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Portela R, A. Faria N, Mwangi M, Miragaia M, de Lencastre H, Tomasz A, Gonçalves Sobral R. Analysis of a Cell Wall Mutant Highlights Rho-Dependent Genome Amplification Events in Staphylococcus aureus. Microbiol Spectr 2022; 10:e0248321. [PMID: 36094182 PMCID: PMC9603463 DOI: 10.1128/spectrum.02483-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 08/06/2022] [Indexed: 01/04/2023] Open
Abstract
In a study of antibiotic resistance in Staphylococcus aureus, specific cell wall mutants were previously generated for the peptidoglycan biosynthesis gene murF, by the insertion of an integrative plasmid. A collection of 30 independent mutants was obtained, and all harbored a variable number of copies of the inserted plasmid, arranged in tandem in the chromosome. Of the 30 mutants, only 3, F9, F20 and F26, with a lower number of plasmid copies, showed an altered peptidoglycan structure, lower resistance to β-lactams and a different loss-of-function mutation in rho gene, that encodes a transcription termination factor. The rho mutations were found to correlate with the level of oxacillin resistance, since genetic complementation with rho gene reestablished the resistance and cell wall parental profile in F9, F20 and F26 strains. Furthermore, complementation with rho resulted in the amplification of the number of plasmid tandem repeats, suggesting that Rho enabled events of recombination that favored a rearrangement in the chromosome in the region of the impaired murF gene. Although the full mechanism of reversion of the cell wall damage was not fully elucidated, we showed that Rho is involved in the recombination process that mediates the tandem amplification of exogeneous DNA fragments inserted into the chromosome. IMPORTANCE The cell wall of bacteria, namely, peptidoglycan, is the target of several antibiotic classes such as β-lactams. Staphylococcus aureus is well known for its capacity to adapt to antibiotic stress and develop resistance strategies, namely, to β-lactams. In this context, the construction of cell wall mutants provides useful models to study the development of such resistance mechanisms. Here, we characterized a collection of independent mutants, impaired in the same peptidoglycan biosynthetic step, obtained through the insertion of a plasmid in the coding region of murF gene. S. aureus demonstrated the capacity to overcome the cell wall damage by amplifying the copy number of the inserted plasmid, through an undescribed mechanism that involves the Rho transcription termination factor.
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Affiliation(s)
- Raquel Portela
- Associate Laboratory i4HB - Institute for Health and Bioeconomy, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
- Laboratory of Molecular Microbiology of Bacterial Pathogens, UCIBIO – Applied Molecular Biosciences Unit, Department of Life Sciences, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Nuno A. Faria
- Laboratory of Bacterial Evolution and Molecular Epidemiology, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB NOVA), Oeiras, Portugal
| | - Michael Mwangi
- Laboratory of Microbiology and Infectious Diseases, The Rockefeller University, New York, New York, USA
| | - Maria Miragaia
- Laboratory of Bacterial Evolution and Molecular Epidemiology, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB NOVA), Oeiras, Portugal
| | - Hermínia de Lencastre
- Laboratory of Microbiology and Infectious Diseases, The Rockefeller University, New York, New York, USA
- Laboratory of Molecular Genetics, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB NOVA), Oeiras, Portugal
| | - Alexander Tomasz
- Laboratory of Microbiology and Infectious Diseases, The Rockefeller University, New York, New York, USA
| | - Rita Gonçalves Sobral
- Associate Laboratory i4HB - Institute for Health and Bioeconomy, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
- Laboratory of Molecular Microbiology of Bacterial Pathogens, UCIBIO – Applied Molecular Biosciences Unit, Department of Life Sciences, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
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Shi M, Willing SE, Kim HK, Schneewind O, Missiakas D. Peptidoglycan Contribution to the B Cell Superantigen Activity of Staphylococcal Protein A. mBio 2021; 12:e00039-21. [PMID: 33879590 PMCID: PMC8092194 DOI: 10.1128/mbio.00039-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Accepted: 03/17/2021] [Indexed: 11/20/2022] Open
Abstract
Staphylococcus aureus causes reiterative and chronic persistent infections. This can be explained by the formidable ability of this pathogen to escape immune surveillance mechanisms. Cells of S. aureus display the abundant staphylococcal protein A (SpA). SpA binds to immunoglobulin (Ig) molecules and coats the bacterial surface to prevent phagocytic uptake. SpA also binds and cross-links variable heavy 3 (VH3) idiotype (IgM) B cell receptors, promoting B cell expansion and the secretion of nonspecific VH3-IgM via a mechanism requiring CD4+ T cell help. SpA binding to antibodies is mediated by the N-terminal Ig-binding domains (IgBDs). The so-called region X, uncharacterized LysM domain, and C-terminal LPXTG sorting signal for peptidoglycan attachment complete the linear structure of the protein. Here, we report that both the LysM domain and the LPXTG motif sorting signal are required for the B cell superantigen activity of SpA in a mouse model of infection. SpA molecules purified from staphylococcal cultures are sufficient to exert B cell superantigen activity and promote immunoglobulin secretion as long as they carry intact LysM and LPXTG motif domains with bound peptidoglycan fragments. The LysM domain binds the glycan chains of peptidoglycan fragments, whereas the LPXTG motif is covalently linked to wall peptides lacking glycan. These findings emphasize the complexity of SpA interactions with B cell receptors.IMPORTANCE The LysM domain is found in all kingdoms of life. While their function in mammals is not known, LysM domains of bacteria and their phage parasites are associated with enzymes that cleave or remodel peptidoglycan. Plants recognize microbe-associated molecular patterns such as chitin via receptors endowed with LysM-containing ectodomains. In plants, such receptors play equally important roles in defense and symbiosis signaling. SpA of S. aureus carries a LysM domain that binds glycan strands of peptidoglycan to influence defined B cell responses that divert pathogen-specific adaptive immune responses.
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Affiliation(s)
- Miaomiao Shi
- Howard Taylor Ricketts Laboratory, Argonne National Laboratory, Lemont, Illinois, USA
| | | | - Hwan Keun Kim
- Department of Microbiology, University of Chicago, Chicago, Illinois, USA
| | - Olaf Schneewind
- Department of Microbiology, University of Chicago, Chicago, Illinois, USA
| | - Dominique Missiakas
- Howard Taylor Ricketts Laboratory, Argonne National Laboratory, Lemont, Illinois, USA
- Department of Microbiology, University of Chicago, Chicago, Illinois, USA
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Fisher JF, Mobashery S. β-Lactams against the Fortress of the Gram-Positive Staphylococcus aureus Bacterium. Chem Rev 2021; 121:3412-3463. [PMID: 33373523 PMCID: PMC8653850 DOI: 10.1021/acs.chemrev.0c01010] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The biological diversity of the unicellular bacteria-whether assessed by shape, food, metabolism, or ecological niche-surely rivals (if not exceeds) that of the multicellular eukaryotes. The relationship between bacteria whose ecological niche is the eukaryote, and the eukaryote, is often symbiosis or stasis. Some bacteria, however, seek advantage in this relationship. One of the most successful-to the disadvantage of the eukaryote-is the small (less than 1 μm diameter) and nearly spherical Staphylococcus aureus bacterium. For decades, successful clinical control of its infection has been accomplished using β-lactam antibiotics such as the penicillins and the cephalosporins. Over these same decades S. aureus has perfected resistance mechanisms against these antibiotics, which are then countered by new generations of β-lactam structure. This review addresses the current breadth of biochemical and microbiological efforts to preserve the future of the β-lactam antibiotics through a better understanding of how S. aureus protects the enzyme targets of the β-lactams, the penicillin-binding proteins. The penicillin-binding proteins are essential enzyme catalysts for the biosynthesis of the cell wall, and understanding how this cell wall is integrated into the protective cell envelope of the bacterium may identify new antibacterials and new adjuvants that preserve the efficacy of the β-lactams.
