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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] [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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2
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Gerstmans H, Duyvejonck L, Vázquez R, Staes I, Borloo J, Abdelkader K, Leroy J, Cremelie E, Gutiérrez D, Tamés-Caunedo H, Ruas-Madiedo P, Rodríguez A, Aertsen A, Lammertyn J, Lavigne R, Briers Y. Distinct mode of action of a highly stable, engineered phage lysin killing Gram-negative bacteria. Microbiol Spectr 2023; 11:e0181323. [PMID: 37971248 PMCID: PMC10714810 DOI: 10.1128/spectrum.01813-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 10/12/2023] [Indexed: 11/19/2023] Open
Abstract
IMPORTANCE Engineered lysins are considered as highly promising alternatives for antibiotics. Our previous screening study using VersaTile technology identified 1D10 as a possible lead compound with activity against Acinetobacter baumannii strains under elevated human serum concentrations. In this manuscript, we reveal an unexpected mode of action and exceptional thermoresistance for lysin 1D10. Our findings shed new light on the development of engineered lysins, providing valuable insights for future research in this field.
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Affiliation(s)
- Hans Gerstmans
- Department of Biotechnology, Ghent University, Ghent, Belgium
- Department of Biosystems, KU Leuven, Leuven, Belgium
| | - Lisa Duyvejonck
- Department of Biotechnology, Ghent University, Ghent, Belgium
| | - Roberto Vázquez
- Department of Biotechnology, Ghent University, Ghent, Belgium
| | - Ines Staes
- Department of Microbial and Molecular Systems, Leuven, Belgium
| | | | - Karim Abdelkader
- Department of Biotechnology, Ghent University, Ghent, Belgium
- Department of Microbiology and Immunology, Beni-Suef University, Beni-Suef, Egypt
| | - Jeroen Leroy
- Department of Biotechnology, Ghent University, Ghent, Belgium
| | - Emma Cremelie
- Department of Biotechnology, Ghent University, Ghent, Belgium
| | - Diana Gutiérrez
- Department of Biotechnology, Ghent University, Ghent, Belgium
| | - Héctor Tamés-Caunedo
- Dairy Research Institute of Asturias, Spanish National Research Council (IPLA-CSIC), Villaviciosa, Asturias, Spain
| | - Patricia Ruas-Madiedo
- Dairy Research Institute of Asturias, Spanish National Research Council (IPLA-CSIC), Villaviciosa, Asturias, Spain
| | - Ana Rodríguez
- Dairy Research Institute of Asturias, Spanish National Research Council (IPLA-CSIC), Villaviciosa, Asturias, Spain
| | - Abram Aertsen
- Department of Microbial and Molecular Systems, Leuven, Belgium
| | | | - Rob Lavigne
- Department of Biosystems, KU Leuven, Leuven, Belgium
| | - Yves Briers
- Department of Biotechnology, Ghent University, Ghent, Belgium
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3
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Allsopp LP, Bernal P. Killing in the name of: T6SS structure and effector diversity. MICROBIOLOGY (READING, ENGLAND) 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] [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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4
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Heterologous Assembly of the Type VI Secretion System Empowers Laboratory Escherichia coli with Antimicrobial and Cell Penetration Capabilities. Appl Environ Microbiol 2022; 88:e0130522. [PMID: 36154120 DOI: 10.1128/aem.01305-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] 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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5
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de Oliveira ACP, Ferreira RM, Ferro MIT, Ferro JA, Zamuner C, Ferreira H, Varani AM. XAC4296 Is a Multifunctional and Exclusive Xanthomonadaceae Gene Containing a Fusion of Lytic Transglycosylase and Epimerase Domains. Microorganisms 2022; 10:microorganisms10051008. [PMID: 35630451 PMCID: PMC9143381 DOI: 10.3390/microorganisms10051008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 04/29/2022] [Accepted: 05/09/2022] [Indexed: 02/05/2023] Open
Abstract
Microorganisms have a limited and highly adaptable repertoire of genes capable of encoding proteins containing single or variable multidomains. The phytopathogenic bacteria Xanthomonas citri subsp. citri (X. citri) (Xanthomonadaceae family), the etiological agent of Citrus Canker (CC), presents a collection of multidomain and multifunctional enzymes (MFEs) that remains to be explored. Recent studies have shown that multidomain enzymes that act on the metabolism of the peptidoglycan and bacterial cell wall, belonging to the Lytic Transglycosylases (LTs) superfamily, play an essential role in X. citri biology. One of these LTs, named XAC4296, apart from the Transglycosylase SLT_2 and Peptidoglycan binding-like domains, contains an unexpected aldose 1-epimerase domain linked to the central metabolism; therefore, resembling a canonical MFE. In this work, we experimentally characterized XAC4296 revealing its role as an MFE and demonstrating its probable gene fusion origin and evolutionary history. The XAC4296 is expressed during plant-pathogen interaction, and the Δ4296 mutant impacts CC progression. Moreover, Δ4296 exhibited chromosome segregation and cell division errors, and sensitivity to ampicillin, suggesting not only LT activity but also that the XAC4296 may also contribute to resistance to β-lactams. However, both Δ4296 phenotypes can be restored when the mutant is supplemented with sucrose or glutamic acid as a carbon and nitrogen source, respectively; therefore, supporting the epimerase domain’s functional relationship with the central carbon and cell wall metabolism. Taken together, these results elucidate the role of XAC4296 as an MFE in X. citri, also bringing new insights into the evolution of multidomain proteins and antimicrobial resistance in the Xanthomonadaceae family.
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Affiliation(s)
- Amanda C. P. de Oliveira
- Graduate Program in Agricultural and Livestock Microbiology, School of Agricultural and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal 14884-900, SP, Brazil;
- Department of Agricultural and Environmental Biotechnology, School of Agricultural and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal 14884-900, SP, Brazil; (R.M.F.); (M.I.T.F.); (J.A.F.)
| | - Rafael M. Ferreira
- Department of Agricultural and Environmental Biotechnology, School of Agricultural and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal 14884-900, SP, Brazil; (R.M.F.); (M.I.T.F.); (J.A.F.)
- Graduate Program in Genetics and Plant Breeding, School of Agricultural and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal 14884-900, SP, Brazil
| | - Maria Inês T. Ferro
- Department of Agricultural and Environmental Biotechnology, School of Agricultural and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal 14884-900, SP, Brazil; (R.M.F.); (M.I.T.F.); (J.A.F.)
| | - Jesus A. Ferro
- Department of Agricultural and Environmental Biotechnology, School of Agricultural and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal 14884-900, SP, Brazil; (R.M.F.); (M.I.T.F.); (J.A.F.)
| | - Caio Zamuner
- Department of General and Applied Biology, Institute of Biosciences, São Paulo State University (UNESP), Rio Claro 13506-900, SP, Brazil; (C.Z.); (H.F.)
| | - Henrique Ferreira
- Department of General and Applied Biology, Institute of Biosciences, São Paulo State University (UNESP), Rio Claro 13506-900, SP, Brazil; (C.Z.); (H.F.)
| | - Alessandro M. Varani
- Department of Agricultural and Environmental Biotechnology, School of Agricultural and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal 14884-900, SP, Brazil; (R.M.F.); (M.I.T.F.); (J.A.F.)
- Correspondence:
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6
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Smith TE, Li Y, Perreau J, Moran NA. Elucidation of host and symbiont contributions to peptidoglycan metabolism based on comparative genomics of eight aphid subfamilies and their Buchnera. PLoS Genet 2022; 18:e1010195. [PMID: 35522718 PMCID: PMC9116674 DOI: 10.1371/journal.pgen.1010195] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 05/18/2022] [Accepted: 04/09/2022] [Indexed: 11/23/2022] Open
Abstract
Pea aphids (Acyrthosiphon pisum) are insects containing genes of bacterial origin with putative functions in peptidoglycan (PGN) metabolism. Of these, rlpA1-5, amiD, and ldcA are highly expressed in bacteriocytes, specialized aphid cells that harbor the obligate bacterial symbiont Buchnera aphidicola, required for amino acid supplementation of the host's nutrient-poor diet. Despite genome reduction associated with endosymbiosis, pea aphid Buchnera retains genes for the synthesis of PGN while Buchnera of many other aphid species partially or completely lack these genes. To explore the evolution of aphid horizontally-transferred genes (HTGs) and to elucidate how host and symbiont genes contribute to PGN production, we sequenced genomes from four deeply branching lineages, such that paired aphid and Buchnera genomes are now available for 17 species representing eight subfamilies. We identified all host and symbiont genes putatively involved in PGN metabolism. Phylogenetic analyses indicate that each HTG family was present in the aphid shared ancestor, but that each underwent a unique pattern of gene loss or duplication in descendant lineages. While four aphid rlpA gene subfamilies show no relation to symbiont PGN gene repertoire, the loss of aphid amiD and ldcA HTGs coincides with the loss of symbiont PGN metabolism genes. In particular, the coincident loss of host amiD and symbiont murCEF in tribe Aphidini, in contrast to tribe Macrosiphini, suggests either 1) functional linkage between these host and symbiont genes, or 2) Aphidini has lost functional PGN synthesis and other retained PGN pathway genes are non-functional. To test these hypotheses experimentally, we used cell-wall labeling methods involving a d-alanine probe and found that both Macrosiphini and Aphidini retain Buchnera PGN synthesis. Our results imply that compensatory adaptations can preserve PGN synthesis despite the loss of some genes considered essential for this pathway, highlighting the importance of the cell wall in these symbioses.
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Affiliation(s)
- Thomas E. Smith
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas, United States of America
| | - Yiyuan Li
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas, United States of America
| | - Julie Perreau
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas, United States of America
| | - Nancy A. Moran
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas, United States of America
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7
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Sireci G, Badami GD, Di Liberto D, Blanda V, Grippi F, Di Paola L, Guercio A, de la Fuente J, Torina A. Recent Advances on the Innate Immune Response to Coxiella burnetii. Front Cell Infect Microbiol 2021; 11:754455. [PMID: 34796128 PMCID: PMC8593175 DOI: 10.3389/fcimb.2021.754455] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 10/12/2021] [Indexed: 12/14/2022] Open
Abstract
Coxiella burnetii is an obligate intracellular Gram-negative bacterium and the causative agent of a worldwide zoonosis known as Q fever. The pathogen invades monocytes and macrophages, replicating within acidic phagolysosomes and evading host defenses through different immune evasion strategies that are mainly associated with the structure of its lipopolysaccharide. The main transmission routes are aerosols and ingestion of fomites from infected animals. The innate immune system provides the first host defense against the microorganism, and it is crucial to direct the infection towards a self-limiting respiratory disease or the chronic form. This review reports the advances in understanding the mechanisms of innate immunity acting during C. burnetii infection and the strategies that pathogen put in place to infect the host cells and to modify the expression of specific host cell genes in order to subvert cellular processes. The mechanisms through which different cell types with different genetic backgrounds are differently susceptible to C. burnetii intracellular growth are discussed. The subsets of cytokines induced following C. burnetii infection as well as the pathogen influence on an inflammasome-mediated response are also described. Finally, we discuss the use of animal experimental systems for studying the innate immune response against C. burnetii and discovering novel methods for prevention and treatment of disease in humans and livestock.
