The phytopathogenic proteobacterium Dickeya dadantii secretes an array of plant cell wall-degrading enzymes and other virulence factors via the type 2 secretion system (T2SS). T2SSs are widespread among important plant, animal, and human bacterial pathogens. This multiprotein complex spans the double membrane cell envelope and secretes fully folded proteins through a large outer membrane pore formed by 15 subunits of the secretin GspD. Secretins are also found in the type 3 secretion system and the type 4 pili. Usually, specialized lipoproteins termed pilotins assist the targeting and assembly of secretins into the outer membrane. Here, we show that in D. dadantii, the pilotin acts in concert with the scaffolding protein GspB. Deletion of gspB profoundly impacts secretin assembly, pectinase secretion, and virulence. Structural studies reveal that GspB possesses a conserved periplasmic homology region domain that interacts directly with the N-terminal secretin domain. Site-specific photo-cross-linking unravels molecular details of the GspB-GspD complex in vivo. We show that GspB facilitates outer membrane targeting and assembly of the secretin pores and anchors them to the inner membrane while the C-terminal extension of GspB provides a scaffold for the secretin channel in the peptidoglycan cell wall. Phylogenetic analysis shows that in other bacteria, GspB homologs vary in length and domain composition and act in concert with either a cognate ATPase GspA or the pilotin GspS.
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16
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Weaver AI, Alvarez L, Rosch KM, Ahmed A, Wang GS, vanNieuwenhze MS, Cava F, Dörr T. Lytic transglycosylases mitigate periplasmic crowding by degrading soluble cell wall turnover products. eLife 2022; 11:73178. [PMID: 35073258 PMCID: PMC8820737 DOI: 10.7554/elife.73178] [Citation(s) in RCA: 39] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 01/23/2022] [Indexed: 11/25/2022] Open
Abstract
The peptidoglycan cell wall is a predominant structure of bacteria, determining cell shape and supporting survival in diverse conditions. Peptidoglycan is dynamic and requires regulated synthesis of new material, remodeling, and turnover – or autolysis – of old material. Despite exploitation of peptidoglycan synthesis as an antibiotic target, we lack a fundamental understanding of how peptidoglycan synthesis and autolysis intersect to maintain the cell wall. Here, we uncover a critical physiological role for a widely misunderstood class of autolytic enzymes, lytic transglycosylases (LTGs). We demonstrate that LTG activity is essential to survival by contributing to periplasmic processes upstream and independent of peptidoglycan recycling. Defects accumulate in Vibrio cholerae LTG mutants due to generally inadequate LTG activity, rather than absence of specific enzymes, and essential LTG activities are likely independent of protein-protein interactions, as heterologous expression of a non-native LTG rescues growth of a conditional LTG-null mutant. Lastly, we demonstrate that soluble, uncrosslinked, endopeptidase-dependent peptidoglycan chains, also detected in the wild-type, are enriched in LTG mutants, and that LTG mutants are hypersusceptible to the production of diverse periplasmic polymers. Collectively, our results suggest that LTGs prevent toxic crowding of the periplasm with synthesis-derived peptidoglycan polymers and, contrary to prevailing models, that this autolytic function can be temporally separate from peptidoglycan synthesis.
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Affiliation(s)
| | - Laura Alvarez
- Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University
| | - Kelly M Rosch
- Weill Institute for Cell and Molecular Biology, Cornell University
| | - Asraa Ahmed
- Weill Institute for Cell and Molecular Biology, Cornell University
| | | | | | - Felipe Cava
- The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University
| | - Tobias Dörr
- Weill Institute for Cell and Molecular Biology, Cornell University
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17
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Abstract
Most bacteria are protected from environmental offenses by a cell wall consisting of strong yet elastic peptidoglycan. The cell wall is essential for preserving bacterial morphology and viability, and thus the enzymes involved in the production and turnover of peptidoglycan have become preferred targets for many of our most successful antibiotics. In the past decades, Vibrio cholerae, the gram-negative pathogen causing the diarrheal disease cholera, has become a major model for understanding cell wall genetics, biochemistry, and physiology. More than 100 articles have shed light on novel cell wall genetic determinants, regulatory links, and adaptive mechanisms. Here we provide the first comprehensive review of V. cholerae's cell wall biology and genetics. Special emphasis is placed on the similarities and differences with Escherichia coli, the paradigm for understanding cell wall metabolism and chemical structure in gram-negative bacteria.
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Affiliation(s)
- Laura Alvarez
- Department of Molecular Biology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå SE-90187, Sweden;
| | - Sara B Hernandez
- Department of Molecular Biology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå SE-90187, Sweden;
| | - Felipe Cava
- Department of Molecular Biology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå SE-90187, Sweden;
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18
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García-Ramos M, de la Mora J, Ballado T, Camarena L, Dreyfus G. Modulation of the enzymatic activity of the flagellar lytic transglycosylase SltF by rod components, and the scaffolding protein FlgJ in Rhodobacter sphaeroides. J Bacteriol 2021;:JB0037221. [PMID: 34309398 DOI: 10.1128/JB.00372-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Macromolecular cell-envelope-spanning structures such as the bacterial flagellum must traverse the cell wall. Lytic transglycosylases enzymes are capable of enlarging gaps in the peptidoglycan meshwork to allow the efficient assembly of supramolecular complexes. In the periplasmic space, the assembly of the flagellar rod requires the scaffold protein FlgJ, which includes a muramidase domain in the canonical models Salmonella enterica and Escherichia coli. In contrast, in Rhodobacter sphaeroides, FlgJ and the dedicated flagellar lytic transglycosylase SltF are separate entities that interact in the periplasm. In this study we show that sltF is expressed along with the genes encoding the early components of the flagellar hierarchy that include the hook-basal body proteins, making SltF available during the rod assembly. Protein-protein interaction experiments demonstrated that SltF interacts with the rod proteins FliE, FlgB, FlgC, FlgF and FlgG through its C-terminal region. A deletion analysis that divides the C-terminus in two halves revealed that the interacting regions for most of the rod proteins are not redundant. Our results also show that the presence of the rod proteins FliE, FlgB, FlgC, and FlgF displace the previously reported SltF-FlgJ interaction. In addition, we observed modulation of the transglycosylase activity of SltF mediated by FlgB and FlgJ that could be relevant to coordinate rod assembly with cell wall remodeling. In summary, different mechanisms regulate the flagellar lytic transglycosylase, SltF ensuring a timely transcription, a proper localization and a controlled enzymatic activity. Importance Several mechanisms participate in the assembly of cell-envelope-spanning macromolecular structures. The sequential expression of substrates to be exported, selective export, and a specific order of incorporation are some of the mechanisms that stand out to drive an efficient assembly process. In this work we analyze how the structural rod proteins, the scaffold protein FlgJ and the flagellar lytic enzyme SltF, interact in an orderly fashion to assemble the flagellar rod into the periplasmic space. A complex arrangement of transient interactions directs a dedicated flagellar muramidase towards the flagellar rod. All these interactions bring this protein to the proximity of the peptidoglycan wall while also modulating its enzymatic activity. This study suggests how a dynamic network of interactions participates in controlling SltF, a prominent component for flagellar formation.