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Affiliation(s)
- Jed F Fisher
- Department of Chemistry and Biochemistry, McCourtney Hall, University of Notre Dame, Notre Dame Indiana 46556, United States
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry, McCourtney Hall, University of Notre Dame, Notre Dame Indiana 46556, United States
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New insights in the coordinated amidase and glucosaminidase activity of the major autolysin (Atl) in Staphylococcus aureus. Commun Biol 2020; 3:695. [PMID: 33219282 PMCID: PMC7679415 DOI: 10.1038/s42003-020-01405-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 10/15/2020] [Indexed: 11/17/2022] Open
Abstract
After bacterial cell division, the daughter cells are still covalently interlinked by the peptidoglycan network which is resolved by specific hydrolases (autolysins) to release the daughter cells. In staphylococci, the major autolysin (Atl) with its two domain enzymes, N-acetylmuramyl-L-alanine amidase (AmiA) and β-N-acetylglucosaminidase (GlcA), resolves the peptidoglycan to release the daughter cells. Internal deletions in each of the enzyme domains revealed defined morphological alterations such as cell cluster formation in ΔamiA, ΔglcA and Δatl, and asymmetric cell division in the ΔglcA. A most important finding was that GlcA activity requires the prior removal of the stem peptide by AmiA for its activity thus the naked glycan strand is its substrate. Furthermore, GlcA is not an endo-β-N-acetylglucosaminidase but an exo-enzyme that cuts the glycan backbone to disaccharides independent of its O-acetylation modification. Our results shed new light into the sequential peptidoglycan hydrolysis by AmiA and GlcA during cell division in staphylococci. Nega et al. shed light on the interplay of the two domain enzymes of the major autolysin, AmiA and GlcA, in S. aureus for peptidoglycan hydrolysis during bacterial cell division. They show that GlcA requires the prior removal of the stem peptide by AmiA for its activity and that GlcA is not an endo-enzyme as previously thought, but an exo-enzyme that chops down the glycan backbone to disaccharides independent of its O-acetylation modification.
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Abstract
Dating back to the 1960s, initial studies on the staphylococcal cell wall were driven by the need to clarify the mode of action of the first antibiotics and the resistance mechanisms developed by the bacteria. During the following decades, the elucidation of the biosynthetic path and primary composition of staphylococcal cell walls was propelled by advances in microbial cell biology, specifically, the introduction of high-resolution analytical techniques and molecular genetic approaches. The field of staphylococcal cell wall gradually gained its own significance as the complexity of its chemical structure and involvement in numerous cellular processes became evident, namely its versatile role in host interactions, coordination of cell division and environmental stress signaling.This chapter includes an updated description of the anatomy of staphylococcal cell walls, paying particular attention to information from the last decade, under four headings: high-resolution analysis of the Staphylococcus aureus peptidoglycan; variations in peptidoglycan composition; genetic determinants and enzymes in cell wall synthesis; and complex functions of cell walls. The latest contributions to a more precise picture of the staphylococcal cell envelope were possible due to recently developed state-of-the-art microscopy and spectroscopy techniques and to a wide combination of -omics approaches, that are allowing to obtain a more integrative view of this highly dynamic structure.
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Role of MurT C-Terminal Domain in the Amidation of Staphylococcus aureus Peptidoglycan. Antimicrob Agents Chemother 2019; 63:AAC.00957-19. [PMID: 31358586 DOI: 10.1128/aac.00957-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 07/20/2019] [Indexed: 11/20/2022] Open
Abstract
Glutamate amidation, a secondary modification of the peptidoglycan, was first identified in Staphylococcus aureus It is catalyzed by the protein products of the murT and gatD genes, which are conserved and colocalized in the genomes of most sequenced Gram-positive bacterial species. The MurT-GatD complex is required for cell viability, full resistance to β-lactam antibiotics, and resistance to human lysozyme and is recognized as an attractive target for new antimicrobials. Great effort has been invested in the study of this step, culminating recently in three independent reports addressing the structural elucidation of the MurT-GatD complex. In this work, we demonstrate through the use of nonstructural approaches the critical and multiple roles of the C-terminal domain of MurT, annotated as DUF1727, in the MurT-GatD enzymatic complex. This domain provides the physical link between the two enzymatic activities and is essential for the amidation reaction. Copurification of recombinant MurT and GatD proteins and bacterial two-hybrid assays support the observation that the MurT-GatD interaction occurs through this domain. Most importantly, we provide in vivo evidence of the effect of substitutions at specific residues in DUF1727 on cell wall peptidoglycan amidation and on the phenotypes of oxacillin resistance and bacterial growth.
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Reichert S, Ebner P, Bonetti EJ, Luqman A, Nega M, Schrenzel J, Spröer C, Bunk B, Overmann J, Sass P, François P, Götz F. Genetic Adaptation of a Mevalonate Pathway Deficient Mutant in Staphylococcus aureus. Front Microbiol 2018; 9:1539. [PMID: 30050520 PMCID: PMC6052127 DOI: 10.3389/fmicb.2018.01539] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 06/20/2018] [Indexed: 01/21/2023] Open
Abstract
In this study we addressed the question how a mevalonate (MVA)-auxotrophic Staphylococcus aureusΔmvaS mutant can revert to prototrophy. This mutant couldn't grow in the absence of MVA. However, after a long lag-phase of 4-6 days the mutant adapted from auxotrophic to prototrophic phenotype. During that time, it acquired two point mutations: One mutation in the coding region of the regulator gene spx, which resulted in an amino acid exchange that decreased Spx function. The other mutation in the upstream-element within the core-promoter of the mevalonolactone lactonase gene drp35. This mutation led to an increased expression of drp35. In repeated experiments the mutations always occurred in spx and drp35 and in the same order. The first detectable mutation appeared in spx and allowed slight growth; the second mutation, in drp35, increased growth further. Phenotypical characterizations of the mutant showed that small amounts of the lipid-carrier undecaprenol are synthesized, despite the lack of mvaS. The growth of the adapted clone, ΔmvaSad, indicates that the mutations reawake a rescue bypass. We think that this bypass enters the MVA pathway at the stage of MVA, because blocking the pathway downstream of MVA led to growth arrest of the mutant. In addition, the lactonase Drp35 is able to convert mevalonolactone to MVA. Summarized, we describe here a mutation-based two-step adaptation process that allows resuscitation of growth of the ΔmvaS mutant.