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Affiliation(s)
- Guido Sireci
- Central Laboratory of Advanced Diagnostic and Biological Research (CLADIBIOR), Department of Biomedicine, Neurosciences and Advanced Diagnostics (BIND), University Hospital "Paolo Giaccone", Università degli studi di Palermo, Palermo, Italy
| | - Giusto Davide Badami
- Central Laboratory of Advanced Diagnostic and Biological Research (CLADIBIOR), Department of Biomedicine, Neurosciences and Advanced Diagnostics (BIND), University Hospital "Paolo Giaccone", Università degli studi di Palermo, Palermo, Italy
| | - Diana Di Liberto
- Central Laboratory of Advanced Diagnostic and Biological Research (CLADIBIOR), Department of Biomedicine, Neurosciences and Advanced Diagnostics (BIND), University Hospital "Paolo Giaccone", Università degli studi di Palermo, Palermo, Italy
| | - Valeria Blanda
- Istituto Zooprofilattico Sperimentale della Sicilia, Palermo, Italy
| | - Francesca Grippi
- Istituto Zooprofilattico Sperimentale della Sicilia, Palermo, Italy
| | - Laura Di Paola
- Istituto Zooprofilattico Sperimentale della Sicilia, Palermo, Italy
| | - Annalisa Guercio
- Istituto Zooprofilattico Sperimentale della Sicilia, Palermo, Italy
| | - José de la Fuente
- SaBio Health and Biotechnology, Instituto de Investigación en Recursos Cinegéticos, IREC -Spanish National Research Council CSIC - University of Castilla-La Mancha UCLM - Regional Government of Castilla-La Mancha JCCM, Ciudad Real, Spain.,Department of Veterinary Pathobiology, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK, United States
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8
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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; 203:e0037221. [PMID: 34309398 DOI: 10.1128/jb.00372-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [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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9
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Zouhir S, Contreras-Martel C, Maragno Trindade D, Attrée I, Dessen A, Macheboeuf P. MagC is a NplC/P60-like member of the α-2-macroglobulin Mag complex of Pseudomonas aeruginosa that interacts with peptidoglycan. FEBS Lett 2021; 595:2034-2046. [PMID: 34115884 DOI: 10.1002/1873-3468.14148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 05/17/2021] [Accepted: 06/08/2021] [Indexed: 11/07/2022]
Abstract
Bacterial α-2 macroglobulins (A2Ms) structurally resemble the large spectrum protease inhibitors of the eukaryotic immune system. In Pseudomonas aeruginosa, MagD acts as an A2M and is expressed within a six-gene operon encoding the MagA-F proteins. In this work, we employ isothermal calorimetry (ITC), analytical ultracentrifugation (AUC), and X-ray crystallography to investigate the function of MagC and show that MagC associates with the macroglobulin complex and with the peptidoglycan (PG). However, the catalytic residues of MagC display an inactive conformation that could suggest that it binds to PG but does not degrade it. We hypothesize that MagC could serve as an anchor between the MagD macroglobulin and the PG and could provide stabilization and/or regulation for the entire complex.
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Affiliation(s)
- Samira Zouhir
- Brazilian Biosciences National Laboratory (LNBio), CNPEM, Campinas, Brazil
| | | | | | - Ina Attrée
- Unité de Biologie Cellulaire et Infection, CEA, INSERM, CNRS, Université Grenoble Alpes, France
| | - Andréa Dessen
- Brazilian Biosciences National Laboratory (LNBio), CNPEM, Campinas, Brazil.,CNRS, CEA, IBS, Université Grenoble Alpes, France
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10
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CwlQ Is Required for Swarming Motility but Not Flagellar Assembly in Bacillus subtilis. J Bacteriol 2021; 203:JB.00029-21. [PMID: 33649146 DOI: 10.1128/jb.00029-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 02/22/2021] [Indexed: 11/20/2022] Open
Abstract
Lytic enzymes play an essential role in the remodeling of bacterial peptidoglycan (PG), an extracellular mesh-like structure that retains the membrane in the context of high internal osmotic pressure. Peptidoglycan must be unfailingly stable to preserve cell integrity, but must also be dynamically remodeled for the cell to grow, divide, and insert macromolecular machines. The flagellum is one such macromolecular machine that transits the PG, and flagellar insertion is aided by localized activity of a dedicated PG lyase in Gram-negative bacteria. To date, there is no known dedicated lyase in Gram-positive bacteria for the insertion of flagella. Here, we take a reverse-genetic candidate-gene approach and find that cells mutated for the lytic transglycosylase CwlQ exhibit a severe defect in flagellum-dependent swarming motility. We further show that CwlQ is expressed by the motility sigma factor SigD and is secreted by the type III secretion system housed inside the flagellum. Nonetheless, cells with mutations of CwlQ remain proficient for flagellar biosynthesis even when mutated in combination with four other lyases related to motility (LytC, LytD, LytF, and CwlO). The PG lyase (or lyases) essential for flagellar synthesis in B. subtilis, if any, remains unknown.IMPORTANCE Bacteria are surrounded by a wall of peptidoglycan and early work in Bacillus subtilis was the first to suggest that bacteria needed to enzymatically remodel the wall to permit insertion of the flagellum. No PG remodeling enzyme alone or in combination, however, has been found to be essential for flagellar assembly in B. subtilis Here, we take a reverse-genetic candidate-gene approach and find that the PG lytic transglycosylase CwlQ is required for swarming motility. Subsequent characterization determined that while CwlQ was coexpressed with motility genes and is secreted by the flagellar secretion apparatus, it was not required for flagellar synthesis. The PG lyase needed for flagellar assembly in B. subtilis remains unknown.
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11
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Straume D, Piechowiak KW, Kjos M, Håvarstein LS. Class A PBPs: It is time to rethink traditional paradigms. Mol Microbiol 2021; 116:41-52. [PMID: 33709487 DOI: 10.1111/mmi.14714] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 03/08/2021] [Accepted: 03/09/2021] [Indexed: 12/18/2022]
Abstract
Until recently, class A penicillin-binding proteins (aPBPs) were the only enzymes known to catalyze glycan chain polymerization from lipid II in bacteria. Hence, the discovery of two novel lipid II polymerases, FtsW and RodA, raises new questions and has consequently received a lot of attention from the research community. FtsW and RodA are essential and highly conserved members of the divisome and elongasome, respectively, and work in conjunction with their cognate class B PBPs (bPBPs) to synthesize the division septum and insert new peptidoglycan into the lateral cell wall. The identification of FtsW and RodA as peptidoglycan glycosyltransferases has raised questions regarding the role of aPBPs in peptidoglycan synthesis and fundamentally changed our understanding of the process. Despite their dethronement, aPBPs are essential in most bacteria. So, what is their function? In this review, we discuss recent progress in answering this question and present our own views on the topic.
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Affiliation(s)
- Daniel Straume
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, Norway
| | | | - Morten Kjos
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, Norway
| | - Leiv Sigve Håvarstein
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, Norway
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12
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Hennell James R, Deme JC, Kjӕr A, Alcock F, Silale A, Lauber F, Johnson S, Berks BC, Lea SM. Structure and mechanism of the proton-driven motor that powers type 9 secretion and gliding motility. Nat Microbiol 2021; 6:221-233. [PMID: 33432152 PMCID: PMC7116788 DOI: 10.1038/s41564-020-00823-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 10/28/2020] [Indexed: 12/11/2022]
Abstract
Three classes of ion-driven protein motors have been identified to date: ATP synthase, the bacterial flagellar motor and a proton-driven motor that powers gliding motility and the type 9 protein secretion system in Bacteroidetes bacteria. Here, we present cryo-electron microscopy structures of the gliding motility/type 9 protein secretion system motors GldLM from Flavobacterium johnsoniae and PorLM from Porphyromonas gingivalis. The motor is an asymmetric inner membrane protein complex in which the single transmembrane helices of two periplasm-spanning GldM/PorM proteins are positioned inside a ring of five GldL/PorL proteins. Mutagenesis and single-molecule tracking identify protonatable amino acid residues in the transmembrane domain of the complex that are important for motor function. Our data provide evidence for a mechanism in which proton flow results in rotation of the periplasm-spanning GldM/PorM dimer inside the intra-membrane GldL/PorL ring to drive processes at the bacterial outer membrane.
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Affiliation(s)
- Rory Hennell James
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Justin C Deme
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
- Department of Biochemistry, University of Oxford, Oxford, UK
- The Central Oxford Structural Molecular Imaging Centre (COSMIC), University of Oxford, Oxford, UK
| | - Andreas Kjӕr
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Felicity Alcock
- Department of Biochemistry, University of Oxford, Oxford, UK
- CBCB, Newcastle University, Newcastle upon Tyne, UK
| | - Augustinas Silale
- Department of Biochemistry, University of Oxford, Oxford, UK
- CBCB, Newcastle University, Newcastle upon Tyne, UK
| | - Frédéric Lauber
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Steven Johnson
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Ben C Berks
- Department of Biochemistry, University of Oxford, Oxford, UK.
| | - Susan M Lea
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK.
- The Central Oxford Structural Molecular Imaging Centre (COSMIC), University of Oxford, Oxford, UK.
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13
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Liston SD, Willis LM. Racing to build a wall: glycoconjugate assembly in Gram-positive and Gram-negative bacteria. Curr Opin Struct Biol 2021; 68:55-65. [PMID: 33429200 DOI: 10.1016/j.sbi.2020.11.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 11/20/2020] [Accepted: 11/22/2020] [Indexed: 12/17/2022]
Abstract
The last two years have seen major advances in understanding the structural basis of bacterial cell envelope glycoconjugate biosynthesis, including capsules, lipopolysaccharide, teichoic acid, cellulose, and peptidoglycan. The recent crystal and cryo-electron microscopy structures of proteins involved in the initial glycosyltransferase steps in the cytoplasm, the transport of large and small lipid-linked glycoconjugates across the inner membrane, the polymerization of glycans in the periplasm, and the export of molecules from the cell have shed light on the mechanisms by which cell envelope glycoconjugates are made. We discuss these recent advances and highlight remaining unanswered questions.