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19
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Willcocks SJ, Denman C, Cia F, McCarthy E, Cuccui J, Wren BW. Virulence of the emerging pathogen, Burkholderia pseudomallei, depends upon the O-linked oligosaccharyltransferase, PglL. Future Microbiol 2021; 15:241-257. [PMID: 32271107 PMCID: PMC7611010 DOI: 10.2217/fmb-2019-0165] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Aim We sought to characterize the contribution of the O-OTase, PglL, to virulence in two Burkholderia spp. by comparing isogenic mutants in Burkholderia pseudomallei with the related species, Burkholderia thailandensis. Materials & methods We utilized an array of in vitro assays in addition to Galleria mellonella and murine in vivo models to assess virulence of the mutant and wild-type strains in each Burkholderia species. Results We found that pglL contributes to biofilm and twitching motility in both species. PglL uniquely affected morphology; cell invasion; intracellular motility; plaque formation and intergenus competition in B. pseudomallei. This mutant was attenuated in the murine model, and extended survival in a vaccine-challenge experiment. Conclusion Our data support a broad role for pglL in bacterial fitness and virulence, particularly in B. pseudomallei.
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Affiliation(s)
| | - Carmen Denman
- The London School of Hygiene & Tropical Medicine, WC1E 7HT, London, UK
| | - Felipe Cia
- The London School of Hygiene & Tropical Medicine, WC1E 7HT, London, UK
| | | | - Jon Cuccui
- The London School of Hygiene & Tropical Medicine, WC1E 7HT, London, UK
| | - Brendan W Wren
- The London School of Hygiene & Tropical Medicine, WC1E 7HT, London, UK
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20
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Nguyen VS, Spinelli S, Cascales É, Roussel A, Cambillau C, Leone P. Anchoring the T6SS to the cell wall: Crystal structure of the peptidoglycan binding domain of the TagL accessory protein. PLoS One 2021; 16:e0254232. [PMID: 34214145 PMCID: PMC8253398 DOI: 10.1371/journal.pone.0254232] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 06/22/2021] [Indexed: 11/22/2022] Open
Abstract
The type VI secretion system (T6SS) is a widespread mechanism of protein delivery into target cells, present in more than a quarter of all sequenced Gram-negative bacteria. The T6SS constitutes an important virulence factor, as it is responsible for targeting effectors in both prokaryotic and eukaryotic cells. The T6SS comprises a tail structure tethered to the cell envelope via a trans-envelope complex. In most T6SS, the membrane complex is anchored to the cell wall by the TagL accessory protein. In this study, we report the first crystal structure of a peptidoglycan-binding domain of TagL. The fold is conserved with members of the OmpA/Pal/MotB family, and more importantly, the peptidoglycan binding site is conserved. This structure further exemplifies how proteins involved in anchoring to the cell wall for different cellular functions rely on an interaction network with peptidoglycan strictly conserved.
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Affiliation(s)
- Van Son Nguyen
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, Marseille, France
- Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique (UMR7257), Marseille, France
| | - Silvia Spinelli
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, Marseille, France
- Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique (UMR7257), Marseille, France
| | - Éric Cascales
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Centre National de la Recherche Scientifique (UMR7255), Aix-Marseille Université, Marseille, France
| | - Alain Roussel
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, Marseille, France
- Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique (UMR7257), Marseille, France
| | - Christian Cambillau
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, Marseille, France
- Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique (UMR7257), Marseille, France
| | - Philippe Leone
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, Marseille, France
- Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique (UMR7257), Marseille, France
- * E-mail:
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21
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Kim YJ, Choi BJ, Park SH, Lee HB, Son JE, Choi U, Chi WJ, Lee CR. Distinct Amino Acid Availability-Dependent Regulatory Mechanisms of MepS and MepM Levels in Escherichia coli. Front Microbiol 2021; 12:677739. [PMID: 34276609 PMCID: PMC8278236 DOI: 10.3389/fmicb.2021.677739] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 05/28/2021] [Indexed: 12/17/2022] Open
Abstract
Peptidoglycan (PG) hydrolases play important roles in various aspects of bacterial physiology, including cytokinesis, PG synthesis, quality control of PG, PG recycling, and antibiotic resistance. However, the regulatory mechanisms of their expression are poorly understood. In this study, we have uncovered novel regulatory mechanisms of the protein levels of the synthetically lethal PG endopeptidases MepS and MepM, which are involved in PG synthesis. A mutant defective for both MepS and MepM was lethal in an amino acid-rich medium, whereas it exhibited almost normal growth in a minimal medium, suggesting the expendability of MepS and MepM in a minimal medium. Protein levels of MepS and MepM dramatically decreased in the minimal medium. Although MepM was revealed as a substrate of Prc, a periplasmic protease involved in the proteolysis of MepS, only the decrease in the MepS level in the minimal medium was affected by the prc depletion. Phenotypic and biochemical analyses showed that the presence of aromatic amino acids in the medium induced the accumulation of MepS, but not MepM, while the presence of glutamate increased the level of MepM, but not MepS. Together, these results demonstrate that the protein levels of the two major PG endopeptidases are regulated in an amino acid availability-dependent manner, but their molecular mechanisms and signaling are significantly distinct.
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Affiliation(s)
- Yung Jae Kim
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Byoung Jun Choi
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Si Hyoung Park
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Han Byeol Lee
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Ji Eun Son
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Umji Choi
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Won-Jae Chi
- Biological and Genetic Resource Assessment Division, National Institute of Biological Resource, Incheon, South Korea
| | - Chang-Ro Lee
- Department of Biological Sciences, Myongji University, Yongin, South Korea
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22
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Nakamura T, Shimizu T, Inagaki F, Okazaki S, Saha SS, Uda A, Watanabe K, Watarai M. Identification of Membrane-Bound Lytic Murein Transglycosylase A (MltA) as a Growth Factor for Francisella novicida in a Silkworm Infection Model. Front Cell Infect Microbiol 2021; 10:581864. [PMID: 33553001 PMCID: PMC7862118 DOI: 10.3389/fcimb.2020.581864] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 12/04/2020] [Indexed: 12/22/2022] Open
Abstract
Francisella tularensis, the causative agent of tularemia, is transmitted by arthropod vectors within mammalian hosts. The detailed mechanisms contributing to growth and survival of Francisella within arthropod remain poorly understood. To identify novel factors supporting growth and survival of Francisella within arthropods, a transposon mutant library of F. tularensis subsp. novicida (F. novicida) was screened using an F. novicida-silkworm infection model. Among 750 transposon mutants screened, the mltA-encoding membrane-bound lytic murein transglycosylase A (MltA) was identified as a novel growth factor of F. novicida in silkworms. Silkworms infection with an mltA deletion mutant (ΔmltA) resulted in a reduction in the number of bacteria and prolonged survival. The ΔmltA strain exhibited limited intracellular growth and cytotoxicity in BmN4 silkworm ovary cells. Moreover, the ΔmltA strain induced higher expression of the antimicrobial peptide in silkworms compared to the wild-type strain. These results suggest that F. novicida MltA contributes to the survival of F. novicida in silkworms via immune suppression-related mechanisms. Intracellular growth of the ΔmltA strain was also reduced in human monocyte THP-1 cells. These results also suggest the contribution of MltA to pathogenicity in humans and utility of the F. novicida-silkworm infection model to explore Francisella infection.