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Affiliation(s)
- Sebastian Reichert
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
| | - Patrick Ebner
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
| | - Eve-Julie Bonetti
- Genomic Research Laboratory, Division of Infectious Diseases, Geneva University Hospital, Geneva, Switzerland
| | - Arif Luqman
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
| | - Mulugeta Nega
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
| | - Jacques Schrenzel
- Genomic Research Laboratory, Division of Infectious Diseases, Geneva University Hospital, Geneva, Switzerland
| | - Cathrin Spröer
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Boyke Bunk
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Jörg Overmann
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Peter Sass
- Microbial Bioactive Compounds, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
| | - Patrice François
- Genomic Research Laboratory, Division of Infectious Diseases, Geneva University Hospital, Geneva, Switzerland
| | - Friedrich Götz
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
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Antibiotic Resistance as a Stress Response: Recovery of High-Level Oxacillin Resistance in Methicillin-Resistant Staphylococcus aureus "Auxiliary" ( fem) Mutants by Induction of the Stringent Stress Response. Antimicrob Agents Chemother 2017. [PMID: 28630179 DOI: 10.1128/aac.00313-17] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Studies with methicillin-resistant Staphylococcus aureus (MRSA) strain COL have shown that the optimal resistance phenotype requires not only mecA but also a large number of "auxiliary genes" identified by Tn551 mutagenesis. The majority of auxiliary mutants showed greatly increased levels of oxacillin resistance when grown in the presence of sub-MICs of mupirocin, suggesting that the mechanism of reduced resistance in the auxiliary mutants involved the interruption of a stringent stress response, causing reduced production of penicillin-binding protein 2A (PBP 2A).
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Morales Angeles D, Liu Y, Hartman AM, Borisova M, de Sousa Borges A, de Kok N, Beilharz K, Veening JW, Mayer C, Hirsch AKH, Scheffers DJ. Pentapeptide-rich peptidoglycan at the Bacillus subtilis cell-division site. Mol Microbiol 2017; 104:319-333. [PMID: 28118510 DOI: 10.1111/mmi.13629] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/18/2017] [Indexed: 11/28/2022]
Abstract
Peptidoglycan (PG), the major component of the bacterial cell wall, is one large macromolecule. To allow for the different curvatures of PG at cell poles and division sites, there must be local differences in PG architecture and eventually also chemistry. Here we report such local differences in the Gram-positive rod-shaped model organism Bacillus subtilis. Single-cell analysis after antibiotic treatment and labeling of the cell wall with a fluorescent analogue of vancomycin or the fluorescent D-amino acid analogue (FDAA) HCC-amino-D-alanine revealed that PG at the septum contains muropeptides with unprocessed stem peptides (pentapeptides). Whereas these pentapeptides are normally shortened after incorporation into PG, this activity is reduced at division sites indicating either a lower local degree of PG crosslinking or a difference in PG composition, which could be a topological marker for other proteins. The pentapeptides remain partially unprocessed after division when they form the new pole of a cell. The accumulation of unprocessed PG at the division site is not caused by the activity of the cell division specific penicillin-binding protein 2B. To our knowledge, this is the first indication of local differences in the chemical composition of PG in Gram-positive bacteria.
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Affiliation(s)
- Danae Morales Angeles
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute University of Groningen, The Netherlands
| | - Yun Liu
- Stratingh Institute for Chemistry, University of Groningen, The Netherlands
| | - Alwin M Hartman
- Stratingh Institute for Chemistry, University of Groningen, The Netherlands
| | - Marina Borisova
- Department of Biology, Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
| | - Anabela de Sousa Borges
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute University of Groningen, The Netherlands
| | - Niels de Kok
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute University of Groningen, The Netherlands
| | - Katrin Beilharz
- Molecular Genetics Group, Groningen Biomolecular Sciences and Biotechnology Institute, Centre for Synthetic Biology, University of Groningen, The Netherlands
| | - Jan-Willem Veening
- Molecular Genetics Group, Groningen Biomolecular Sciences and Biotechnology Institute, Centre for Synthetic Biology, University of Groningen, The Netherlands.,Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Biophore Building, Lausanne, CH-1015, Switzerland
| | - Christoph Mayer
- Department of Biology, Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
| | - Anna K H Hirsch
- Stratingh Institute for Chemistry, University of Groningen, The Netherlands
| | - Dirk-Jan Scheffers
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute University of Groningen, The Netherlands
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The Peptidoglycan Pattern of Staphylococcus carnosus TM300-Detailed Analysis and Variations Due to Genetic and Metabolic Influences. Antibiotics (Basel) 2016; 5:antibiotics5040033. [PMID: 27669322 PMCID: PMC5187514 DOI: 10.3390/antibiotics5040033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 08/09/2016] [Accepted: 09/02/2016] [Indexed: 11/17/2022] Open
Abstract
The Gram-positive bacterium Staphylococcus carnosus (S. carnosus) TM300 is an apathogenic staphylococcal species commonly used in meat starter cultures. As with all Gram-positive bacteria, its cytoplasmic membrane is surrounded by a thick peptidoglycan (PGN) or murein sacculus consisting of several layers of glycan strands cross-linked by peptides. In contrast to pathogenic staphylococci, mainly Staphylococcus aureus (S. aureus), the chemical composition of S. carnosus PGN is not well studied so far. UPLC/MS analysis of enzymatically digested S. carnosus TM300 PGN revealed substantial differences in its composition compared to the known pattern of S. aureus. While in S. aureus the uncross-linked stem peptide consists of a pentapeptide, in S. carnosus, this part of the PGN is shortened to tripeptides. Furthermore, we found the PGN composition to vary when cells were incubated under certain conditions. The collective overproduction of HlyD, FtsE and FtsX—a putative protein complex interacting with penicillin-binding protein 2 (PBP2)—caused the reappearance of classical penta stem peptides. In addition, under high sugar conditions, tetra stem peptides occur due to overflow metabolism. This indicates that S. carnosus TM300 cells adapt to various conditions by modification of their PGN.