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Affiliation(s)
- Sean D Liston
- Department of Molecular Genetics, University of Toronto, Toronto, ON, M5G1M1, Canada
| | - Lisa M Willis
- Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G2T2, Canada; Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, AB, T6G2T2, Canada; Women and Children's Health Research Institute, Edmonton, AB, T6G2T2, Canada.
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14
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Rivera SL, Espaillat A, Aditham AK, Shieh P, Muriel-Mundo C, Kim J, Cava F, Siegrist MS. Chemically Induced Cell Wall Stapling in Bacteria. Cell Chem Biol 2020; 28:213-220.e4. [PMID: 33238158 DOI: 10.1016/j.chembiol.2020.11.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 09/09/2020] [Accepted: 11/06/2020] [Indexed: 12/16/2022]
Abstract
Transpeptidation reinforces the structure of cell-wall peptidoglycan, an extracellular heteropolymer that protects bacteria from osmotic lysis. The clinical success of transpeptidase-inhibiting β-lactam antibiotics illustrates the essentiality of these cross-linkages for cell-wall integrity, but the presence of multiple, seemingly redundant transpeptidases in many species makes it challenging to determine cross-link function. Here, we present a technique to link peptide strands by chemical rather than enzymatic reaction. We employ biocompatible click chemistry to induce triazole formation between azido- and alkynyl-d-alanine residues that are metabolically installed in the peptidoglycan of Gram-positive or Gram-negative bacteria. Synthetic triazole cross-links can be visualized using azidocoumarin-d-alanine, an amino acid derivative that undergoes fluorescent enhancement upon reaction with terminal alkynes. Cell-wall stapling protects Escherichia coli from treatment with the broad-spectrum β-lactams ampicillin and carbenicillin. Chemical control of cell-wall structure in live bacteria can provide functional insights that are orthogonal to those obtained by genetics.
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Affiliation(s)
- Sylvia L Rivera
- Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA
| | - Akbar Espaillat
- Laboratory for Molecular Infection Medicine, Department of Molecular Biology, Umeå University, Umeå 90187, Sweden
| | - Arjun K Aditham
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA; Stanford ChEM-H (Chemistry, Engineering, and Medicine for Human Health), Stanford University, Stanford, CA 94305, USA
| | - Peyton Shieh
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Chris Muriel-Mundo
- Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA
| | - Justin Kim
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Felipe Cava
- Laboratory for Molecular Infection Medicine, Department of Molecular Biology, Umeå University, Umeå 90187, Sweden.
| | - M Sloan Siegrist
- Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA; Molecular and Cellular Biology Program, University of Massachusetts, Amherst, MA 01003, USA.
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15
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Shin JH, Sulpizio AG, Kelley A, Alvarez L, Murphy SG, Fan L, Cava F, Mao Y, Saper MA, Dörr T. Structural basis of peptidoglycan endopeptidase regulation. Proc Natl Acad Sci U S A 2020; 117:11692-11702. [PMID: 32393643 PMCID: PMC7261138 DOI: 10.1073/pnas.2001661117] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Most bacteria surround themselves with a cell wall, a strong meshwork consisting primarily of the polymerized aminosugar peptidoglycan (PG). PG is essential for structural maintenance of bacterial cells, and thus for viability. PG is also constantly synthesized and turned over; the latter process is mediated by PG cleavage enzymes, for example, the endopeptidases (EPs). EPs themselves are essential for growth but also promote lethal cell wall degradation after exposure to antibiotics that inhibit PG synthases (e.g., β-lactams). Thus, EPs are attractive targets for novel antibiotics and their adjuvants. However, we have a poor understanding of how these enzymes are regulated in vivo, depriving us of novel pathways for the development of such antibiotics. Here, we have solved crystal structures of the LysM/M23 family peptidase ShyA, the primary EP of the cholera pathogen Vibrio cholerae Our data suggest that ShyA assumes two drastically different conformations: a more open form that allows for substrate binding and a closed form, which we predicted to be catalytically inactive. Mutations expected to promote the open conformation caused enhanced activity in vitro and in vivo, and these results were recapitulated in EPs from the divergent pathogens Neisseria gonorrheae and Escherichia coli Our results suggest that LysM/M23 EPs are regulated via release of the inhibitory Domain 1 from the M23 active site, likely through conformational rearrangement in vivo.
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Affiliation(s)
- Jung-Ho Shin
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853
| | - Alan G Sulpizio
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853
| | - Aaron Kelley
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109-5606
| | - Laura Alvarez
- The Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden
| | - Shannon G Murphy
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853
- Department of Microbiology, Cornell University, Ithaca, NY 14853
| | - Lixin Fan
- Basic Science Program, Frederick National Laboratory for Cancer Research, SAXS Core Facility of the National Cancer Institute, Frederick, MD 21702
| | - Felipe Cava
- The Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden
| | - Yuxin Mao
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853
| | - Mark A Saper
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109-5606
| | - Tobias Dörr
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853;
- Department of Microbiology, Cornell University, Ithaca, NY 14853
- Cornell Institute of Host-Microbe Interactions and Disease, Cornell University, Ithaca, NY 14853
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16
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Liu S, Zheng J, Hao L, Yegin Y, Bae M, Ulugun B, Taylor TM, Scholar EA, Cisneros-Zevallos L, Oh JK, Akbulut M. Dual-Functional, Superhydrophobic Coatings with Bacterial Anticontact and Antimicrobial Characteristics. ACS APPLIED MATERIALS & INTERFACES 2020; 12:21311-21321. [PMID: 32023023 DOI: 10.1021/acsami.9b18928] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Bacterial pathogens are responsible for millions of cases of illnesses and deaths each year throughout the world. The development of novel surfaces and coatings that effectively inhibit and prevent bacterial attachment, proliferation, and growth is one of the crucial steps for tackling this global challenge. Herein, we report a dual-functional coating for aluminum surfaces that relies on the controlled immobilization of lysozyme enzyme (muramidase) into interstitial spaces of presintered, nanostructured thin film based on ∼200 nm silica nanoparticles and the sequential chemisorption of an organofluorosilane to the available interfacial areas. The mean diameter of the resultant lysozyme microdomains was 3.1 ± 2.5 μm with an average spacing of 8.01 ± 6.8 μm, leading to a surface coverage of 15.32%. The coating had an overall root-mean-square (rms) roughness of 539 ± 137 nm and roughness factor of 1.50 ± 0.1, and demonstrated static, advancing, and receding water contact angles of 159.0 ± 1.0°, 155.4 ± 0.6°, and 154.4 ± 0.6°, respectively. Compared to the planar aluminum, the coated surfaces produced a 6.5 ± 0.1 (>99.99997%) and 4.0 ± 0.1 (>99.99%) log-cycle reductions in bacterial surfaces colonization against Gram-negative Salmonella Typhimurium LT2 and Gram-positive Listeria innocua, respectively. We anticipate that the implementation of such a coating strategy on healthcare environments and surfaces and food-contact surfaces can significantly reduce or eliminate potential risks associated with various contamination and cross-contamination scenarios.
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Affiliation(s)
- Shuhao Liu
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843, United States
| | - Jeremy Zheng
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas 77843, United States
| | - Li Hao
- School of Chemistry and Chemical Engineering, Zhongkai University of Agriculture and Engineering, Guangzhou 510408, People's Republic of China
| | - Yagmur Yegin
- Department of Nutrition and Food Science, Texas A&M University, College Station, Texas 77843, United States
| | - Michael Bae
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843, United States
| | - Beril Ulugun
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas 77843, United States
| | - Thomas Matthew Taylor
- Department of Nutrition and Food Science, Texas A&M University, College Station, Texas 77843, United States
| | - Ethan A Scholar
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843, United States
| | - Luis Cisneros-Zevallos
- Department of Nutrition and Food Science, Texas A&M University, College Station, Texas 77843, United States
- Department of Horticultural Sciences, Texas A&M University, College Station, Texas 77843, United States
| | - Jun Kyun Oh
- Department of Polymer Science and Engineering, Dankook University, 152 Jukjeon-ro, Suji-gu, Yongin-si, Gyeonggi-do 16890, Republic of Korea
| | - Mustafa Akbulut
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843, United States
- Department of Materials Science and Engineering, Texas A&M University, College Station, Texas 77843, United States
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17
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Trinh NTT, Tran HQ, Van Dong Q, Cambillau C, Roussel A, Leone P. Crystal structure of Type IX secretion system PorE C-terminal domain from Porphyromonas gingivalis in complex with a peptidoglycan fragment. Sci Rep 2020; 10:7384. [PMID: 32355178 PMCID: PMC7192894 DOI: 10.1038/s41598-020-64115-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 03/31/2020] [Indexed: 02/06/2023] Open
Abstract
Porphyromonas gingivalis, the major human pathogen associated to periodontal diseases, utilizes the Bacteroidetes-specific type IX secretion system (T9SS) to export virulence factors. PorE is a periplasmic multi-domain lipoprotein associated to the outer membrane that was recently identified as essential for T9SS function. Little is known on T9SS at the structural level, and in particular its interaction with peptidoglycan. This prompted us to carry out structural studies on PorE full length as well as on its four isolated domains. Here we report the crystal structure of the C-terminal OmpA_C-like putative peptidoglycan-binding domain at 1.55 Å resolution. An electron density volume was identified in the protein cleft, making it possible to build a naturally-occurring peptidoglycan fragment. This result suggests that PorE interacts with peptidoglycan and that PorE could anchor T9SS to the cell wall.
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Affiliation(s)
- Nhung Thi Trang Trinh
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, UMR 7257, 163 Avenue de Luminy, Case 932, 13009, Marseille, France.,Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique, UMR 7257, 163 Avenue de Luminy, Case 932, 13009, Marseille, France.,Faculty of Medical Technology, PHENIKAA University, Yen Nghia, Ha Dong, Hanoi 12116, Vietnam.,PHENIKAA Research and Technology Institute (PRATI), A&A Green Phoenix Group JSC, No. 167 Hoang Ngan, Trung Hoa, Cau Giay, Hanoi 11313, Vietnam
| | - Hieu Quang Tran
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, UMR 7257, 163 Avenue de Luminy, Case 932, 13009, Marseille, France.,Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique, UMR 7257, 163 Avenue de Luminy, Case 932, 13009, Marseille, France
| | - Quyen Van Dong
- Institute of Biotechnology, Vietnam Academy of Science and Technology. 18 Hoang Quoc Viet, Ha Noi, Vietnam.,University of Science and Technology of Hanoi, Vietnam Academy of Science and Technology. 18 Hoang Quoc Viet, Ha Noi, Vietnam
| | - Christian Cambillau
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, UMR 7257, 163 Avenue de Luminy, Case 932, 13009, Marseille, France.,Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique, UMR 7257, 163 Avenue de Luminy, Case 932, 13009, Marseille, France
| | - Alain Roussel
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, UMR 7257, 163 Avenue de Luminy, Case 932, 13009, Marseille, France.,Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique, UMR 7257, 163 Avenue de Luminy, Case 932, 13009, Marseille, France
| | - Philippe Leone
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, UMR 7257, 163 Avenue de Luminy, Case 932, 13009, Marseille, France. .,Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique, UMR 7257, 163 Avenue de Luminy, Case 932, 13009, Marseille, France.