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Affiliation(s)
- Takemasa Nakamura
- Laboratory of Veterinary Public Health, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Takashi Shimizu
- Laboratory of Veterinary Public Health, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Fumiya Inagaki
- Laboratory of Veterinary Public Health, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Shoma Okazaki
- Laboratory of Veterinary Public Health, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Shib Shankar Saha
- Department of Pathology and Parasitology, Patuakhali Science and Technology University, Barisal, Bangladesh
| | - Akihiko Uda
- Department of Veterinary Science, National Institute of Infectious Diseases, Tokyo, Japan
| | - Kenta Watanabe
- Laboratory of Veterinary Public Health, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Masahisa Watarai
- Laboratory of Veterinary Public Health, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
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Ladant D. Bioengineering of Bordetella pertussis Adenylate Cyclase Toxin for Vaccine Development and Other Biotechnological Purposes. Toxins (Basel) 2021; 13:83. [PMID: 33499260 DOI: 10.3390/toxins13020083] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 01/14/2021] [Accepted: 01/15/2021] [Indexed: 12/15/2022] Open
Abstract
The adenylate cyclase toxin, CyaA, is one of the key virulent factors produced by Bordetella pertussis, the causative agent of whooping cough. This toxin primarily targets innate immunity to facilitate bacterial colonization of the respiratory tract. CyaA exhibits several remarkable characteristics that have been exploited for various applications in vaccinology and other biotechnological purposes. CyaA has been engineered as a potent vaccine vehicle to deliver antigens into antigen-presenting cells, while the adenylate cyclase catalytic domain has been used to design a robust genetic assay for monitoring protein-protein interactions in bacteria. These two biotechnological applications are briefly summarized in this chapter.
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Park SH, Kim YJ, Lee HB, Seok YJ, Lee CR. Genetic Evidence for Distinct Functions of Peptidoglycan Endopeptidases in Escherichia coli. Front Microbiol 2020; 11:565767. [PMID: 33013796 PMCID: PMC7516022 DOI: 10.3389/fmicb.2020.565767] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 08/17/2020] [Indexed: 02/01/2023] Open
Abstract
Peptidoglycan (PG) is an essential component of the bacterial exoskeleton that plays a pivotal role in the maintenance of cell shape and resistance to cell lysis under high turgor pressures. The synthesis and degradation of PG must be tightly regulated during bacterial cell elongation and division. Unlike enzymes involved in PG synthesis, PG hydrolases show high redundancy in many bacteria including Escherichia coli. In this study, we showed that PG endopeptidases have distinct roles in cell growth and division. Phenotypic analysis of mutants lacking one of seven PG endopeptidases identified a MepM-specific phenotype, salt sensitivity, and a MepS-specific phenotype, EDTA sensitivity. Complementation test in each phenotype showed that the phenotype of the mepM mutant was restored only by MepM, whereas the phenotype of the mepS mutant was restored by MepS or by overexpression of MepH, PbpG, or MepM. These distinct phenotypes depend on both the specific localizations and specific domains of MepM and MepS. Finally, using the identified phenotypes, we revealed that MepM and MepH were genetically associated with both penicillin-binding protein 1a (PBP1a) and PBP1b, whereas MepS and PbpG were genetically associated with only PBP1b. Notably, a defect in PBP1a or PBP1b phenocopied the mepM mutant, suggesting the importance of MepM on PG synthesis. Therefore, our results indicate that each PG endopeptidase plays a distinct role in cell growth and division, depending on its distinct domains and cellular localizations.
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Affiliation(s)
- Si Hyoung Park
- Department of Biological Sciences and Bioinformatics, Myongji University, Yongin, South Korea
| | - Yung Jae Kim
- Department of Biological Sciences and Bioinformatics, Myongji University, Yongin, South Korea
| | - Han Byeol Lee
- Department of Biological Sciences and Bioinformatics, Myongji University, Yongin, South Korea
| | - Yeong-Jae Seok
- Department of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul, South Korea
| | - Chang-Ro Lee
- Department of Biological Sciences and Bioinformatics, Myongji University, Yongin, South Korea
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Straume D, Piechowiak KW, Olsen S, Stamsås GA, Berg KH, Kjos M, Heggenhougen MV, Alcorlo M, Hermoso JA, Håvarstein LS. Class A PBPs have a distinct and unique role in the construction of the pneumococcal cell wall. Proc Natl Acad Sci U S A 2020; 117:6129-38. [PMID: 32123104 DOI: 10.1073/pnas.1917820117] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Peptidoglycan, the main structural component of the bacterial cell wall, is made of glycan strands cross-linked by short peptides. It has long been assumed that class A penicillin-binding proteins (PBPs) are the only enzymes capable of synthesizing glycan strands from lipid II. Recently, however, it was discovered that two non-PBP proteins, FtsW and RodA, constitute the core peptidoglycan polymerizing enzymes of the divisome and elongasome, respectively. What, then, is the role of class A PBPs in the construction of the bacterial cell wall? In contrast to previous assumptions, our results strongly suggest that class A PBPs are not an intrinsic part of the divisome and elongasome but have important autonomous roles in construction of the fully mature bacterial cell wall. In oval-shaped Streptococcus pneumoniae, septal and longitudinal peptidoglycan syntheses are performed by independent functional complexes: the divisome and the elongasome. Penicillin-binding proteins (PBPs) were long considered the key peptidoglycan-synthesizing enzymes in these complexes. Among these were the bifunctional class A PBPs, which are both glycosyltransferases and transpeptidases, and monofunctional class B PBPs with only transpeptidase activity. Recently, however, it was established that the monofunctional class B PBPs work together with transmembrane glycosyltransferases (FtsW and RodA) from the shape, elongation, division, and sporulation (SEDS) family to make up the core peptidoglycan-synthesizing machineries within the pneumococcal divisome (FtsW/PBP2x) and elongasome (RodA/PBP2b). The function of class A PBPs is therefore now an open question. Here we utilize the peptidoglycan hydrolase CbpD that targets the septum of S. pneumoniae cells to show that class A PBPs have an autonomous role during pneumococcal cell wall synthesis. Using assays to specifically inhibit the function of PBP2x and FtsW, we demonstrate that CbpD attacks nascent peptidoglycan synthesized by the divisome. Notably, class A PBPs could process this nascent peptidoglycan from a CbpD-sensitive to a CbpD-resistant form. The class A PBP-mediated processing was independent of divisome and elongasome activities. Class A PBPs thus constitute an autonomous functional entity which processes recently formed peptidoglycan synthesized by FtsW/PBP2×. Our results support a model in which mature pneumococcal peptidoglycan is synthesized by three functional entities, the divisome, the elongasome, and bifunctional PBPs. The latter modify existing peptidoglycan but are probably not involved in primary peptidoglycan synthesis.