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Role of the Stringent Stress Response in the Antibiotic Resistance Phenotype of Methicillin-Resistant Staphylococcus aureus. Antimicrob Agents Chemother 2016; 60:2311-7. [PMID: 26833147 DOI: 10.1128/aac.02697-15] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Accepted: 01/25/2016] [Indexed: 01/03/2023] Open
Abstract
Resistance to beta-lactam antibiotics in methicillin-resistantStaphylococcus aureus(MRSA) requires the presence of an acquired genetic determinant,mecAormecC, which encode penicillin-binding protein PBP2A or PBP2A', respectively. Although all MRSA strains share a mechanism of resistance, the phenotypic expression of beta-lactam resistance shows considerable strain-to-strain variation. The stringent stress response, a stress response that results from nutrient limitation, was shown to play a key role in determining the resistance level of an MRSA strain. In the present study, we validated the impact of the stringent stress response on transcription and translation ofmecAin the MRSA clinical isolate strain N315, which also carries known regulatory genes (mecI/mecR1/mecR2andblaI/blaR1) formecAtranscription. We showed that the impact of the stringent stress response on the resistance level may be restricted to beta-lactam resistance based on a "foreign" determinant such asmecA, as opposed to resistance based on mutations in the nativeS. aureusdeterminantpbpB(encoding PBP2). Our observations demonstrate that high-level resistance mediated by the stringent stress response follows the current model of beta-lactam resistance in which the native PBP2 protein is also essential for expression of the resistance phenotype. We also show that theStaphylococcus sciuri pbpDgene (also calledmecAI), the putative evolutionary precursor ofmecA, confers oxacillin resistance in anS. aureusstrain, generating a heterogeneous phenotype that can be converted to high and homogenous resistance by induction of the stringent stress response in the bacteria.
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Jacquier N, Frandi A, Viollier PH, Greub G. Disassembly of a Medial Transenvelope Structure by Antibiotics during Intracellular Division. ACTA ACUST UNITED AC 2015; 22:1217-27. [PMID: 26364930 DOI: 10.1016/j.chembiol.2015.08.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 07/28/2015] [Accepted: 08/01/2015] [Indexed: 10/23/2022]
Abstract
Chlamydiales possess a minimal but functional peptidoglycan precursor biosynthetic and remodeling pathway involved in the assembly of the division septum by an atypical cytokinetic machine and cryptic or modified peptidoglycan-like structure (PGLS). How this reduced cytokinetic machine collectively coordinates the invagination of the envelope has not yet been explored in Chlamydiales. In other Gram-negative bacteria, peptidoglycan provides anchor points that connect the outer membrane to the peptidoglycan during constriction using the Pal-Tol complex. Purifying PGLS and associated proteins from the chlamydial pathogen Waddlia chondrophila, we unearthed the Pal protein as a peptidoglycan-binding protein that localizes to the chlamydial division septum along with other components of the Pal-Tol complex. Together, our PGLS characterization and peptidoglycan-binding assays support the notion that diaminopimelic acid is an important determinant recruiting Pal to the division plane to coordinate the invagination of all envelope layers with the conserved Pal-Tol complex, even during osmotically protected intracellular growth.
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Affiliation(s)
- Nicolas Jacquier
- Department of Laboratories, Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne 1011, Switzerland
| | - Antonio Frandi
- Department of Microbiology & Molecular Medicine, Institute of Genetics & Genomics in Geneva (iGE3), Faculty of Medicine/CMU, University of Geneva, Geneva 1211, Switzerland
| | - Patrick H Viollier
- Department of Microbiology & Molecular Medicine, Institute of Genetics & Genomics in Geneva (iGE3), Faculty of Medicine/CMU, University of Geneva, Geneva 1211, Switzerland.
| | - Gilbert Greub
- Department of Laboratories, Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne 1011, Switzerland.
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Gautam S, Kim T, Spiegel DA. Chemical probes reveal an extraseptal mode of cross-linking in Staphylococcus aureus. J Am Chem Soc 2015; 137:7441-7. [PMID: 26035224 DOI: 10.1021/jacs.5b02972] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Staphylococcus aureus is an important human pathogen and a model organism for studying cell wall synthesis in Gram-positive cocci. The prevailing model of cell wall biogenesis in cocci holds that peptidoglycan synthesis (i.e., transglycosylation and cross-linking) is restricted spatially to the septal cross-wall and temporally to cell division. Previously, we developed a method for visualizing cross-linking in S. aureus using fluorescently tagged mimics of the endogenous substrate of penicillin-binding proteins (PBPs). These probes are incorporated into the cell wall of S. aureus specifically by PBP4, allowing localization of the enzyme's cross-linking activity in vivo with precise spatial and temporal resolution. Here, using this methodology, we have discovered that PBP4 is active not only at the septum, but unexpectedly at the peripheral wall as well. These results challenge the long-held belief that peptidoglycan synthesis is restricted to the septum in spherical bacteria, and instead indicate the presence of two spatiotemporally distinct modes of cross-linking in S. aureus: one at the septum during cell division, and another at the peripheral wall between divisions.
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Affiliation(s)
- Samir Gautam
- §Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06511, United States
| | - Taehan Kim
- §Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06511, United States
| | - David A Spiegel
- §Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06511, United States
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From cells to muropeptide structures in 24 h: peptidoglycan mapping by UPLC-MS. Sci Rep 2014; 4:7494. [PMID: 25510564 PMCID: PMC4267204 DOI: 10.1038/srep07494] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 11/19/2014] [Indexed: 11/15/2022] Open
Abstract
Peptidoglycan (PGN) is ubiquitous in nearly all bacterial species. The PGN sacculus protects the cells against their own internal turgor making PGN one of the most important targets for antibacterial treatment. Within the last sixty years PGN composition has been intensively studied by various methods. The breakthrough was the application of HPLC technology on the analysis of muropeptides. However, preparation of pure PGN relied on a very time consuming method of about one week. We established a purification protocol for both Gram-positive and Gram-negative bacteria which can be completely performed in plastic reaction tubes yielding pure muropeptides within 24 hours. The muropeptides can be analyzed by UPLC-MS, allowing their immediate determination. This new rapid method provides the feasibility to screen PGN composition even in high throughput, making it a highly useful tool for basic research as well as for the pharmaceutical industry.
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Carvalhais V, França A, Pier GB, Vilanova M, Cerca N, Vitorino R. Comparative proteomic and transcriptomic profile of Staphylococcus epidermidis biofilms grown in glucose-enriched medium. Talanta 2014; 132:705-12. [PMID: 25476368 DOI: 10.1016/j.talanta.2014.10.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2014] [Revised: 10/01/2014] [Accepted: 10/08/2014] [Indexed: 01/07/2023]
Abstract
Staphylococcus epidermidis is an important nosocomial agent among carriers of indwelling medical devices, due to its strong ability to form biofilms on inert surfaces. Contrary to some advances made in the transcriptomic field, proteome characterization of S. epidermidis biofilms is less developed. To highlight the relation between transcripts and proteins of S. epidermidis biofilms, we analyzed the proteomic profile obtained by two mechanical lysis methods (sonication and bead beating), associated with two distinct detergent extraction buffers, namely SDS and CHAPS. Based on gel electrophoresis-LC-MS/MS, we identified a total of 453 proteins. While lysis with glass beads provided greater amounts of protein, CHAPS extraction buffer allowed identification of a higher number of proteins compared to SDS. Our data shows the impact of different protein isolation methods in the characterization of the S. epidermidis biofilm proteome. Furthermore, the correlation between proteomic and transcriptomic profiles was evaluated. The results confirmed that proteomic and transcriptomic data should be analyzed simultaneously in order to have a comprehensive understanding of a specific microbiological condition.