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18
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Baidya AK, Rosenshine I, Ben-Yehuda S. Donor-delivered cell wall hydrolases facilitate nanotube penetration into recipient bacteria. Nat Commun 2020; 11:1938. [PMID: 32321911 PMCID: PMC7176660 DOI: 10.1038/s41467-020-15605-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Accepted: 03/16/2020] [Indexed: 11/09/2022] Open
Abstract
Bacteria can produce membranous nanotubes that mediate contact-dependent exchange of molecules among bacterial cells. However, it is unclear how nanotubes cross the cell wall to emerge from the donor or to penetrate into the recipient cell. Here, we report that Bacillus subtilis utilizes cell wall remodeling enzymes, the LytC amidase and its enhancer LytB, for efficient nanotube extrusion and penetration. Nanotube production is reduced in a lytBC mutant, and the few nanotubes formed appear deficient in penetrating into target cells. Donor-derived LytB molecules localize along nanotubes and on the surface of nanotube-connected neighbouring cells, primarily at sites of nanotube penetration. Furthermore, LytB from donor B. subtilis can activate LytC of recipient bacteria from diverse species, facilitating cell wall hydrolysis to establish nanotube connection. Our data provide a mechanistic view of how intercellular connecting devices can be formed among neighbouring bacteria. Bacteria can produce membranous nanotubes that mediate contact-dependent exchange of molecules between bacterial cells. Here, Baidya et al. show that cell-wall remodelling enzymes from Bacillus subtilis are required for efficient nanotube extrusion and penetration, and can be delivered to other bacterial species via nanotubes.
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Affiliation(s)
- Amit K Baidya
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, The Hebrew University of Jerusalem, POB 12272, 91120, Jerusalem, Israel
| | - Ilan Rosenshine
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, The Hebrew University of Jerusalem, POB 12272, 91120, Jerusalem, Israel
| | - Sigal Ben-Yehuda
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, The Hebrew University of Jerusalem, POB 12272, 91120, Jerusalem, Israel.
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19
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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; 117:6129-6138. [PMID: 32123104 PMCID: PMC7084106 DOI: 10.1073/pnas.1917820117] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [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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20
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Anderson EM, Sychantha D, Brewer D, Clarke AJ, Geddes-McAlister J, Khursigara CM. Peptidoglycomics reveals compositional changes in peptidoglycan between biofilm- and planktonic-derived Pseudomonas aeruginosa. J Biol Chem 2019; 295:504-516. [PMID: 31771981 DOI: 10.1074/jbc.ra119.010505] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Revised: 11/25/2019] [Indexed: 12/14/2022] Open
Abstract
Peptidoglycan (PG) is a critical component of the bacterial cell wall and is composed of a repeating β-1,4-linked disaccharide of N-acetylglucosamine and N-acetylmuramic acid appended with a highly conserved stem peptide. In Gram-negative bacteria, PG is assembled in the cytoplasm and exported into the periplasm where it undergoes considerable maturation, modification, or degradation depending on the growth phase or presence of environmental stressors. These modifications serve important functions in diverse processes, including PG turnover, cell elongation/division, and antibiotic resistance. Conventional methods for analyzing PG composition are complex and time-consuming. We present here a streamlined MS-based method that combines differential analysis with statistical 1D annotation approaches to quantitatively compare PGs produced in planktonic- and biofilm-cultured Pseudomonas aeruginosa We identified a core assembly of PG that is present in high abundance and that does not significantly differ between the two growth states. We also identified an adaptive PG assembly that is present in smaller amounts and fluctuates considerably between growth states in response to physiological changes. Biofilm-derived adaptive PG exhibited significant changes compared with planktonic-derived PG, including amino acid substitutions of the stem peptide and modifications that indicate changes in the activity of amidases, deacetylases, and lytic transglycosylases. The results of this work also provide first evidence of de-N-acetylated muropeptides from P. aeruginosa The method developed here offers a robust and reproducible workflow for accurately determining PG composition in samples that can be used to assess global PG fluctuations in response to changing growth conditions or external stimuli.
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Affiliation(s)
- Erin M Anderson
- Department of Molecular and Cellular Biology, University of Guelph, Ontario N1G 2W1, Canada
| | - David Sychantha
- Department of Molecular and Cellular Biology, University of Guelph, Ontario N1G 2W1, Canada
| | - Dyanne Brewer
- Mass Spectrometry Facility, University of Guelph, Ontario N1G 2W1, Canada
| | - Anthony J Clarke
- Department of Molecular and Cellular Biology, University of Guelph, Ontario N1G 2W1, Canada
| | - Jennifer Geddes-McAlister
- Department of Molecular and Cellular Biology, University of Guelph, Ontario N1G 2W1, Canada; Mass Spectrometry Facility, University of Guelph, Ontario N1G 2W1, Canada.
| | - Cezar M Khursigara
- Department of Molecular and Cellular Biology, University of Guelph, Ontario N1G 2W1, Canada; Mass Spectrometry Facility, University of Guelph, Ontario N1G 2W1, Canada.
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21
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Wang J, Brodmann M, Basler M. Assembly and Subcellular Localization of Bacterial Type VI Secretion Systems. Annu Rev Microbiol 2019; 73:621-638. [DOI: 10.1146/annurev-micro-020518-115420] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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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22
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Dörr T, Moynihan PJ, Mayer C. Editorial: Bacterial Cell Wall Structure and Dynamics. Front Microbiol 2019; 10:2051. [PMID: 31551985 PMCID: PMC6737391 DOI: 10.3389/fmicb.2019.02051] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 08/20/2019] [Indexed: 12/23/2022] Open
Affiliation(s)
- Tobias Dörr
- Department of Microbiology, Weill Institute for Cell and Molecular Biology, Ithaca, NY, United States.,Cornell Institute of Host-Microbe Interactions and Disease, Cornell University, Ithaca, NY, United States
| | - Patrick J Moynihan
- School of Biosciences, Institute of Microbiology and Infection, University of Birmingham, Birmingham, United Kingdom
| | - Christoph Mayer
- Department of Biology, Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
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23
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Wang L, Yang LY, Gan YL, Yang F, Liang XL, Li WL, Bo-Le J. Two lytic transglycosylases of Xanthomonas campestris pv. campestris associated with cell separation and type III secretion system, respectively. FEMS Microbiol Lett 2019; 366:5449009. [PMID: 30977795 DOI: 10.1093/femsle/fnz073] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 04/09/2019] [Indexed: 01/13/2023] Open
Abstract
The lytic transglycosylases (LTs) are important enzymes that degrade peptidoglycan of the bacterial cell wall and affect many biological functions. We present here that XC_0706 and XC_3001 are annotated as the LTs in Xanthomonas campestris pv. campestris. XC_0706 is associated with virulence and plays a pivotal role in cell division. Mutation on XC_3001 reduced hypersensitive response induction and the translocation of type III effector, but did not affect the function of the type II secretion system. Further studies showed that multiple LTs genes contribute to efficiency of the type III secretory system in X. campestris pv. campestris.
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Affiliation(s)
- Lin Wang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China.,College of Biotechnology, Guilin Medical University, 109 North 2nd Huancheng Road, Guilin, Guangxi 541004, China
| | - Li-Yan Yang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
| | - Yong-Liang Gan
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
| | - Feng Yang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
| | - Xue-Lian Liang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
| | - Wan-Lian Li
- College of Biotechnology, Guilin Medical University, 109 North 2nd Huancheng Road, Guilin, Guangxi 541004, China
| | - Jiang Bo-Le
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
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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: 108] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [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)
| | | | - 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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Coxiella burnetii RpoS Regulates Genes Involved in Morphological Differentiation and Intracellular Growth. J Bacteriol 2019; 201:JB.00009-19. [PMID: 30745369 DOI: 10.1128/jb.00009-19] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 01/30/2019] [Indexed: 12/19/2022] Open
Abstract
Coxiella burnetii, the etiological agent of Q fever, undergoes a unique biphasic developmental cycle where bacteria transition from a replicating (exponential-phase) large cell variant (LCV) form to a nonreplicating (stationary-phase) small cell variant (SCV) form. The alternative sigma factor RpoS is an essential regulator of stress responses and stationary-phase physiology in several bacterial species, including Legionella pneumophila, which has a developmental cycle superficially similar to that of C. burnetii Here, we used a C. burnetii ΔrpoS mutant to define the role of RpoS in intracellular growth and SCV development. Growth yields following infection of Vero epithelial cells or THP-1 macrophage-like cells with the rpoS mutant in the SCV form, but not the LCV form, were significantly lower than that of wild-type bacteria. RNA sequencing and whole-cell mass spectrometry of the C. burnetii ΔrpoS mutant revealed that a substantial portion of the C. burnetii genome is regulated by RpoS during SCV development. Regulated genes include those involved in stress responses, arginine transport, peptidoglycan remodeling, and synthesis of the SCV-specific protein ScvA. Genes comprising the dot/icm locus, responsible for production of the Dot/Icm type 4B secretion system, were also dysregulated in the rpoS mutant. These data were corroborated with independent assays demonstrating that the C. burnetii ΔrpoS strain has increased sensitivity to hydrogen peroxide and carbenicillin and a thinner cell wall/outer membrane complex. Collectively, these results demonstrate that RpoS is an important regulator of genes involved in C. burnetii SCV development and intracellular growth.IMPORTANCE The Q fever bacterium Coxiella burnetii has spore-like environmental stability, a characteristic that contributes to its designation as a potential bioweapon. Stability is likely conferred by a highly resistant, small cell variant (SCV) stationary-phase form that arises during a biphasic developmental cycle. Here, we define the role of the alternative sigma factor RpoS in regulating genes associated with SCV development. Genes involved in stress responses, amino acid transport, cell wall remodeling, and type 4B effector secretion were dysregulated in the rpoS mutant. Cellular impairments included defects in intracellular growth, cell wall structure, and resistance to oxidants. These results support RpoS as a central regulator of the Coxiella developmental cycle and identify developmentally regulated genes involved in morphological differentiation.