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Abstract
The history of modern medicine cannot be written apart from the history of the antibiotics. Antibiotics are cytotoxic secondary metabolites that are isolated from Nature. The antibacterial antibiotics disproportionately target bacterial protein structure that is distinct from eukaryotic protein structure, notably within the ribosome and within the pathways for bacterial cell-wall biosynthesis (for which there is not a eukaryotic counterpart). This review focuses on a pre-eminent class of antibiotics-the β-lactams, exemplified by the penicillins and cephalosporins-from the perspective of the evolving mechanisms for bacterial resistance. The mechanism of action of the β-lactams is bacterial cell-wall destruction. In the monoderm (single membrane, Gram-positive staining) pathogen Staphylococcus aureus the dominant resistance mechanism is expression of a β-lactam-unreactive transpeptidase enzyme that functions in cell-wall construction. In the diderm (dual membrane, Gram-negative staining) pathogen Pseudomonas aeruginosa a dominant resistance mechanism (among several) is expression of a hydrolytic enzyme that destroys the critical β-lactam ring of the antibiotic. The key sensing mechanism used by P. aeruginosa is monitoring the molecular difference between cell-wall construction and cell-wall deconstruction. In both bacteria, the resistance pathways are manifested only when the bacteria detect the presence of β-lactams. This review summarizes how the β-lactams are sensed and how the resistance mechanisms are manifested, with the expectation that preventing these processes will be critical to future chemotherapeutic control of multidrug resistant bacteria.
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Affiliation(s)
- Jed F. Fisher
- Department of Chemistry and BiochemistryUniversity of Notre DameSouth BendIndiana
| | - Shahriar Mobashery
- Department of Chemistry and BiochemistryUniversity of Notre DameSouth BendIndiana
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27
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Abstract
The type VI secretion system (T6SS) is a multiprotein machine that uses a spring-like mechanism to inject effectors into target cells. The injection apparatus is composed of a baseplate on which is built a contractile tail tube/sheath complex. The inner tube, topped by the spike complex, is propelled outside of the cell by the contraction of the sheath. The injection system is anchored to the cell envelope and oriented towards the cell exterior by a trans-envelope complex. Effectors delivered by the T6SS are loaded within the inner tube or on the spike complex and can target prokaryotic and/or eukaryotic cells. Here we summarize the structure, assembly, and mechanism of action of the T6SS. We also review the function of effectors and their mode of recruitment and delivery.
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28
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Nakamura T, Shimizu T, Uda A, Watanabe K, Watarai M. Soluble lytic transglycosylase SLT of Francisella novicida is involved in intracellular growth and immune suppression. PLoS One 2019; 14:e0226778. [PMID: 31877174 PMCID: PMC6932806 DOI: 10.1371/journal.pone.0226778] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 12/03/2019] [Indexed: 12/12/2022] Open
Abstract
Francisella tularensis, a category-A bioterrorism agent causes tularemia. F. tularensis suppresses the immune response of host cells and intracellularly proliferates. However, the detailed mechanisms of immune suppression and intracellular growth are largely unknown. Here we developed a transposon mutant library to identify novel pathogenic factors of F. tularensis. Among 750 transposon mutants of F. tularensis subsp. novicida (F. novicida), 11 were isolated as less cytotoxic strains, and the genes responsible for cytotoxicity were identified. Among them, the function of slt, which encodes soluble lytic transglycosylase (SLT) was investigated in detail. An slt deletion mutant (Δslt) was less toxic to the human monocyte cell line THP-1 vs the wild-type strain. Although the wild-type strain proliferated in THP-1 cells, the number of intracellular Δslt mutant decreased in comparison. The Δslt mutant escaped from phagosomes during the early stages of infection, but the mutant was detected within the autophagosome, followed by degradation in lysosomes. Moreover, the Δslt mutant induced host cells to produce high levels of cytokines such as tumor necrosis factor-α, interleukin (IL)-6, and IL-1β, compared with the wild-type strain. These results suggest that the SLT of F. novicida is required for immune suppression and escape from autophagy to allow its survival in host cells.
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Affiliation(s)
- Takemasa Nakamura
- Joint Faculty of Veterinary Medicine, Laboratory of Veterinary Public Health, Yamaguchi University, Yamaguchi, Japan
| | - Takashi Shimizu
- Joint Faculty of Veterinary Medicine, Laboratory of Veterinary Public Health, Yamaguchi University, Yamaguchi, Japan
| | - Akihiko Uda
- Department of Veterinary Science, National Institute of Infectious Diseases, Shinjuku, Tokyo, Japan
| | - Kenta Watanabe
- Joint Faculty of Veterinary Medicine, Laboratory of Veterinary Public Health, Yamaguchi University, Yamaguchi, Japan
| | - Masahisa Watarai
- Joint Faculty of Veterinary Medicine, Laboratory of Veterinary Public Health, Yamaguchi University, Yamaguchi, Japan
- * E-mail:
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29
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Abstract
Bacteria need to deliver large molecules out of the cytosol to the extracellular space or even across membranes of neighboring cells to influence their environment, prevent predation, defeat competitors, or communicate. A variety of protein-secretion systems have evolved to make this process highly regulated and efficient. The type VI secretion system (T6SS) is one of the largest dynamic assemblies in gram-negative bacteria and allows for delivery of toxins into both bacterial and eukaryotic cells. The recent progress in structural biology and live-cell imaging shows the T6SS as a long contractile sheath assembled around a rigid tube with associated toxins anchored to a cell envelope by a baseplate and membrane complex. Rapid sheath contraction releases a large amount of energy used to push the tube and toxins through the membranes of neighboring target cells. Because reach of the T6SS is limited, some bacteria dynamically regulate its subcellular localization to precisely aim at their targets and thus increase efficiency of toxin translocation.
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Affiliation(s)
- Jing Wang
- Biozentrum, University of Basel, CH 4056 Basel, Switzerland
| | - Maj Brodmann
- Biozentrum, University of Basel, CH 4056 Basel, Switzerland
| | - Marek Basler
- Biozentrum, University of Basel, CH 4056 Basel, Switzerland
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30
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Sen R, Tagore S, De RK. Cluster Quality based Non-Reductional (CQNR) oversampling technique and effector protein predictor based on 3D structure (EPP3D) of proteins. Comput Biol Med 2019; 112:103374. [DOI: 10.1016/j.compbiomed.2019.103374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 07/26/2019] [Accepted: 07/26/2019] [Indexed: 11/28/2022]
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31
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Weaver AI, Jiménez-Ruiz V, Tallavajhala SR, Ransegnola BP, Wong KQ, Dörr T. Lytic transglycosylases RlpA and MltC assist in Vibrio cholerae daughter cell separation. Mol Microbiol 2019; 112:1100-1115. [PMID: 31286580 DOI: 10.1111/mmi.14349] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/04/2019] [Indexed: 12/21/2022]
Abstract
The cell wall is a crucial structural feature in the vast majority of bacteria and comprises a covalently closed network of peptidoglycan (PG) strands. While PG synthesis is important for survival under many conditions, the cell wall is also a dynamic structure, undergoing degradation and remodeling by 'autolysins', enzymes that break down PG. Cell division, for example, requires extensive PG remodeling, especially during separation of daughter cells, which depends heavily upon the activity of amidases. However, in Vibrio cholerae, we demonstrate that amidase activity alone is insufficient for daughter cell separation and that lytic transglycosylases RlpA and MltC both contribute to this process. MltC and RlpA both localize to the septum and are functionally redundant under normal laboratory conditions; however, only RlpA can support normal cell separation in low-salt media. The division-specific activity of lytic transglycosylases has implications for the local structure of septal PG, suggesting that there may be glycan bridges between daughter cells that cannot be resolved by amidases. We propose that lytic transglycosylases at the septum cleave PG strands that are crosslinked beyond the reach of the highly regulated activity of the amidase and clear PG debris that may block the completion of outer membrane invagination.