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Affiliation(s)
- Virginia Carvalhais
- CEB-Centre of Biological Engineering, LIBRO - Laboratory of Research in Biofilms Rosário Oliveira, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal; QOPNA, Mass Spectrometry Center, Department of Chemistry, University of Aveiro, Aveiro, Portugal; Division of Infectious diseases, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Angela França
- CEB-Centre of Biological Engineering, LIBRO - Laboratory of Research in Biofilms Rosário Oliveira, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal; Division of Infectious diseases, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Gerald B Pier
- Division of Infectious diseases, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Manuel Vilanova
- ICBAS-Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Porto, Portugal; IBMC-Instituto de Biologia Molecular e Celular, Rua do Campo Alegre 83, Porto, Portugal
| | - Nuno Cerca
- CEB-Centre of Biological Engineering, LIBRO - Laboratory of Research in Biofilms Rosário Oliveira, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
| | - Rui Vitorino
- QOPNA, Mass Spectrometry Center, Department of Chemistry, University of Aveiro, Aveiro, Portugal.
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Büttner FM, Zoll S, Nega M, Götz F, Stehle T. Structure-function analysis of Staphylococcus aureus amidase reveals the determinants of peptidoglycan recognition and cleavage. J Biol Chem 2014; 289:11083-11094. [PMID: 24599952 DOI: 10.1074/jbc.m114.557306] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The bifunctional major autolysin AtlA of Staphylococcus aureus cleaves the bacterium's peptidoglycan network (PGN) at two distinct sites during cell division. Deletion of the enzyme results in large cell clusters with disordered division patterns, indicating that AtlA could be a promising target for the development of new antibiotics. One of the two functions of AtlA is performed by the N-acetylmuramyl-l-alanine amidase AmiA, which cleaves the bond between the carbohydrate and the peptide moieties of PGN. To establish the structural requirements of PGN recognition and the enzymatic mechanism of cleavage, we solved the crystal structure of the catalytic domain of AmiA (AmiA-cat) in complex with a peptidoglycan-derived ligand at 1.55 Å resolution. The peptide stem is clearly visible in the structure, forming extensive contacts with protein residues by docking into an elongated groove. Less well defined electron density and the analysis of surface features indicate likely positions of the carbohydrate backbone and the pentaglycine bridge. Substrate specificity analysis supports the importance of the pentaglycine bridge for fitting into the binding cleft of AmiA-cat. PGN of S. aureus with l-lysine tethered with d-alanine via a pentaglycine bridge is completely hydrolyzed, whereas PGN of Bacillus subtilis with meso-diaminopimelic acid directly tethered with d-alanine is not hydrolyzed. An active site mutant, H370A, of AmiA-cat was completely inactive, providing further support for the proposed catalytic mechanism of AmiA. The structure reported here is not only the first of any bacterial amidase in which both the PGN component and the water molecule that carries out the nucleophilic attack on the carbonyl carbon of the scissile bond are present; it is also the first peptidoglycan amidase complex structure of an important human pathogen.
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Affiliation(s)
- Felix Michael Büttner
- Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Strasse 4, 72076 Tübingen, Germany
| | - Sebastian Zoll
- Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Strasse 4, 72076 Tübingen, Germany
| | - Mulugeta Nega
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany, and
| | - Friedrich Götz
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany, and
| | - Thilo Stehle
- Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Strasse 4, 72076 Tübingen, Germany,; Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
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The giant protein Ebh is a determinant of Staphylococcus aureus cell size and complement resistance. J Bacteriol 2013; 196:971-81. [PMID: 24363342 DOI: 10.1128/jb.01366-13] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Staphylococcus aureus USA300, the clonal type associated with epidemic community-acquired methicillin-resistant S. aureus (MRSA) infections, displays the giant protein Ebh on its surface. Mutations that disrupt the ebh reading frame increase the volume of staphylococcal cells and alter the cross wall, a membrane-enclosed peptidoglycan synthesis and assembly compartment. S. aureus ebh variants display increased sensitivity to oxacillin (methicillin) as well as susceptibility to complement-mediated killing. Mutations in ebh are associated with reduced survival of mutant staphylococci in blood and diminished virulence in mice. We propose that Ebh, following its secretion into the cross wall, contributes to the characteristic cell growth and envelope assembly pathways of S. aureus, thereby enabling complement resistance and the pathogenesis of staphylococcal infections.
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Missiakas DM, Schneewind O. Growth and laboratory maintenance of Staphylococcus aureus. CURRENT PROTOCOLS IN MICROBIOLOGY 2013; Chapter 9:Unit 9C.1. [PMID: 23408134 DOI: 10.1002/9780471729259.mc09c01s28] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Staphylococcus aureus is a facultative anaerobic Gram-positive coccus and a member of the normal skin flora as well as the nasal passages of humans. S. aureus is also the etiological agent of suppurative abscesses, as first described by Sir Alexander Ogston in 1880. Ever since, studies on S. aureus have focused on the complex battery of virulence factors and regulators that allow for its swift transition between commensalism and pathogenic states and escape from host immune defenses. The success of this pathogen is further evidenced by its ability to acquire antibiotic resistance traits through mechanisms that often remain poorly understood.