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Vermassen A, Leroy S, Talon R, Provot C, Popowska M, Desvaux M. Cell Wall Hydrolases in Bacteria: Insight on the Diversity of Cell Wall Amidases, Glycosidases and Peptidases Toward Peptidoglycan. Front Microbiol 2019; 10:331. [PMID: 30873139 PMCID: PMC6403190 DOI: 10.3389/fmicb.2019.00331] [Citation(s) in RCA: 179] [Impact Index Per Article: 35.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Accepted: 02/08/2019] [Indexed: 11/13/2022] Open
Abstract
The cell wall (CW) of bacteria is an intricate arrangement of macromolecules, at least constituted of peptidoglycan (PG) but also of (lipo)teichoic acids, various polysaccharides, polyglutamate and/or proteins. During bacterial growth and division, there is a constant balance between CW degradation and biosynthesis. The CW is remodeled by bacterial hydrolases, whose activities are carefully regulated to maintain cell integrity or lead to bacterial death. Each cell wall hydrolase (CWH) has a specific role regarding the PG: (i) cell wall amidase (CWA) cleaves the amide bond between N-acetylmuramic acid and L-alanine residue at the N-terminal of the stem peptide, (ii) cell wall glycosidase (CWG) catalyses the hydrolysis of the glycosidic linkages, whereas (iii) cell wall peptidase (CWP) cleaves amide bonds between amino acids within the PG chain. After an exhaustive overview of all known conserved catalytic domains responsible for CWA, CWG, and CWP activities, this review stresses that the CWHs frequently display a modular architecture combining multiple and/or different catalytic domains, including some lytic transglycosylases as well as CW binding domains. From there, direct physiological and collateral roles of CWHs in bacterial cells are further discussed.
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Affiliation(s)
- Aurore Vermassen
- Université Clermont Auvergne, INRA, MEDiS, Clermont-Ferrand, France
| | - Sabine Leroy
- Université Clermont Auvergne, INRA, MEDiS, Clermont-Ferrand, France
| | - Régine Talon
- Université Clermont Auvergne, INRA, MEDiS, Clermont-Ferrand, France
| | | | - Magdalena Popowska
- Department of Applied Microbiology, Faculty of Biology, Institute of Microbiology, University of Warsaw, Warsaw, Poland
| | - Mickaël Desvaux
- Université Clermont Auvergne, INRA, MEDiS, Clermont-Ferrand, France
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Lonergan ZR, Nairn BL, Wang J, Hsu YP, Hesse LE, Beavers WN, Chazin WJ, Trinidad JC, VanNieuwenhze MS, Giedroc DP, Skaar EP. An Acinetobacter baumannii, Zinc-Regulated Peptidase Maintains Cell Wall Integrity during Immune-Mediated Nutrient Sequestration. Cell Rep 2019; 26:2009-2018.e6. [PMID: 30784584 PMCID: PMC6441547 DOI: 10.1016/j.celrep.2019.01.089] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 12/21/2018] [Accepted: 01/24/2019] [Indexed: 01/10/2023] Open
Abstract
Acinetobacter baumannii is an important nosocomial pathogen capable of causing wound infections, pneumonia, and bacteremia. During infection, A. baumannii must acquire Zn to survive and colonize the host. Vertebrates have evolved mechanisms to sequester Zn from invading pathogens by a process termed nutritional immunity. One of the most upregulated genes during Zn starvation encodes a putative cell wall-modifying enzyme which we named ZrlA. We found that inactivation of zrlA diminished growth of A. baumannii during Zn starvation. Additionally, this mutant strain displays increased cell envelope permeability, decreased membrane barrier function, and aberrant peptidoglycan muropeptide abundances. This altered envelope increases antibiotic efficacy both in vitro and in an animal model of A. baumannii pneumonia. These results establish ZrlA as a crucial link between nutrient metal uptake and cell envelope homeostasis during A. baumannii pathogenesis, which could be targeted for therapeutic development.
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Affiliation(s)
- Zachery R Lonergan
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA; Microbe-Host Interactions Training Program, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Brittany L Nairn
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Jiefei Wang
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA; Department of Chemistry, Indiana University, Bloomington, IN, USA
| | - Yen-Pang Hsu
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA
| | - Laura E Hesse
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA; Microbe-Host Interactions Training Program, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - William N Beavers
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Walter J Chazin
- Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Chemistry, Vanderbilt University, Nashville, TN, USA; Vanderbilt Institute for Infection, Immunology, and Inflammation, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Jonathan C Trinidad
- Department of Chemistry, Indiana University, Bloomington, IN, USA; Laboratory for Biological Mass Spectrometry, Department of Chemistry, Indiana University, Bloomington, IN, USA
| | - Michael S VanNieuwenhze
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA; Department of Chemistry, Indiana University, Bloomington, IN, USA
| | - David P Giedroc
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA; Department of Chemistry, Indiana University, Bloomington, IN, USA
| | - Eric P Skaar
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA; Vanderbilt Institute for Infection, Immunology, and Inflammation, Vanderbilt University Medical Center, Nashville, TN, USA.
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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] [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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Biochemical and Phylogenetic Study of SltF, a Flagellar Lytic Transglycosylase from Rhodobacter sphaeroides. J Bacteriol 2018; 200:JB.00397-18. [PMID: 30061356 DOI: 10.1128/jb.00397-18] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [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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EssH Peptidoglycan Hydrolase Enables Staphylococcus aureus Type VII Secretion across the Bacterial Cell Wall Envelope. J Bacteriol 2018; 200:JB.00268-18. [PMID: 30082459 DOI: 10.1128/jb.00268-18] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 07/31/2018] [Indexed: 11/20/2022] Open
Abstract
The ESAT-6-like secretion system (ESS) of Staphylococcus aureus is assembled in the bacterial membrane from core components that promote the secretion of WXG-like proteins (EsxA, EsxB, EsxC, and EsxD) and the EssD effector. Genes encoding the ESS secretion machinery components, effector, and WXG-like proteins are located in the ess locus. Here, we identify essH, a heretofore uncharacterized gene of the ess locus, whose product is secreted via an N-terminal signal peptide into the extracellular medium of staphylococcal cultures. EssH exhibits two peptidoglycan hydrolase activities, cleaving the pentaglycine cross bridge and the amide bond of N-acetylmuramyl-l-alanine, thereby separating glycan chains and wall peptides with cleaved cross bridges. Unlike other peptidoglycan hydrolases, EssH does not promote the lysis of staphylococci. EssH residues Cys199 and His254, which are conserved in other CHAP domain enzymes, are required for peptidoglycan hydrolase activity and for S. aureus ESS secretion. These data suggest that EssH and its murein hydrolase activity are required for protein secretion by the ESS pathway.IMPORTANCE Gene clusters encoding WXG-like proteins and FtsK/SpoIIIE-like P loop ATPases in Firmicutes encode type 7b secretion systems (T7bSS) for the transport of select protein substrates. The Staphylococcus aureus T7bSS assembles in the bacterial membrane and promotes the secretion of WXG-like proteins and effectors. The mechanisms whereby staphylococci extend the T7SS across the bacterial cell wall envelope are not known. Here, we show that staphylococci secrete EssH to cleave their peptidoglycan, thereby enabling T7bSS transport of proteins across the bacterial cell wall envelope.
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Abstract
Carboxy-terminal processing proteases (CTPs) occur in all three domains of life. In bacteria, some of them have been associated with virulence. However, the precise roles of bacterial CTPs are poorly understood, and few direct proteolytic substrates have been identified. One bacterial CTP is the CtpA protease of Pseudomonas aeruginosa, which is required for type III secretion system (T3SS) function and for virulence in a mouse model of acute pneumonia. Here, we have investigated the function of CtpA in P. aeruginosa and identified some of the proteins it cleaves. We discovered that CtpA forms a complex with a previously uncharacterized protein, which we have named LbcA (lipoprotein binding partner of CtpA). LbcA is required for CtpA activity in vivo and promotes its activity in vitro. We have also identified four proteolytic substrates of CtpA, all of which are uncharacterized proteins predicted to cleave the peptide cross-links within peptidoglycan. Consistent with this, a ctpA null mutant was found to have fewer peptidoglycan cross-links than the wild type and grew slowly in salt-free medium. Intriguingly, the accumulation of just one of the CtpA substrates was required for some ΔctpA mutant phenotypes, including the defective T3SS. We propose that LbcA-CtpA is a proteolytic complex in the P. aeruginosa cell envelope, which controls the activity of several peptidoglycan cross-link hydrolases by degrading them. Furthermore, based on these and other findings, we suggest that many bacterial CTPs might be similarly controlled by partner proteins as part of a widespread mechanism to control peptidoglycan hydrolase activity. Bacterial carboxy-terminal processing proteases (CTPs) are widely conserved and have been associated with the virulence of several species. However, their roles are poorly understood, and few direct substrates have been identified in any species. Pseudomonas aeruginosa is an important human pathogen in which one CTP, known as CtpA, is required for type III secretion system function and for virulence. This work provides an important advance by showing that CtpA works with a previously uncharacterized binding partner to degrade four substrates. These substrates are all predicted to hydrolyze peptidoglycan cross-links, suggesting that the CtpA complex is an important control mechanism for peptidoglycan hydrolysis. This is likely to emerge as a widespread mechanism used by diverse bacteria to control some of their peptidoglycan hydrolases. This is significant, given the links between CTPs and virulence in several pathogens and the importance of peptidoglycan remodeling to almost all bacterial cells.
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Yang L, Gan Y, Yang L, Jiang B, Tang J. Peptidoglycan hydrolysis mediated by the amidase AmiC and its LytM activator NlpD is critical for cell separation and virulence in the phytopathogen Xanthomonas campestris. MOLECULAR PLANT PATHOLOGY 2018; 19:1705-1718. [PMID: 29240286 PMCID: PMC6638016 DOI: 10.1111/mpp.12653] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 11/10/2017] [Accepted: 12/11/2017] [Indexed: 06/07/2023]
Abstract
The essential stages of bacterial cell separation are described as the synthesis and hydrolysis of septal peptidoglycan (PG). The amidase, AmiC, which cleaves the peptide side-chains linked to the glycan strands, contributes critically to this process and has been studied extensively in model strains of Escherichia coli. However, insights into the contribution of this protein to other processes in the bacterial cell have been limited. Xanthomonas campestris pv. campestris (Xcc) is a phytopathogen that causes black rot disease in many economically important plants. We investigated how AmiC and LytM family regulators, NlpD and EnvC, contribute to virulence and cell separation in this organism. Biochemical analyses of purified AmiC demonstrated that it could hydrolyse PG and its activity could be potentiated by the presence of the regulator NlpD. We also established that deletion of the genes encoding amiC1 or nlpD led to a reduction in virulence as well as effects on colony-forming units and cell morphology. Moreover, further genetic and biochemical evidence showed that AmiC1 and NlpD affect the secretion of type III effector XC3176 and hypersensitive response (HR) induction in planta. These findings indicate that, in addition to their well-studied role(s) in cell separation, AmiC and NlpD make an important contribution to the type III secretion (T3S) and virulence regulation in this important plant pathogen.