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Affiliation(s)
- Anna I Weaver
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, 14853, USA.,Department of Microbiology, Cornell University, Ithaca, NY, 14853, USA
| | - Valeria Jiménez-Ruiz
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Srikar R Tallavajhala
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Brett P Ransegnola
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Kimberly Q Wong
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Tobias Dörr
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, 14853, USA.,Department of Microbiology, Cornell University, Ithaca, NY, 14853, USA.,Cornell Institute of Host-Microbe Interactions and Disease, Cornell University, Ithaca, NY, 14853, USA
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32
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Abstract
Prediction of effector proteins is of paramount importance due to their crucial role as first-line invaders while establishing a pathogen-host interaction, often leading to infection of the host. Prediction of T6 effector proteins is a new challenge since the discovery of T6 Secretion System and the unique nature of the particular secretion system. In this paper, we have first designed a Python-based standalone tool, called PyPredT6, to predict T6 effector proteins. A total of 873 unique features has been extracted from the peptide and nucleotide sequences of the experimentally verified effector proteins. Based on these features and using machine learning algorithms, we have performed in silico prediction of T6 effector proteins in Vibrio cholerae and Yersinia pestis to establish the applicability of PyPredT6. PyPredT6 is available at http://projectphd.droppages.com/PyPredT6.html .
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Affiliation(s)
- Rishika Sen
- Machine Intelligence Unit, Indian Statistical Institute, 103 B.T. Road, Kolkata-700108, India
| | - Losiana Nayak
- Machine Intelligence Unit, Indian Statistical Institute, 103 B.T. Road, Kolkata-700108, India
| | - Rajat K. De
- Machine Intelligence Unit, Indian Statistical Institute, 103 B.T. Road, Kolkata-700108, India
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33
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Abstract
Bacterial contractile injection systems are fascinating particles that use a spring-like mechanism to inject an effector-loaded needle into target cells. A recent study shows that the intracellular bacterium Amoebophilus asiaticus uses arrays of contractile structures to escape from the amoeba phagosome.
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Affiliation(s)
- Eric Cascales
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, CNRS UMR7255, Aix-Marseille Université, Marseille Cedex 20, France.
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34
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Moynihan PJ, Cadby IT, Veerapen N, Jankute M, Crosatti M, Mukamolova GV, Lovering AL, Besra GS. The hydrolase LpqI primes mycobacterial peptidoglycan recycling. Nat Commun 2019; 10:2647. [PMID: 31201321 DOI: 10.1038/s41467-019-10586-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 05/14/2019] [Indexed: 12/26/2022] Open
Abstract
Growth and division by most bacteria requires remodelling and cleavage of their cell wall. A byproduct of this process is the generation of free peptidoglycan (PG) fragments known as muropeptides, which are recycled in many model organisms. Bacteria and hosts can harness the unique nature of muropeptides as a signal for cell wall damage and infection, respectively. Despite this critical role for muropeptides, it has long been thought that pathogenic mycobacteria such as Mycobacterium tuberculosis do not recycle their PG. Herein we show that M. tuberculosis and Mycobacterium bovis BCG are able to recycle components of their PG. We demonstrate that the core mycobacterial gene lpqI, encodes an authentic NagZ β-N-acetylglucosaminidase and that it is essential for PG-derived amino sugar recycling via an unusual pathway. Together these data provide a critical first step in understanding how mycobacteria recycle their peptidoglycan. Bacterial growth and division require remodelling of the cell wall, which generates free peptidoglycan fragments. Here, Moynihan et al. show that Mycobacterium tuberculosis can recycle components of their peptidoglycan, and characterise a crucial enzyme required for this process.
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35
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Lin L, Lezan E, Schmidt A, Basler M. Abundance of bacterial Type VI secretion system components measured by targeted proteomics. Nat Commun 2019; 10:2584. [PMID: 31197144 DOI: 10.1038/s41467-019-10466-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Accepted: 05/13/2019] [Indexed: 12/31/2022] Open
Abstract
The Type VI secretion system (T6SS) is important for bacterial competition as well as virulence in many Gram-negative bacteria and its dynamics and regulation varies significantly between species. To gain insights into the mechanisms regulating T6SS assembly, we apply targeted proteomics to determine the abundance of the key T6SS components in Vibrio cholerae, Pseudomonas aeruginosa and Acinetobacter baylyi. We show that while there are species specific exceptions, the abundance of most components is similar in all three bacteria and ranges from less than hundred to tens of thousands of copies per cell. The comparison of T6SS dynamics and protein abundance in V. cholerae grown under various conditions suggests that the critical component TssE and the secreted protein VasX are unstable and this diminishes T6SS assembly when protein synthesis is limited. Our quantitative analysis opens possibilities to build realistic models of T6SS assembly and to identify principles of T6SS regulation in various species. Type VI secretion systems (T6SS) are important for bacterial interaction, competition and virulence, but the abundance and assembly of their components is still not well understood. Here, the authors apply targeted proteomics to measure the abundance of T6SS components across different species and conditions.
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36
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Santin YG, Camy CE, Zoued A, Doan T, Aschtgen MS, Cascales E. Role and Recruitment of the TagL Peptidoglycan-Binding Protein during Type VI Secretion System Biogenesis. J Bacteriol 2019; 201:e00173-19. [PMID: 30910811 DOI: 10.1128/JB.00173-19] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 03/19/2019] [Indexed: 12/29/2022] Open
Abstract
The type VI secretion system (T6SS) is an injection apparatus that uses a springlike mechanism for effector delivery. The contractile tail is composed of a needle tipped by a sharpened spike and wrapped by the sheath that polymerizes in an extended conformation on the assembly platform, or baseplate. Contraction of the sheath propels the needle and effectors associated with it into target cells. The passage of the needle through the cell envelope of the attacker is ensured by a dedicated trans-envelope channel complex. This membrane complex (MC) comprises the TssJ lipoprotein and the TssL and TssM inner membrane proteins. MC assembly is a hierarchized mechanism in which the different subunits are recruited in a specific order: TssJ, TssM, and then TssL. Once assembled, the MC serves as a docking station for the baseplate. In enteroaggregative Escherichia coli, the MC is accessorized by TagL, a peptidoglycan-binding (PGB) inner membrane-anchored protein. Here, we show that the PGB domain is the only functional domain of TagL and that the N-terminal transmembrane region mediates contact with the TssL transmembrane helix. Finally, we conduct fluorescence microscopy experiments to position TagL in the T6SS biogenesis pathway, demonstrating that TagL is recruited to the membrane complex downstream of TssL and is not required for baseplate docking.IMPORTANCE Bacteria use weapons to deliver effectors into target cells. One of these weapons, called the type VI secretion system (T6SS), could be compared to a nano-spear gun using a springlike mechanism for effector injection. By targeting bacteria and eukaryotic cells, the T6SS reshapes bacterial communities and hijacks host cell defenses. In enteroaggregative Escherichia coli, the T6SS is a multiprotein machine that comprises a cytoplasmic tail and a peptidoglycan-anchored trans-envelope channel. In this work, we show that TagL comprises an N-terminal domain that mediates contact with the channel and a peptidoglycan-binding domain that binds the cell wall. We then determine at which stage of T6SS biogenesis TagL is recruited and how TagL absence impacts the assembly pathway.