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Alegado RA, Brown LW, Cao S, Dermenjian RK, Zuzow R, Fairclough SR, Clardy J, King N. A bacterial sulfonolipid triggers multicellular development in the closest living relatives of animals. eLife 2012; 1:e00013. [PMID: 23066504 PMCID: PMC3463246 DOI: 10.7554/elife.00013] [Citation(s) in RCA: 179] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 07/18/2012] [Indexed: 12/15/2022] Open
Abstract
Bacterially-produced small molecules exert profound influences on animal health, morphogenesis, and evolution through poorly understood mechanisms. In one of the closest living relatives of animals, the choanoflagellate Salpingoeca rosetta, we find that rosette colony development is induced by the prey bacterium Algoriphagus machipongonensis and its close relatives in the Bacteroidetes phylum. Here we show that a rosette inducing factor (RIF-1) produced by A. machipongonensis belongs to the small class of sulfonolipids, obscure relatives of the better known sphingolipids that play important roles in signal transmission in plants, animals, and fungi. RIF-1 has extraordinary potency (femtomolar, or 10−15 M) and S. rosetta can respond to it over a broad dynamic range—nine orders of magnitude. This study provides a prototypical example of bacterial sulfonolipids triggering eukaryotic morphogenesis and suggests molecular mechanisms through which bacteria may have contributed to the evolution of animals. DOI:http://dx.doi.org/10.7554/eLife.00013.001 All animals, including humans, evolved in a world filled with bacteria. Although bacteria are most familiar as pathogens, some bacteria produce small molecules that are essential for the biology of animals and other eukaryotes, although the details of the ways in which these bacterial molecules are beneficial are not well understood. The choanoflagellates are water-dwelling organisms that use their whip-like flagella to move around, feeding on bacteria. They can exist as one cell or a colony of multiple cells and, perhaps surprisingly, are the closest known living relatives of animals. This means that experiments on these organisms have the potential to improve our understanding of animal development and the transition from egg to embryo to adult. Alegado et al. have explored how the morphology of Salpingoeca rosetta, a colony-forming choanoflagellate, is influenced by its interactions with various species of bacteria. In particular, they find that the development of multicellularity in S. rosetta is triggered by the presence of the bacterium Algoriphagus machipongonensis as well as its close relatives. They also identify the signaling molecule produced by the bacteria to be C32H64NO7S; this lipid molecule is an obscure relative of the sphingolipid molecules that have important roles in signal transmission in animals, plants, and fungi. Moreover, Alegado et al. show that S. rosetta can respond to this molecule – which they call rosette-inducing factor (RIF-1) – over a wide range of concentrations, including concentrations as low as 10−17 M. The work of Alegado et al. suggests that interactions between S. rosetta and Algoriphagus bacteria could be a productive model system for studying the influences of bacteria on animal cell biology, and for investigating the mechanisms of signal delivery and reception. Moreover, the molecular mechanisms revealed by this work leave open the possibility that bacteria might have contributed to the evolution of multicellularity in animals. DOI:http://dx.doi.org/10.7554/eLife.00013.002
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Affiliation(s)
- Rosanna A Alegado
- Department of Molecular and Cell Biology , University of California, Berkeley , Berkeley , United States
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20
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Tomoda H. [Mode of action of microbial anti-MRSA agents]. YAKUGAKU ZASSHI 2012; 132:37-44. [PMID: 22214578 DOI: 10.1248/yakushi.132.37] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) is known as a major nosocomial pathogen that has also developed resistance to many antibiotics. Moreover, MRSA resistance to a last-resort antibiotic, vancomycin, has been reported. Therefore, new anti-infectious agents to prevent and treat MRSA infection are needed. Based on this background, our group has focused on the discovery of new microbial agents active against MRSA infection. Viridicatumtoxin and spirohexaline, produced by Penicillium sp. FKI-3368, were isolated as inhibitors of undecaprenyl pyrophosphate (UPP) synthase of Staphylococcus aureus, which was involved in cell wall synthesis. Viridicatumtoxin and spirohexaline with a pentacyclic spiro skeleton inhibited UPP synthase activity with an IC(50) value of 4.0 and 9.0 µM, respectively. Actually, the growth of gram-positive bacteria including MRSA was strongly inhibited by the compounds. Our computational modeling experiments indicated that spirohexaline A was inserted into the substrate pocket of UPP synthase and interacted with Glu(88) via a carbamoyl group of the compound, with Ala(76), Met(54) and Asn(35) via three hydroxyl groups, and with certain hydrophobic amino acids via a spiro ring. Cyslabdan, produced by Streptomyces sp. K04-0144, was isolated as a potentiator of β-lactam imipenem activity against MRSA. The compound consisted of a labdan skeleton and an N-acetylcysteine. Cyslabdan potentiated imipenem activity by over 1000 fold, drastically reducing the MIC value of imipenem against MRSA from 16 to 0.03 µg/mL. The binding proteins of cyslabdan were investigated in the lysate of MRSA to identify FemA, which was involved in the formation of the pentaglycine interpeptide bridge in MRSA peptidoglycan.
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Affiliation(s)
- Hiroshi Tomoda
- Graduate School of Pharmaceutical Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
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Monteiro R, Vitorino R, Domingues P, Radhouani H, Carvalho C, Poeta P, Torres C, Igrejas G. Proteome of a methicillin-resistant Staphylococcus aureus clinical strain of sequence type ST398. J Proteomics 2012; 75:2892-915. [PMID: 22245554 DOI: 10.1016/j.jprot.2011.12.036] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Revised: 12/20/2011] [Accepted: 12/22/2011] [Indexed: 10/14/2022]
Abstract
Proteomics is a powerful tool to analyze the differences in gene expression of bacterial strains. Staphylococcus aureus has long been recognized as an important pathogen in human disease. In order to investigate this pathogen, the proteome of a clinical methicillin-resistant S. aureus (MRSA) strain of the sequence type ST398 was determined using 2-DE. Using 2-DE we obtained a total of 105 spots the MRSA strain. Furthermore in correlation with bioinformatic databases, they allowed accurate identification and characterization of proteins, resulting in 227 identified proteins. There were found proteins related to basic function of the cell, but also proteins related to virulence like catalase, specific of S. aureus species, and proteins related to antibiotic resistance. Proteins associated with antibiotic resistance or virulence factors are related to genomic databases. The most abundant classes identified involved glycolysis, energy production, one-carbon metabolism, and oxidation-reduction process, all of which reflect an active metabolism. These results highlight the importance of proteomics to deepen in the knowledge of protein expression of MRSA strain of the lineage ST398, microorganism with diverse and important resistance mechanisms. With this proteome map we have an essential tool for a better understanding of this pathogen and providing new data for protein databases. This article is part of a Special Issue entitled: Proteomics: The clinical link.
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Affiliation(s)
- R Monteiro
- Department of Genetics and Biotechnology, University of Trás-os-Montes and Alto Douro, Vila Real, Portugal
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In vivo synergism of ceftobiprole and vancomycin against experimental endocarditis due to vancomycin-intermediate Staphylococcus aureus. Antimicrob Agents Chemother 2011; 55:3977-84. [PMID: 21730114 DOI: 10.1128/aac.00402-11] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The efficacy of ceftobiprole combined with vancomycin was tested against two vancomycin-intermediate Staphylococcus aureus (VISA) strains, PC3 and Mu50, in rats with experimental endocarditis. Animals with infected aortic vegetations were treated for 3 days with doses simulating the kinetics after intravenous administration in humans of (i) the standard dose of ceftobiprole of 500 mg every 12 h (b.i.d.) (SD-ceftobiprole), (ii) a low dose of ceftobiprole of 250 mg b.i.d. (LD-ceftobiprole), (iii) a very low dose of ceftobiprole of 125 mg b.i.d. (VLD-ceftobiprole), (iv) SD-vancomycin of 1 g b.i.d., or (v) LD- or VLD-ceftobiprole combined with SD-vancomycin. Low dosages of ceftobiprole were purposely used to highlight positive drug interactions. Treatment with SD-ceftobiprole sterilized 12 of 14 (86%) and 10 of 13 (77%) vegetations infected with PC3 and Mu50, respectively (P < 0.001 versus controls). In comparison, LD-ceftobiprole sterilized 10 of 11 (91%) vegetations infected with PC3 (P < 0.01 versus controls) but only 3 of 12 (25%) vegetations infected with Mu50 (P > 0.05 versus controls). VLD-ceftobiprole and SD-vancomycin alone were ineffective against both strains (≤8% sterile vegetations). In contrast, the combination of VLD-ceftobiprole and SD-vancomycin sterilized 7 of 9 (78%) and 6 of 14 (43%) vegetations infected with PC3 and Mu50, respectively, and the combination of LD-ceftobiprole and SD-vancomycin sterilized 5 of 6 (83%) vegetations infected with Mu50 (P < 0.05 versus controls and monotherapy). Thus, ceftobiprole monotherapy simulating standard therapeutic doses was active against VISA experimental endocarditis. Moreover, subtherapeutic LD- and VLD-ceftobiprole synergized with ineffective vancomycin to restore efficacy. Hence, combining ceftobiprole with vancomycin broadens the therapeutic margin of these two compounds against VISA infections.