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Affiliation(s)
- Li‐Chao Yang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐bioresources, College of Life Science and TechnologyGuangxi UniversityNanningGuangxi 530004China
| | - Yong‐Liang Gan
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐bioresources, College of Life Science and TechnologyGuangxi UniversityNanningGuangxi 530004China
| | - Li‐Yan Yang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐bioresources, College of Life Science and TechnologyGuangxi UniversityNanningGuangxi 530004China
| | - Bo‐Le Jiang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐bioresources, College of Life Science and TechnologyGuangxi UniversityNanningGuangxi 530004China
| | - Ji‐Liang Tang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐bioresources, College of Life Science and TechnologyGuangxi UniversityNanningGuangxi 530004China
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Abstract
Bacteria have developed a number of trans-envelope systems to transport molecules or assemble organelles across bacterial envelopes. However, bacterial envelopes contain a rigid netlike peptidoglycan structure that protects cells from osmotic lysis. Trans-envelope systems thus must interact with the peptidoglycan barrier to generate gaps or anchor structures to the peptidoglycan scaffold. Here we describe methods to use in vivo cross-linking and in vitro co-sedimentation to study protein-peptidoglycan interactions in Gram-negative bacteria. In particular, we address important considerations to ensure the specificity of the interactions in question.
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Abstract
Mycobacterial 6-kDa early secreted antigenic target (ESAT-6) system (ESX) exporters transport proteins across the cytoplasmic membrane. Many proteins transported by ESX systems are then translocated across the mycobacterial cell envelope and secreted from the cell. Although the mechanism underlying protein transport across the mycolate outer membrane remains elusive, the ESX systems are closely connected with and localize to the cell envelope. Links between ESX-associated proteins, cell wall synthesis, and the maintenance of cell envelope integrity have been reported. Genes encoding the ESX systems and those required for biosynthesis of the mycobacterial envelope are coregulated. Here, we review the interplay between ESX systems and the mycobacterial cell envelope.
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Dik DA, Marous DR, Fisher JF, Mobashery S. Lytic transglycosylases: concinnity in concision of the bacterial cell wall. Crit Rev Biochem Mol Biol 2017. [PMID: 28644060 DOI: 10.1080/10409238.2017.1337705] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The lytic transglycosylases (LTs) are bacterial enzymes that catalyze the non-hydrolytic cleavage of the peptidoglycan structures of the bacterial cell wall. They are not catalysts of glycan synthesis as might be surmised from their name. Notwithstanding the seemingly mundane reaction catalyzed by the LTs, their lytic reactions serve bacteria for a series of astonishingly diverse purposes. These purposes include cell-wall synthesis, remodeling, and degradation; for the detection of cell-wall-acting antibiotics; for the expression of the mechanism of cell-wall-acting antibiotics; for the insertion of secretion systems and flagellar assemblies into the cell wall; as a virulence mechanism during infection by certain Gram-negative bacteria; and in the sporulation and germination of Gram-positive spores. Significant advances in the mechanistic understanding of each of these processes have coincided with the successive discovery of new LTs structures. In this review, we provide a systematic perspective on what is known on the structure-function correlations for the LTs, while simultaneously identifying numerous opportunities for the future study of these enigmatic enzymes.
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Affiliation(s)
- David A Dik
- a Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN , USA
| | - Daniel R Marous
- a Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN , USA
| | - Jed F Fisher
- a Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN , USA
| | - Shahriar Mobashery
- a Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN , USA
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Alterations in Peptidoglycan Cross-Linking Suppress the Secretin Assembly Defect Caused by Mutation of GspA in the Type II Secretion System. J Bacteriol 2017; 199:JB.00617-16. [PMID: 28138102 DOI: 10.1128/jb.00617-16] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Accepted: 01/23/2017] [Indexed: 12/22/2022] Open
Abstract
In Gram-negative bacteria, the peptidoglycan (PG) cell wall is a significant structural barrier for outer membrane protein assembly. In Aeromonas hydrophila, outer membrane multimerization of the type II secretion system (T2SS) secretin ExeD requires the function of the inner membrane assembly factor complex ExeAB. The putative mechanism of the complex involves the reorganization of PG and localization of ExeD, whereby ExeA functions by interacting with PG to form a site for secretin assembly and ExeB forms an interaction with ExeD. This mechanism led us to hypothesize that increasing the pore size of PG would circumvent the requirement for ExeA in the assembly of the ExeD secretin. Growth of A. hydrophila in 270 mM Gly reduced PG cross-links by approximately 30% and led to the suppression of secretin assembly defects in exeA strains and in those expressing ExeA mutants by enabling localization of the secretin in the outer membrane. We also established a heterologous ExeD assembly system in Escherichia coli and showed that ExeAB and ExeC are the only A. hydrophila proteins required for the assembly of the ExeD secretin in E. coli and that ExeAB-independent assembly of ExeD can occur upon overexpression of the d,d-carboxypeptidase PBP 5. These results support an assembly model in which, upon binding to PG, ExeA induces multimerization and pore formation in the sacculus, which enables ExeD monomers to interact with ExeB and assemble into a secretin that both is inserted in the outer membrane and crosses the PG layer to interact with the inner membrane platform of the T2SS.IMPORTANCE The PG layer imposes a strict structural impediment for the assembly of macromolecular structures that span the cell envelope and serve as virulence factors in Gram-negative species. This work revealed that by decreasing PG cross-linking by growth in Gly, the absolute requirement for the PG-binding activity of ExeA in the assembly of the ExeD secretin was alleviated in A. hydrophila In a heterologous assembly model in E. coli, expression of the carboxypeptidase PBP 5 could relieve the requirement for ExeAB in the assembly of the ExeD secretin. These results provide some mechanistic details of the ExeAB assembly complex function, in which the PG-binding and oligomerization functions of ExeAB are used to create a pore in the PG that is required for secretin assembly.
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Mesarich CH, Rees-George J, Gardner PP, Ghomi FA, Gerth ML, Andersen MT, Rikkerink EHA, Fineran PC, Templeton MD. Transposon insertion libraries for the characterization of mutants from the kiwifruit pathogen Pseudomonas syringae pv. actinidiae. PLoS One 2017; 12:e0172790. [PMID: 28249011 PMCID: PMC5332098 DOI: 10.1371/journal.pone.0172790] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Accepted: 02/09/2017] [Indexed: 01/15/2023] Open
Abstract
Pseudomonas syringae pv. actinidiae (Psa), the causal agent of kiwifruit canker, is one of the most devastating plant diseases of recent times. We have generated two mini-Tn5-based random insertion libraries of Psa ICMP 18884. The first, a 'phenotype of interest' (POI) library, consists of 10,368 independent mutants gridded into 96-well plates. By replica plating onto selective media, the POI library was successfully screened for auxotrophic and motility mutants. Lipopolysaccharide (LPS) biosynthesis mutants with 'Fuzzy-Spreader'-like morphologies were also identified through a visual screen. The second, a 'mutant of interest' (MOI) library, comprises around 96,000 independent mutants, also stored in 96-well plates, with approximately 200 individuals per well. The MOI library was sequenced on the Illumina MiSeq platform using Transposon-Directed Insertion site Sequencing (TraDIS) to map insertion sites onto the Psa genome. A grid-based PCR method was developed to recover individual mutants, and using this strategy, the MOI library was successfully screened for a putative LPS mutant not identified in the visual screen. The Psa chromosome and plasmid had 24,031 and 1,236 independent insertion events respectively, giving insertion frequencies of 3.65 and 16.6 per kb respectively. These data suggest that the MOI library is near saturation, with the theoretical probability of finding an insert in any one chromosomal gene estimated to be 97.5%. However, only 47% of chromosomal genes had insertions. This surprisingly low rate cannot be solely explained by the lack of insertions in essential genes, which would be expected to be around 5%. Strikingly, many accessory genes, including most of those encoding type III effectors, lacked insertions. In contrast, 94% of genes on the Psa plasmid had insertions, including for example, the type III effector HopAU1. These results suggest that some chromosomal sites are rendered inaccessible to transposon insertion, either by DNA-binding proteins or by the architecture of the nucleoid.
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Affiliation(s)
- Carl H. Mesarich
- Bioprotection Portfolio, The New Zealand Institute for Plant & Food Research Limited, Auckland, New Zealand
- Laboratory of Molecular Plant Pathology, Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand
- Bio-Protection Research Centre, New Zealand
| | - Jonathan Rees-George
- Bioprotection Portfolio, The New Zealand Institute for Plant & Food Research Limited, Auckland, New Zealand
| | - Paul P. Gardner
- Bio-Protection Research Centre, New Zealand
- School of Biological Sciences, University of Canterbury, Christchurch, New Zealand
| | - Fatemeh Ashari Ghomi
- Bio-Protection Research Centre, New Zealand
- School of Biological Sciences, University of Canterbury, Christchurch, New Zealand
| | - Monica L. Gerth
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Mark T. Andersen
- Bioprotection Portfolio, The New Zealand Institute for Plant & Food Research Limited, Auckland, New Zealand
| | - Erik H. A. Rikkerink
- Bioprotection Portfolio, The New Zealand Institute for Plant & Food Research Limited, Auckland, New Zealand
| | - Peter C. Fineran
- Bio-Protection Research Centre, New Zealand
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Matthew D. Templeton
- Bioprotection Portfolio, The New Zealand Institute for Plant & Food Research Limited, Auckland, New Zealand
- Bio-Protection Research Centre, New Zealand
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
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Weber BS, Kinsella RL, Harding CM, Feldman MF. The Secrets of Acinetobacter Secretion. Trends Microbiol 2017; 25:532-545. [PMID: 28216293 DOI: 10.1016/j.tim.2017.01.005] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 01/10/2017] [Accepted: 01/20/2017] [Indexed: 12/23/2022]
Abstract
Infections caused by the bacterial pathogen Acinetobacter baumannii are a mounting concern for healthcare practitioners as widespread antibiotic resistance continues to limit therapeutic treatment options. The biological processes used by A. baumannii to cause disease are not well defined, but recent research has indicated that secreted proteins may play a major role. A variety of mechanisms have now been shown to contribute to protein secretion by A. baumannii and other pathogenic species of Acinetobacter, including a type II secretion system (T2SS), a type VI secretion system (T6SS), autotransporter, and outer membrane vesicles (OMVs). In this review, we summarize the current knowledge of secretion systems in Acinetobacter species, and highlight their unique aspects that contribute to the pathogenicity and persistence of these emerging pathogens.