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Affiliation(s)
- Sarah Coulthurst
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
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38
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Abstract
The Type VI secretion system (T6SS) is a protein nanomachine that is widespread in Gram-negative bacteria and is used to translocate effector proteins directly into neighbouring cells. It represents a versatile bacterial weapon that can deliver effectors into distinct classes of target cells, playing key roles in inter-bacterial competition and bacterial interactions with eukaryotic cells. This versatility is underpinned by the ability of the T6SS to deliver a vast array of effector proteins, with many distinct activities and modes of interaction with the secretion machinery. Recent work has highlighted the importance and diversity of interactions mediated by T6SSs within polymicrobial communities, and offers new molecular insights into effector delivery and action in target cells.
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Affiliation(s)
- Sarah Coulthurst
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
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39
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Irazoki O, Hernandez SB, Cava F. Peptidoglycan Muropeptides: Release, Perception, and Functions as Signaling Molecules. Front Microbiol 2019; 10:500. [PMID: 30984120 PMCID: PMC6448482 DOI: 10.3389/fmicb.2019.00500] [Citation(s) in RCA: 106] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 02/27/2019] [Indexed: 12/12/2022] Open
Abstract
Peptidoglycan (PG) is an essential molecule for the survival of bacteria, and thus, its biosynthesis and remodeling have always been in the spotlight when it comes to the development of antibiotics. The peptidoglycan polymer provides a protective function in bacteria, but at the same time is continuously subjected to editing activities that in some cases lead to the release of peptidoglycan fragments (i.e., muropeptides) to the environment. Several soluble muropeptides have been reported to work as signaling molecules. In this review, we summarize the mechanisms involved in muropeptide release (PG breakdown and PG recycling) and describe the known PG-receptor proteins responsible for PG sensing. Furthermore, we overview the role of muropeptides as signaling molecules, focusing on the microbial responses and their functions in the host beyond their immunostimulatory activity.
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Affiliation(s)
- Oihane Irazoki
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
| | - Sara B Hernandez
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
| | - Felipe Cava
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
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40
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De Meyer F, Danneels B, Acar T, Rasolomampianina R, Rajaonah MT, Jeannoda V, Carlier A. Adaptations and evolution of a heritable leaf nodule symbiosis between Dioscorea sansibarensis and Orrella dioscoreae. ISME J 2019; 13:1831-44. [PMID: 30877285 DOI: 10.1038/s41396-019-0398-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 03/05/2019] [Accepted: 03/05/2019] [Indexed: 12/31/2022]
Abstract
Various plant species establish intimate symbioses with bacteria within their aerial organs. The bacteria are contained within nodules or glands often present in distinctive patterns on the leaves in what is commonly referred to as leaf nodule symbiosis. We describe here a highly specific symbiosis between a wild yam species from Madagascar, Dioscorea sansibarensis and bacteria of the species Orrella dioscoreae. Using whole-genome sequencing of plastids and bacteria from wild-collected samples, we show phylogenetic patterns consistent with a dominant vertical mode of transmission of the symbionts. Unique so far among leaf nodule symbioses, the bacteria can be cultured and are amenable to comparative transcriptomics, revealing a potential role in complementing the host's arsenal of secondary metabolites. We propose a recent establishment of a vertical mode of transmission in this symbiosis which, together with a large effective population size explains the cultivability and apparent lack of genome reductive evolution in O. dioscoreae. We leverage these unique features to reveal pathways and functions under positive selection in these specialized endophytes, highlighting the candidate mechanisms enabling a permanent association in the phyllosphere.
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41
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Abstract
The type III secretion system (T3SS) is one of the largest transmembrane complexes in bacteria, comprising several intricately linked and embedded substructures. The assembly of this nanomachine is a hierarchical process which is regulated and controlled by internal and external cues at several critical points. Recently, it has become obvious that the assembly of the T3SS is not a unidirectional and deterministic process, but that parts of the T3SS constantly exchange or rearrange. This article aims to give an overview on the assembly and post-assembly dynamics of the T3SS, with a focus on emerging general concepts and adaptations of the general assembly pathway.
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Affiliation(s)
- Andreas Diepold
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Straße 10, 35043, Marburg, Germany.
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Oliveira ACP, Ferreira RM, Ferro MIT, Ferro JA, Chandler M, Varani AM. Transposons and pathogenicity in Xanthomonas: acquisition of murein lytic transglycosylases by Tn Xax1 enhances Xanthomonas citri subsp. citri 306 virulence and fitness. PeerJ 2018; 6:e6111. [PMID: 30588403 PMCID: PMC6304161 DOI: 10.7717/peerj.6111] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2018] [Accepted: 11/12/2018] [Indexed: 01/10/2023] Open
Abstract
Xanthomonas citri subsp. citri 306 (XccA) is the causal agent of type A citrus canker (CC), one of the most significant citriculture diseases. Murein lytic transglycosylases (LT), potentially involved in XccA pathogenicity, are enzymes responsible for peptidoglycan structure assembly, remodeling and degradation. They directly impact cell wall expansion during bacterial growth, septum division allowing cell separation, cell wall remodeling allowing flagellar assembly, bacterial conjugation, muropeptide recycling, and secretion system assembly, in particular the Type 3 Secretion System involved in bacterial virulence, which play a fundamental role in XccA pathogenicity. Information about the XccA LT arsenal is patchy: little is known about family diversity, their exact role or their connection to virulence in this bacterium. Among the LTs with possible involvement in virulence, two paralogue open reading frames (ORFs) (one on the chromosome and one in plasmid pXAC64) are passenger genes of the Tn3 family transposon TnXax1, known to play a significant role in the evolution and emergence of pathogenicity in Xanthomonadales and to carry a variety of virulence determinants. This study addresses LT diversity in the XccA genome and examines the role of plasmid and chromosomal TnXax1 LT passenger genes using site-directed deletion mutagenesis and functional characterization. We identified 13 XccA LTs: 12 belong to families 1A, 1B, 1C, 1D (two copies), 1F, 1G, 3A, 3B (two copies), 5A, 6A and one which is non-categorized. The non-categorized LT is exclusive to the Xanthomonas genus and related to the 3B family but contains an additional domain linked to carbohydrate metabolism. The categorized LTs are probably involved in cell wall remodeling to allow insertion of type 3, 4 and 6 secretion systems, flagellum assembly, division and recycling of cell wall and degradation and control of peptidoglycan production. The TnXax1 passenger LT genes (3B family) are not essential to XccA or for CC development but are implicated in peptidoglycan metabolism, directly impacting bacterial fitness and CC symptom enhancement in susceptible hosts (e.g., Citrus sinensis). This underlines the role of TnXax1 as a virulence and pathogenicity-propagating agent in XccA and suggests that LT acquisition by horizontal gene transfer mediated by TnXax1 may improve bacterial fitness, conferring adaptive advantages to the plant-pathogen interaction process.