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Kern T, Giffard M, Hediger S, Amoroso A, Giustini C, Bui NK, Joris B, Bougault C, Vollmer W, Simorre JP. Dynamics Characterization of Fully Hydrated Bacterial Cell Walls by Solid-State NMR: Evidence for Cooperative Binding of Metal Ions. J Am Chem Soc 2010; 132:10911-9. [DOI: 10.1021/ja104533w] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Thomas Kern
- Institut de Biologie Structurale, UMR5075 (CEA/CNRS/UJF), 38027 Grenoble, France, Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF), FRE3200 (CEA/CNRS), INAC, CEA, 38054 Grenoble, France, Centre d’ingénierie des protéines, Institut de Chimie B6A, Université de Liège, Sart-Tilman, B4000 Liège, Belgium, and Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Richardson Road, Newcastle upon Tyne NE2 4AX, United Kingdom
| | - Mathilde Giffard
- Institut de Biologie Structurale, UMR5075 (CEA/CNRS/UJF), 38027 Grenoble, France, Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF), FRE3200 (CEA/CNRS), INAC, CEA, 38054 Grenoble, France, Centre d’ingénierie des protéines, Institut de Chimie B6A, Université de Liège, Sart-Tilman, B4000 Liège, Belgium, and Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Richardson Road, Newcastle upon Tyne NE2 4AX, United Kingdom
| | - Sabine Hediger
- Institut de Biologie Structurale, UMR5075 (CEA/CNRS/UJF), 38027 Grenoble, France, Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF), FRE3200 (CEA/CNRS), INAC, CEA, 38054 Grenoble, France, Centre d’ingénierie des protéines, Institut de Chimie B6A, Université de Liège, Sart-Tilman, B4000 Liège, Belgium, and Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Richardson Road, Newcastle upon Tyne NE2 4AX, United Kingdom
| | - Ana Amoroso
- Institut de Biologie Structurale, UMR5075 (CEA/CNRS/UJF), 38027 Grenoble, France, Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF), FRE3200 (CEA/CNRS), INAC, CEA, 38054 Grenoble, France, Centre d’ingénierie des protéines, Institut de Chimie B6A, Université de Liège, Sart-Tilman, B4000 Liège, Belgium, and Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Richardson Road, Newcastle upon Tyne NE2 4AX, United Kingdom
| | - Cécile Giustini
- Institut de Biologie Structurale, UMR5075 (CEA/CNRS/UJF), 38027 Grenoble, France, Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF), FRE3200 (CEA/CNRS), INAC, CEA, 38054 Grenoble, France, Centre d’ingénierie des protéines, Institut de Chimie B6A, Université de Liège, Sart-Tilman, B4000 Liège, Belgium, and Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Richardson Road, Newcastle upon Tyne NE2 4AX, United Kingdom
| | - Nhat Khai Bui
- Institut de Biologie Structurale, UMR5075 (CEA/CNRS/UJF), 38027 Grenoble, France, Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF), FRE3200 (CEA/CNRS), INAC, CEA, 38054 Grenoble, France, Centre d’ingénierie des protéines, Institut de Chimie B6A, Université de Liège, Sart-Tilman, B4000 Liège, Belgium, and Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Richardson Road, Newcastle upon Tyne NE2 4AX, United Kingdom
| | - Bernard Joris
- Institut de Biologie Structurale, UMR5075 (CEA/CNRS/UJF), 38027 Grenoble, France, Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF), FRE3200 (CEA/CNRS), INAC, CEA, 38054 Grenoble, France, Centre d’ingénierie des protéines, Institut de Chimie B6A, Université de Liège, Sart-Tilman, B4000 Liège, Belgium, and Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Richardson Road, Newcastle upon Tyne NE2 4AX, United Kingdom
| | - Catherine Bougault
- Institut de Biologie Structurale, UMR5075 (CEA/CNRS/UJF), 38027 Grenoble, France, Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF), FRE3200 (CEA/CNRS), INAC, CEA, 38054 Grenoble, France, Centre d’ingénierie des protéines, Institut de Chimie B6A, Université de Liège, Sart-Tilman, B4000 Liège, Belgium, and Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Richardson Road, Newcastle upon Tyne NE2 4AX, United Kingdom
| | - Waldemar Vollmer
- Institut de Biologie Structurale, UMR5075 (CEA/CNRS/UJF), 38027 Grenoble, France, Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF), FRE3200 (CEA/CNRS), INAC, CEA, 38054 Grenoble, France, Centre d’ingénierie des protéines, Institut de Chimie B6A, Université de Liège, Sart-Tilman, B4000 Liège, Belgium, and Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Richardson Road, Newcastle upon Tyne NE2 4AX, United Kingdom
| | - Jean-Pierre Simorre
- Institut de Biologie Structurale, UMR5075 (CEA/CNRS/UJF), 38027 Grenoble, France, Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF), FRE3200 (CEA/CNRS), INAC, CEA, 38054 Grenoble, France, Centre d’ingénierie des protéines, Institut de Chimie B6A, Université de Liège, Sart-Tilman, B4000 Liège, Belgium, and Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Richardson Road, Newcastle upon Tyne NE2 4AX, United Kingdom
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Volz T, Nega M, Buschmann J, Kaesler S, Guenova E, Peschel A, Röcken M, Götz F, Biedermann T. Natural Staphylococcus aureus-derived peptidoglycan fragments activate NOD2 and act as potent costimulators of the innate immune system exclusively in the presence of TLR signals. FASEB J 2010; 24:4089-102. [PMID: 20522786 DOI: 10.1096/fj.09-151001] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Innate immune sensing of Staphylococcus aureus unravels basic mechanisms leading to either effective antibacterial immune responses or harmful inflammation. The nature and properties of S. aureus-derived pathogen-associated molecular pattern (PAMPs) are still not completely understood. We investigated the innate immune sensing of peptidoglycan (PGN) structures and subsequent immune consequences. Macromolecular PGN (PGN(polymer)) preparations activated NF-κB through human Toll-like receptors 2 (TLR2), as shown by luciferase reporter assays, and induced murine dendritic cell (DC) maturation and cytokine production. In contrast, PGN(polymer) from lgt-mutant S. aureus failed to stimulate human TLR2, demonstrating that lipoproteins within the macromolecular structures of PGN(polymer), but not PGN itself, activate TLR2. Thus, HPLC-purified monomeric PGN (PGN(monomer)) structures were investigated. Strikingly, PGN(monomer) completely lacked NF-κB activation, lacked TLR2 activity, and failed to functionally activate murine DCs. However, PGN(monomer) in concert with various TLR ligands most effectively stimulated DCs to up-regulate IL-12p70 and IL-23 by ≥3- to 5-fold. Consequently, DCs coactivated by PGN(monomer) markedly up-regulated Th1 and Th17 while suppressing Th2 cell priming. Notably, PGN(monomer) failed to coactivate NOD2(-/-) DCs. This demonstrates that PGN(monomer) is a natural ligand of NOD2, which was previously only demonstrated for synthetic compounds like muramyl dipeptide. Interestingly, murine DCs lacking TLR2 remained mute in response to the combinative immune sensing of S. aureus-derived PAMPs, including PGN(monomer), providing for the first time an explanation of why S. aureus can colonize the nasal mucosa in the absence of inflammation. This is very likely based on the lack of TLR2 expression in mucosal epithelial cells under normal conditions, which determines the unresponsiveness to S. aureus PAMPs.