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Affiliation(s)
- Brent S Weber
- Department of Molecular Microbiology, Washington University School of Medicine, St Louis, MO, USA; Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Rachel L Kinsella
- Department of Molecular Microbiology, Washington University School of Medicine, St Louis, MO, USA; Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Christian M Harding
- Department of Molecular Microbiology, Washington University School of Medicine, St Louis, MO, USA
| | - Mario F Feldman
- Department of Molecular Microbiology, Washington University School of Medicine, St Louis, MO, USA.
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Hausner J, Hartmann N, Jordan M, Büttner D. The Predicted Lytic Transglycosylase HpaH from Xanthomonas campestris pv. vesicatoria Associates with the Type III Secretion System and Promotes Effector Protein Translocation. Infect Immun 2017; 85:e00788-16. [PMID: 27895129 PMCID: PMC5278175 DOI: 10.1128/iai.00788-16] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 11/20/2016] [Indexed: 02/08/2023] Open
Abstract
The pathogenicity of the Gram-negative plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria depends on a type III secretion (T3S) system, which spans both bacterial membranes and translocates effector proteins into plant cells. The assembly of the T3S system presumably involves the predicted lytic transglycosylase (LT) HpaH, which is encoded adjacent to the T3S gene cluster. Bacterial LTs degrade peptidoglycan and often promote the formation of membrane-spanning macromolecular protein complexes. In the present study, we show that HpaH localizes to the bacterial periplasm and binds to peptidoglycan as well as to components of the T3S system, including the predicted periplasmic inner rod proteins HrpB1 and HrpB2 as well as the pilus protein HrpE. In vivo translocation assays revealed that HpaH promotes the translocation of various effector proteins and of early substrates of the T3S system, suggesting a general contribution of HpaH to type III-dependent protein export. Mutant studies and the analysis of reporter fusions showed that the N-terminal region of HpaH contributes to protein function and is proteolytically cleaved. The N-terminally truncated HpaH cleavage product is secreted into the extracellular milieu by a yet-unknown transport pathway, which is independent of the T3S system.
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Affiliation(s)
- Jens Hausner
- Institute of Biology, Genetics Department, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Nadine Hartmann
- Institute of Biology, Genetics Department, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Michael Jordan
- Institute of Biology, Genetics Department, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Daniela Büttner
- Institute of Biology, Genetics Department, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
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Abstract
Type IVa pili (T4aP) are ubiquitous microbial appendages used for adherence, twitching motility, DNA uptake, and electron transfer. Many of these functions depend on dynamic assembly and disassembly of the pilus by a megadalton-sized, cell envelope-spanning protein complex located at the poles of rod-shaped bacteria. How the T4aP assembly complex becomes integrated into the cell envelope in the absence of dedicated peptidoglycan (PG) hydrolases is unknown. After ruling out the potential involvement of housekeeping PG hydrolases in the installation of the T4aP machinery in Pseudomonas aeruginosa, we discovered that key components of inner (PilMNOP) and outer (PilQ) membrane subcomplexes are recruited to future sites of cell division. Midcell recruitment of a fluorescently tagged alignment subcomplex component, mCherry-PilO, depended on PilQ secretin monomers—specifically, their N-terminal PG-binding AMIN domains. PilP, which connects PilO to PilQ, was required for recruitment, while PilM, which is structurally similar to divisome component FtsA, was not. Recruitment preceded secretin oligomerization in the outer membrane, as loss of the PilQ pilotin PilF had no effect on localization. These results were confirmed in cells chemically blocked for cell division prior to outer membrane invagination. The hub protein FimV and a component of the polar organelle coordinator complex—PocA—were independently required for midcell recruitment of PilO and PilQ. Together, these data suggest an integrated, energy-efficient strategy for the targeting and preinstallation—rather than retrofitting—of the T4aP system into nascent poles, without the need for dedicated PG-remodeling enzymes. The peptidoglycan (PG) layer of bacterial cell envelopes has limited porosity, representing a physical barrier to the insertion of large protein complexes involved in secretion and motility. Many systems include dedicated PG hydrolase components that create space for their insertion, but the ubiquitous type IVa pilus (T4aP) system lacks such an enzyme. Instead, we found that components of the T4aP system are recruited to future sites of cell division, where they could be incorporated into the cell envelope during the formation of new poles, eliminating the need for PG hydrolases. Targeting depends on the presence of septal PG-binding motifs in specific components, as removal of those motifs causes delocalization. This preinstallation strategy for the T4aP assembly system would ensure that both daughter cells are poised to extrude pili from new poles as soon as they separate from one another.
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Abstract
Most gene clusters encoding multiprotein complexes of the bacterial cell envelope, such as conjugation and secretion systems, Type IV pili, and flagella, bear a gene encoding an enzyme with peptidoglycan hydrolase 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 localized rearrangement of the cell wall. This is assured by interaction with the structural subunits of the apparatus. Here we describe protocols to test the peptidoglycan hydrolase activity of these proteins in vitro and in solution.
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Santin YG, Cascales E. Domestication of a housekeeping transglycosylase for assembly of a Type VI secretion system. EMBO Rep 2016; 18:138-149. [PMID: 27920034 DOI: 10.15252/embr.201643206] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 10/27/2016] [Accepted: 10/28/2016] [Indexed: 01/06/2023] Open
Abstract
The type VI secretion system (T6SS) is an anti-bacterial weapon comprising a contractile tail anchored to the cell envelope by a membrane complex. The TssJ, TssL, and TssM proteins assemble a 1.7-MDa channel complex that spans the cell envelope, including the peptidoglycan layer. The electron microscopy structure of the TssJLM complex revealed that it has a diameter of ~18 nm in the periplasm, which is larger than the size of peptidoglycan pores (~2 nm), hence questioning how the T6SS membrane complex crosses the peptidoglycan layer. Here, we report that the MltE housekeeping lytic transglycosylase (LTG) is required for T6SS assembly in enteroaggregative Escherichia coli Protein-protein interaction studies further demonstrated that MltE is recruited to the periplasmic domain of TssM. In addition, we show that TssM significantly stimulates MltE activity in vitro and that MltE is required for the late stages of T6SS membrane complex assembly. Collectively, our data provide the first example of domestication and activation of a LTG encoded within the core genome for the assembly of a secretion system.
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Affiliation(s)
- Yoann G Santin
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), UMR 7255, Institut de Microbiologie de la Méditerranée, Aix-Marseille Univ - CNRS, Marseille Cedex 20, France
| | - Eric Cascales
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), UMR 7255, Institut de Microbiologie de la Méditerranée, Aix-Marseille Univ - CNRS, Marseille Cedex 20, France
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Biochemical and Structural Analysis of a Novel Esterase from Caulobacter crescentus related to Penicillin-Binding Protein (PBP). Sci Rep 2016; 6:37978. [PMID: 27905486 PMCID: PMC5131357 DOI: 10.1038/srep37978] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 11/03/2016] [Indexed: 01/16/2023] Open
Abstract
Considering that the prevalence of antibiotic-resistant pathogenic bacteria is largely increasing, a thorough understanding of penicillin-binding proteins (PBPs) is of great importance and crucial significance because this enzyme family is a main target of β-lactam-based antibiotics. In this work, combining biochemical and structural analysis, we present new findings that provide novel insights into PBPs. Here, a novel PBP homologue (CcEstA) from Caulobacter crescentus CB15 was characterized using native-PAGE, mass spectrometry, gel filtration, CD spectroscopy, fluorescence, reaction kinetics, and enzyme assays toward various substrates including nitrocefin. Furthermore, the crystal structure of CcEstA was determined at a 1.9 Å resolution. Structural analyses showed that CcEstA has two domains: a large α/β domain and a small α-helix domain. A nucleophilic serine (Ser68) residue is located in a hydrophobic groove between the two domains along with other catalytic residues (Lys71 and Try157). Two large flexible loops (UL and LL) of CcEstA are proposed to be involved in the binding of incoming substrates. In conclusion, CcEstA could be described as a paralog of the group that contains PBPs and β-lactamases. Therefore, this study could provide new structural and functional insights into the understanding this protein family.
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Genetic Dissection of the Type VI Secretion System in Acinetobacter and Identification of a Novel Peptidoglycan Hydrolase, TagX, Required for Its Biogenesis. mBio 2016; 7:mBio.01253-16. [PMID: 27729508 PMCID: PMC5061870 DOI: 10.1128/mbio.01253-16] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The type VI secretion system (T6SS) is a widespread secretory apparatus produced by Gram-negative bacteria that has emerged as a potent mediator of antibacterial activity during interbacterial interactions. Most Acinetobacter species produce a genetically conserved T6SS, although the expression and functionality of this system vary among different strains. Some pathogenic Acinetobacter baumannii strains activate this secretion system via the spontaneous loss of a plasmid carrying T6SS repressors. In this work, we compared the expression of T6SS-related genes via transcriptome sequencing and differential proteomics in cells with and without the plasmid. This approach, together with the mutational analysis of the T6SS clusters, led to the determination of the genetic components required to elaborate a functional T6SS in the nosocomial pathogen A. baumannii and the nonpathogen A. baylyi By constructing a comprehensive combination of mutants with changes in the T6SS-associated vgrG genes, we delineated their relative contributions to T6SS function. We further determined the importance of two effectors, including an effector-immunity pair, for antibacterial activity. Our genetic analysis led to the identification of an essential membrane-associated structural component named TagX, which we have characterized as a peptidoglycan hydrolase possessing l,d-endopeptidase activity. TagX shows homology to known bacteriophage l,d-endopeptidases and is conserved in the T6SS clusters of several bacterial species. We propose that TagX is the first identified enzyme that fulfills the important role of enabling the transit of T6SS machinery across the peptidoglycan layer of the T6SS-producing bacterium. IMPORTANCE Acinetobacter baumannii is one of the most troublesome and least investigated multidrug-resistant bacterial pathogens. We have previously shown that A. baumannii employs a T6SS to eliminate competing bacteria. Here we provide a comprehensive analysis of the components of the T6SS of Acinetobacter, and our results provide genetic and functional insights into the Acinetobacter T6SS. Through this analysis, we identified a novel peptidoglycan hydrolase, TagX, that is required for biogenesis of the T6SS apparatus. This is the first peptidoglycanase specialized in T6SS function identified in any species. We propose that this enzyme is required for the spatially and temporally regulated digestion of peptidoglycan to allow assembly of the T6SS machinery.