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Affiliation(s)
- Amanda C P Oliveira
- School of Agricultural and Veterinarian Sciences-Agricultural and Livestock Microbiology Graduation Program, Universidade Estadual Paulista, Jaboticabal, Sao Paulo, Brazil
| | - Rafael M Ferreira
- School of Agricultural and Veterinarian Sciences, Universidade Estadual Paulista, Jaboticabal, Sao Paulo, Brazil
| | - Maria Inês T Ferro
- School of Agricultural and Veterinarian Sciences, Universidade Estadual Paulista, Jaboticabal, Sao Paulo, Brazil
| | - Jesus A Ferro
- School of Agricultural and Veterinarian Sciences, Universidade Estadual Paulista, Jaboticabal, Sao Paulo, Brazil
| | - Mick Chandler
- Department of Biochemistry, Georgetown University, WA, USA
| | - Alessandro M Varani
- School of Agricultural and Veterinarian Sciences, Universidade Estadual Paulista, Jaboticabal, Sao Paulo, Brazil
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Abstract
The clinical and epidemiological threat of the growing antimicrobial resistance in Gram-negative pathogens, particularly for β-lactams, the most frequently used and relevant antibiotics, urges research to find new therapeutic weapons to combat the infections caused by these microorganisms. An essential previous step in the development of these therapeutic solutions is to identify their potential targets in the biology of the pathogen. This is precisely what we sought to do in this review specifically regarding the barely exploited field analyzing the interplay among the biology of the peptidoglycan and related processes, such as β-lactamase regulation and virulence. Hence, here we gather, analyze, and integrate the knowledge derived from published works that provide information on the topic, starting with those dealing with the historically neglected essential role of the Gram-negative peptidoglycan in virulence, including structural, biogenesis, remodeling, and recycling aspects, in addition to proinflammatory and other interactions with the host. We also review the complex link between intrinsic β-lactamase production and peptidoglycan metabolism, as well as the biological costs potentially associated with the expression of horizontally acquired β-lactamases. Finally, we analyze the existing evidence from multiple perspectives to provide useful clues for identifying targets enabling the future development of therapeutic options attacking the peptidoglycan-virulence interconnection as a key weak point of the Gram-negative pathogens to be used, if not to kill the bacteria, to mitigate their capacity to produce severe infections.
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Affiliation(s)
- Carlos Juan
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases, Instituto de Investigación Sanitaria de Baleares (IdISBa), Palma, Spain
| | - Gabriel Torrens
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases, Instituto de Investigación Sanitaria de Baleares (IdISBa), Palma, Spain
| | - Isabel Maria Barceló
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases, Instituto de Investigación Sanitaria de Baleares (IdISBa), Palma, Spain
| | - Antonio Oliver
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases, Instituto de Investigación Sanitaria de Baleares (IdISBa), Palma, Spain
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Dik DA, Batuecas MT, Lee M, Mahasenan KV, Marous DR, Lastochkin E, Fisher JF, Hermoso JA, Mobashery S. A Structural Dissection of the Active Site of the Lytic Transglycosylase MltE from Escherichia coli. Biochemistry 2018; 57:6090-6098. [PMID: 30256085 DOI: 10.1021/acs.biochem.8b00800] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Lytic transglycosylases (LTs) are bacterial enzymes that catalyze the cleavage of the glycan strands of the bacterial cell wall. The mechanism of this cleavage is a remarkable intramolecular transacetalization reaction, accomplished by an ensemble of active-site residues. Because the LT reaction occurs in parallel with the cell wall bond-forming reactions catalyzed by the penicillin-binding proteins, simultaneous inhibition of both enzymes can be particularly bactericidal to Gram-negative bacteria. The MltE lytic transglycosylase is the smallest of the eight LTs encoded by the Escherichia coli genome. Prior crystallographic and computational studies identified four active-site residues-E64, S73, S75, and Y192-as playing roles in catalysis. Each of these four residues was individually altered by mutation to give four variant enzymes (E64Q, S73A, S75A, and Y192F). All four variants showed reduced catalytic activity [soluble wild type (100%) > soluble Y192F and S75A (both 40%) > S73A (4%) > E64Q (≤1%)]. The crystal structure of each variant protein was determined at the resolution of 2.12 Å for E64Q, 2.33 Å for Y192F, 1.38 Å for S73A, and 1.35 Å for S75A. These variants show alteration of the hydrogen-bond interactions of the active site. Within the framework of a prior computational study of the LT mechanism, we suggest the mechanistic role of these four active-site residues in MltE catalysis.
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Affiliation(s)
- David A Dik
- Department of Chemistry and Biochemistry , University of Notre Dame , 352 McCourtney Hall , Notre Dame , Indiana 46556 , United States
| | - María T Batuecas
- Department of Crystallography and Structural Biology , Inst. Química-Física "Rocasolano", CSIC , Serrano 119 , 28006 Madrid , Spain
| | - Mijoon Lee
- Department of Chemistry and Biochemistry , University of Notre Dame , 352 McCourtney Hall , Notre Dame , Indiana 46556 , United States
| | - Kiran V Mahasenan
- Department of Chemistry and Biochemistry , University of Notre Dame , 352 McCourtney Hall , Notre Dame , Indiana 46556 , United States
| | - Daniel R Marous
- Department of Chemistry and Biochemistry , University of Notre Dame , 352 McCourtney Hall , Notre Dame , Indiana 46556 , United States
| | - Elena Lastochkin
- Department of Chemistry and Biochemistry , University of Notre Dame , 352 McCourtney Hall , Notre Dame , Indiana 46556 , United States
| | - Jed F Fisher
- Department of Chemistry and Biochemistry , University of Notre Dame , 352 McCourtney Hall , Notre Dame , Indiana 46556 , United States
| | - Juan A Hermoso
- Department of Crystallography and Structural Biology , Inst. Química-Física "Rocasolano", CSIC , Serrano 119 , 28006 Madrid , Spain
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry , University of Notre Dame , 352 McCourtney Hall , Notre Dame , Indiana 46556 , United States
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Santin YG, Doan T, Lebrun R, Espinosa L, Journet L, Cascales E. In vivo TssA proximity labelling during type VI secretion biogenesis reveals TagA as a protein that stops and holds the sheath. Nat Microbiol 2018; 3:1304-13. [DOI: 10.1038/s41564-018-0234-3] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 07/31/2018] [Indexed: 12/14/2022]
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Crépin S, Ottosen EN, Peters K, Smith SN, Himpsl SD, Vollmer W, Mobley HLT. The lytic transglycosylase MltB connects membrane homeostasis and in vivo fitness of Acinetobacter baumannii. Mol Microbiol 2018; 109:745-762. [PMID: 29884996 PMCID: PMC6185781 DOI: 10.1111/mmi.14000] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 05/30/2018] [Accepted: 07/15/2018] [Indexed: 01/06/2023]
Abstract
Acinetobacter baumannii has emerged as a leading nosocomial pathogen, infecting a wide range of anatomic sites including the respiratory tract and the bloodstream. In addition to being multi‐drug resistant, little is known about the molecular basis of A. baumannii pathogenesis. To better understand A. baumannii virulence, a combination of a transposon‐sequencing (TraDIS) screen and the neutropenic mouse model of bacteremia was used to identify the full set of fitness genes required during bloodstream infection. The lytic transglycosylase MltB was identified as a critical fitness factor. MltB cleaves the MurNAc‐GlcNAc bond of peptidoglycan, which leads to cell wall remodeling. Here we show that MltB is part of a complex network connecting resistance to stresses, membrane homeostasis, biogenesis of pili and in vivo fitness. Indeed, inactivation of mltB not only impaired resistance to serum complement, cationic antimicrobial peptides and oxygen species, but also altered the cell envelope integrity, activated the envelope stress response, drastically reduced the number of pili at the cell surface and finally, significantly decreased colonization of both the bloodstream and the respiratory tract.