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Domínguez-Gil T, Lee M, Acebrón-Avalos I, Mahasenan KV, Hesek D, Dik DA, Byun B, Lastochkin E, Fisher JF, Mobashery S, Hermoso JA. Activation by Allostery in Cell-Wall Remodeling by a Modular Membrane-Bound Lytic Transglycosylase from Pseudomonas aeruginosa. Structure 2016; 24:1729-1741. [PMID: 27618662 DOI: 10.1016/j.str.2016.07.019] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 07/24/2016] [Accepted: 07/26/2016] [Indexed: 11/19/2022]
Abstract
Bacteria grow and divide without loss of cellular integrity. This accomplishment is notable, as a key component of their cell envelope is a surrounding glycopeptide polymer. In Gram-negative bacteria this polymer-the peptidoglycan-grows by the difference between concurrent synthesis and degradation. The regulation of the enzymatic ensemble for these activities is poorly understood. We report herein the structural basis for the control of one such enzyme, the lytic transglycosylase MltF of Pseudomonas aeruginosa. Its structure comprises two modules: an ABC-transporter-like regulatory module and a catalytic module. Occupancy of the regulatory module by peptidoglycan-derived muropeptides effects a dramatic and long-distance (40 Å) conformational change, occurring over the entire protein structure, to open its active site for catalysis. This discovery of the molecular basis for the allosteric control of MltF catalysis is foundational to further study of MltF within the complex enzymatic orchestration of the dynamic peptidoglycan.
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Affiliation(s)
- Teresa Domínguez-Gil
- Departamento de Cristalografía y Biología Estructural, Instituto de Química-Física "Rocasolano", CSIC, Serrano 119, 28006 Madrid, Spain
| | - Mijoon Lee
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Iván Acebrón-Avalos
- Departamento de Cristalografía y Biología Estructural, Instituto de Química-Física "Rocasolano", CSIC, Serrano 119, 28006 Madrid, Spain
| | - Kiran V Mahasenan
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Dusan Hesek
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - David A Dik
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Byungjin Byun
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Elena Lastochkin
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Jed F Fisher
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
| | - Juan A Hermoso
- Departamento de Cristalografía y Biología Estructural, Instituto de Química-Física "Rocasolano", CSIC, Serrano 119, 28006 Madrid, Spain.
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Abstract
Lactic acid bacteria (LAB) are important starter, commensal, or pathogenic microorganisms. The stress physiology of LAB has been studied in depth for over 2 decades, fueled mostly by the technological implications of LAB robustness in the food industry. Survival of probiotic LAB in the host and the potential relatedness of LAB virulence to their stress resilience have intensified interest in the field. Thus, a wealth of information concerning stress responses exists today for strains as diverse as starter (e.g., Lactococcus lactis), probiotic (e.g., several Lactobacillus spp.), and pathogenic (e.g., Enterococcus and Streptococcus spp.) LAB. Here we present the state of the art for LAB stress behavior. We describe the multitude of stresses that LAB are confronted with, and we present the experimental context used to study the stress responses of LAB, focusing on adaptation, habituation, and cross-protection as well as on self-induced multistress resistance in stationary phase, biofilms, and dormancy. We also consider stress responses at the population and single-cell levels. Subsequently, we concentrate on the stress defense mechanisms that have been reported to date, grouping them according to their direct participation in preserving cell energy, defending macromolecules, and protecting the cell envelope. Stress-induced responses of probiotic LAB and commensal/pathogenic LAB are highlighted separately due to the complexity of the peculiar multistress conditions to which these bacteria are subjected in their hosts. Induction of prophages under environmental stresses is then discussed. Finally, we present systems-based strategies to characterize the "stressome" of LAB and to engineer new food-related and probiotic LAB with improved stress tolerance.
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Abstract
Extracellular vesicles (EVs) are produced by virtually all cell types. Within the past few years, work in this field has revealed more information about fungal EVs. Fungal EVs have been shown to carry proteins, lipids, pigments, polysaccharides, and RNA; these components are known virulence factors, a fact which supports the hypothesis that fungal EVs concentrate pathogenic determinants. Additionally, recent studies have demonstrated that fungal EVs stimulate the host immune system. In this review, putative roles of fungal EVs are discussed, including their potential as vaccination tools and their possible contribution to pathogenesis in invasive fungal diseases.
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The Composition of the Cell Envelope Affects Conjugation in Bacillus subtilis. J Bacteriol 2016; 198:1241-9. [PMID: 26833415 DOI: 10.1128/jb.01044-15] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2016] [Accepted: 01/27/2016] [Indexed: 01/13/2023] Open
Abstract
UNLABELLED Conjugation in bacteria is the contact-dependent transfer of DNA from one cell to another via donor-encoded conjugation machinery. It is a major type of horizontal gene transfer between bacteria. Conjugation of the integrative and conjugative element ICEBs1 into Bacillus subtilis is affected by the composition of phospholipids in the cell membranes of the donor and recipient. We found that reduction (or elimination) of lysyl-phosphatidylglycerol caused by loss of mpr F caused a decrease in conjugation efficiency. Conversely, alterations that caused an increase in lysyl-phosphatidylglycerol, including loss of ugtP or overproduction of mprF, caused an increase in conjugation efficiency. In addition, we found that mutations that alter production of other phospholipids, e.g., loss of clsA and yfnI, also affected conjugation, apparently without substantively altering levels of lysyl-phosphatidylglycerol, indicating that there are multiple pathways by which changes to the cell envelope affect conjugation. We found that the contribution of mprF to conjugation was affected by the chemical environment. Wild-type cells were generally more responsive to addition of anions that enhanced conjugation, whereas mprF mutant cells were more sensitive to combinations of anions that inhibited conjugation at pH 7. Our results indicate that mprF and lysyl-phosphatidylglycerol allow cells to maintain relatively consistent conjugation efficiencies under a variety of ionic conditions. IMPORTANCE Horizontal gene transfer is a driving force in microbial evolution, enabling cells that receive DNA to acquire new genes and phenotypes. Conjugation, the contact-dependent transfer of DNA from a donor to a recipient by a donor-encoded secretion machine, is a prevalent type of horizontal gene transfer. Although critically important, it is not well understood how the recipient influences the success of conjugation. We found that the composition of phospholipids in the membranes of donors and recipients influences the success of transfer of the integrative and conjugative element ICEBs1 in Bacillus subtilis Specifically, the presence of lysyl-phosphatidylglycerol enables relatively constant conjugation efficiencies in a range of diverse chemical environments.
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Sandoz KM, Popham DL, Beare PA, Sturdevant DE, Hansen B, Nair V, Heinzen RA. Transcriptional Profiling of Coxiella burnetii Reveals Extensive Cell Wall Remodeling in the Small Cell Variant Developmental Form. PLoS One 2016; 11:e0149957. [PMID: 26909555 PMCID: PMC4766238 DOI: 10.1371/journal.pone.0149957] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 02/05/2016] [Indexed: 11/19/2022] Open
Abstract
A hallmark of Coxiella burnetii, the bacterial cause of human Q fever, is a biphasic developmental cycle that generates biologically, ultrastructurally, and compositionally distinct large cell variant (LCV) and small cell variant (SCV) forms. LCVs are replicating, exponential phase forms while SCVs are non-replicating, stationary phase forms. The SCV has several properties, such as a condensed nucleoid and an unusual cell envelope, suspected of conferring enhanced environmental stability. To identify genetic determinants of the LCV to SCV transition, we profiled the C. burnetii transcriptome at 3 (early LCV), 5 (late LCV), 7 (intermediate forms), 14 (early SCV), and 21 days (late SCV) post-infection of Vero epithelial cells. Relative to early LCV, genes downregulated in the SCV were primarily involved in intermediary metabolism. Upregulated SCV genes included those involved in oxidative stress responses, arginine acquisition, and cell wall remodeling. A striking transcriptional signature of the SCV was induction (>7-fold) of five genes encoding predicted L,D transpeptidases that catalyze nonclassical 3-3 peptide cross-links in peptidoglycan (PG), a modification that can influence several biological traits in bacteria. Accordingly, of cross-links identified, muropeptide analysis showed PG of SCV with 46% 3-3 cross-links as opposed to 16% 3-3 cross-links for LCV. Moreover, electron microscopy revealed SCV with an unusually dense cell wall/outer membrane complex as compared to LCV with its clearly distinguishable periplasm and inner and outer membranes. Collectively, these results indicate the SCV produces a unique transcriptome with a major component directed towards remodeling a PG layer that likely contributes to Coxiella's environmental resistance.
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Affiliation(s)
- Kelsi M. Sandoz
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - David L. Popham
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Paul A. Beare
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Daniel E. Sturdevant
- Genomics Unit, Research Technologies Branch, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Bryan Hansen
- Electron Microscopy Unit, Research Technologies Branch, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Vinod Nair
- Electron Microscopy Unit, Research Technologies Branch, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Robert A. Heinzen
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
- * E-mail:
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Roces C, Rodríguez A, Martínez B. Cell Wall-active Bacteriocins and Their Applications Beyond Antibiotic Activity. Probiotics Antimicrob Proteins 2016; 4:259-72. [PMID: 26782186 DOI: 10.1007/s12602-012-9116-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Microorganisms synthesize several compounds with antimicrobial activity in order to compete or defend themselves against others and ensure their survival. In this line, the cell wall is a major protective barrier whose integrity is essential for many vital bacterial processes. Probably for this reason, it represents a 'hot spot' as a target for many antibiotics and antimicrobial peptides such as bacteriocins. Bacteriocins have largely been recognized by their pore-forming ability that collapses the selective permeability of the cytoplasmic membrane. However, in the last few years, many bacteriocins have been shown to inhibit cell wall biosyntheis alone, or in a concerted action with pore formation like nisin. Examples of cell wall-active bacteriocins are found in both Gram-negative and Gram-positive bacteria and include a wide diversity of structures such as nisin-like and mersacidin-like lipid II-binding bacteriocins, two-peptide lantibiotics, and non-modified bacteriocins. In this review, we summarize the current knowledge on these antimicrobial peptides as well as the role, composition, and biosynthesis of the bacterial cell wall as their target. Moreover, even though bacteriocins have been a matter of interest as natural food antimicrobials, we propose them as suitable tools to provide new means to improve biotechnologically relevant microorganisms.
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Affiliation(s)
- Clara Roces
- DairySafe Group, Department of Technology and Biotechnology of Dairy Products, Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Paseo Río Linares s/n., 33300, Villaviciosa, Asturias, Spain
| | - Ana Rodríguez
- DairySafe Group, Department of Technology and Biotechnology of Dairy Products, Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Paseo Río Linares s/n., 33300, Villaviciosa, Asturias, Spain
| | - Beatriz Martínez
- DairySafe Group, Department of Technology and Biotechnology of Dairy Products, Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Paseo Río Linares s/n., 33300, Villaviciosa, Asturias, Spain.
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