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Affiliation(s)
- Sébastien Crépin
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Elizabeth N Ottosen
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Katharina Peters
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, UK
| | - Sara N Smith
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Stephanie D Himpsl
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Waldemar Vollmer
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, UK
| | - Harry L T Mobley
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
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García-Ramos M, de la Mora J, Ballado T, Camarena L, Dreyfus G. Biochemical and Phylogenetic Study of SltF, a Flagellar Lytic Transglycosylase from Rhodobacter sphaeroides. J Bacteriol 2018; 200:e00397-18. [PMID: 30061356 DOI: 10.1128/JB.00397-18] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 07/27/2018] [Indexed: 11/20/2022] Open
Abstract
In this work, we have characterized the soluble lytic transglycosylase (SltF) from Rhodobacter sphaeroides that interacts with the scaffolding protein FlgJ in the periplasm to open space at the cell wall peptidoglycan heteropolymer for the emerging rod. The characterization of the genetic context of flgJ and sltF in alphaproteobacteria shows that these two separate genes coexist frequently in a flagellar gene cluster. Two domains of unknown function in SltF were studied, and the results show that the deletion of a 17-amino-acid segment near the N terminus does not show a recognizable phenotype, whereas the deletion of 47 and 95 amino acids of the C terminus of SltF disrupts the interaction with FlgJ without affecting the transglycosylase catalytic activity of SltF. These mutant proteins are unable to support swimming, indicating that the physical interaction between SltF and FlgJ is central for flagellar formation. In a maximum likelihood tree of representative lytic transglycosylases, all of the flagellar SltF proteins cluster in subfamily 1F. From this analysis, it was also revealed that the lytic transglycosylases related to the type III secretion systems present in pathogens cluster with the closely related flagellar transglycosylases.IMPORTANCE Flagellar biogenesis is a highly orchestrated event where the flagellar structure spans the bacterial cell envelope. The rod diameter of approximately 4 nm is larger than the estimated pore size of the peptidoglycan layer; hence, its insertion requires the localized and controlled lysis of the cell wall. We found that a 47-residue domain of the C terminus of the lytic transglycosylase (LT) SltF of R. sphaeroides is involved in the recognition of the rod chaperone FlgJ. We also found that in many alphaproteobacteria, the flagellar cluster includes a homolog of SltF and FlgJ, indicating that association of an LT with the flagellar machinery is ancestral. A maximum likelihood tree shows that family 1 of LTs segregates into seven subfamilies.
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Abstract
The importance of the cell wall to the viability of the bacterium is underscored by the breadth of antibiotic structures that act by blocking key enzymes that are tasked with cell-wall creation, preservation, and regulation. The interplay between cell-wall integrity, and the summoning forth of resistance mechanisms to deactivate cell-wall-targeting antibiotics, involves exquisite orchestration among cell-wall synthesis and remodeling and the detection of and response to the antibiotics through modulation of gene regulation by specific effectors. Given the profound importance of antibiotics to the practice of medicine, the assertion that understanding this interplay is among the most fundamentally important questions in bacterial physiology is credible. The enigmatic regulation of the expression of the AmpC β-lactamase, a clinically significant and highly regulated resistance response of certain Gram-negative bacteria to the β-lactam antibiotics, is the exemplar of this challenge. This review gives a current perspective to this compelling, and still not fully solved, 35-year enigma.
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Affiliation(s)
- David A. Dik
- Department of Chemistry and Biochemistry, McCourtney Hall, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Jed F. Fisher
- Department of Chemistry and Biochemistry, McCourtney Hall, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry, McCourtney Hall, University of Notre Dame, Notre Dame, Indiana 46556, United States
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Abstract
Francisella tularensisis subsp. tularensis is an intracellular bacterial pathogen and the causative agent of the life-threatening zoonotic disease tularemia. The Francisella Pathogenicity Island encodes a large secretion apparatus, known as a Type VI Secretion System (T6SS), which is essential for Francisella to escape from its phagosome and multiply within host macrophages and to cause disease in animals. The T6SS, found in one-quarter of Gram-negative bacteria including many highly pathogenic ones, is a recently discovered secretion system that is not yet fully understood. Nevertheless, there have been remarkable advances in our understanding of the structure, composition, and function of T6SSs of several bacteria in the past few years. The system operates like an inside-out headless contractile phage that is anchored to the bacterial membrane via a baseplate and membrane complex. The system injects effector molecules across the inner and outer bacterial membrane and into host prokaryotic or eukaryotic targets to kill, intoxicate, or in the case of Francisella, hijack the target cell. Recent advances include an atomic model of the contractile sheath, insights into the mechanics of sheath contraction, the composition of the baseplate and membrane complex, the process of assembly of the apparatus, and identification of numerous effector molecules and activities. While Francisella T6SS appears to be an outlier among T6SSs, with limited or no sequence homology with other systems, its structure and organization are strikingly similar to other systems. Nevertheless, we have only scratched the surface in uncovering the mysteries of the Francisella T6SS, and there are numerous questions that remain to be answered.
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Affiliation(s)
- Daniel L. Clemens
- Division of Infectious Diseases, Department of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | | | - Marcus A. Horwitz
- Division of Infectious Diseases, Department of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
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Byun B, Mahasenan KV, Dik DA, Marous DR, Speri E, Kumarasiri M, Fisher JF, Hermoso JA, Mobashery S. Mechanism of the Escherichia coli MltE lytic transglycosylase, the cell-wall-penetrating enzyme for Type VI secretion system assembly. Sci Rep 2018; 8:4110. [PMID: 29515200 DOI: 10.1038/s41598-018-22527-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Lytic transglycosylases (LTs) catalyze the non-hydrolytic cleavage of the bacterial cell wall by an intramolecular transacetalization reaction. This reaction is critically and broadly important in modifications of the bacterial cell wall in the course of its biosynthesis, recycling, manifestation of virulence, insertion of structural entities such as the flagellum and the pili, among others. The first QM/MM analysis of the mechanism of reaction of an LT, that for the Escherichia coli MltE, is undertaken. The study reveals a conformational itinerary consistent with an oxocarbenium-like transition state, characterized by a pivotal role for the active-site glutamic acid in proton transfer. Notably, an oxazolinium intermediate, as a potential intermediate, is absent. Rather, substrate-assisted catalysis is observed through a favorable dipole provided by the N-acetyl carbonyl group of MurNAc saccharide. This interaction stabilizes the incipient positive charge development in the transition state. This mechanism coincides with near-synchronous acetal cleavage and acetal formation.
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