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Affiliation(s)
- Thomas Volz
- Department of Dermatology, Eberhard Karls University, Liebermeisterstrasse 25, 72076 Tübingen, Germany
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25
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Comparative study of the susceptibilities of major epidemic clones of methicillin-resistant Staphylococcus aureus to oxacillin and to the new broad-spectrum cephalosporin ceftobiprole. Antimicrob Agents Chemother 2008; 52:2709-17. [PMID: 18505853 DOI: 10.1128/aac.00266-08] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Multidrug-resistant strains of Staphylococcus aureus continue to increase in frequency worldwide, both in hospitals and in the community, raising serious problems for the chemotherapy of staphylococcal disease. Ceftobiprole (BPR; BAL9141), the active constituent of the prodrug ceftobiprole medocaril (BAL5788), is a new cephalosporin which was already shown to have powerful activity against a number of bacterial pathogens, including S. aureus. In an effort to test possible limits to the antibacterial spectrum and efficacy of BPR, we examined the susceptibilities of the relatively few pandemic methicillin-resistant S. aureus (MRSA) clones that are responsible for the great majority of cases of staphylococcal disease worldwide. We also included in the tests the highly oxacillin-resistant subpopulations that are present with low frequencies in the cultures of these clones. Such subpopulations may represent a natural reservoir from which MRSA strains with decreased susceptibility to BPR may emerge in the future. We also tested the efficacy of BPR against MRSA strains with reduced susceptibility to vancomycin and against MRSA strains carrying the enterococcal vancomycin resistance gene complex. BPR was shown to be uniformly effective against all these resistant MRSA strains, and the mechanism of superb antimicrobial activity correlated with the strikingly increased affinity of the cephalosporin against penicillin-binding protein 2A, the protein product of the antibiotic resistance determinant mecA.
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Ellington JK, Harris M, Hudson MC, Vishin S, Webb LX, Sherertz R. Intracellular Staphylococcus aureus and antibiotic resistance: implications for treatment of staphylococcal osteomyelitis. J Orthop Res 2006; 24:87-93. [PMID: 16419973 DOI: 10.1002/jor.20003] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
UNLABELLED Staphylococcus aureus is responsible for 80% of human osteomyelitis. It can invade and persist within osteoblasts. Antibiotic resistant strains of S. aureus make successful treatment of osteomyelitis difficult. NULL HYPOTHESIS antibiotic sensitivities of S. aureus do not change after exposure to the osteoblast intracellular environment. Human and mouse osteoblast cultures were infected and S. aureus cells were allowed to invade. Following times 0, 12, 24, and 48 h ( +/- the addition of erythromycin, clindamycin, and rifampin at times 0 or 12 h), the osteoblasts were lysed and intracellular bacteria enumerated. Transmission electron microscopy was performed on extracellular and intracellular S. aureus cells. In mouse osteoblasts, administration of bacteriostatic antibiotics at time 0 prevented the increase in intracellular S. aureus. If the antibiotics were delayed 12 h, this did not occur. When rifampin (bactericidal) was introduced at time 0 to human and mouse osteoblasts, there was a significant decrease in number of intracellular S. aureus within osteoblasts compared to control. If rifampin was delayed 12 h, this did not occur. Significant time-dependent S. aureus structural changes were observed after exposure to the osteoblast intracellular environment. These studies demonstrate that once S. aureus is established intracellularly for 12 h, the bacteria are less sensitive to antibiotics capable of eukaryotic cell penetration (statistically significant). These antibiotic sensitivity changes could be due in part to the observed structural changes. This leads to the rejection of our null hypotheses that the antibiotic sensitivities of S. aureus are unaltered by their location.
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Affiliation(s)
- J Kent Ellington
- Department of Orthopaedic Surgery, Carolinas Medical Center, 1000 Blythe Boulevard, Charlotte, North Carolina 28223, USA
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Severin A, Wu SW, Tabei K, Tomasz A. High-level (beta)-lactam resistance and cell wall synthesis catalyzed by the mecA homologue of Staphylococcus sciuri introduced into Staphylococcus aureus. J Bacteriol 2005; 187:6651-8. [PMID: 16166526 PMCID: PMC1251583 DOI: 10.1128/jb.187.19.6651-6658.2005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A close homologue of mecA, the determinant of broad-spectrum beta-lactam resistance in Staphylococcus aureus was recently identified as a native gene in the animal commensal species Staphylococcus sciuri. Introduction of the mecA homologue from a methicillin-resistant strain of S. sciuri into a susceptible strain of S. aureus caused an increase in drug resistance and allowed continued growth and cell wall synthesis of the bacteria in the presence of high concentrations of antibiotic. We determined the muropeptide composition of the S. sciuri cell wall by using a combination of high-performance liquid chromatography, mass spectrometric analysis, and Edman degradation. Several major differences between the cell walls of S. aureus and S. sciuri were noted. The pentapeptide branches in S. sciuri were composed of one alanine and four glycine residues in contrast to the pentaglycine units in S. aureus. The S. sciuri wall but not the wall of S. aureus contained tri- and tetrapeptide units, suggesting the presence of dd- and ld-carboxypeptidase activity. Most interestingly, S. aureus carrying the S. sciuri mecA and growing in methicillin-containing medium produced a cell wall typical of S. aureus and not S. sciuri, in spite of the fact that wall synthesis under these conditions had an absolute dependence on the heterologous S. sciuri gene product. The protein product of the S. sciuri mecA can efficiently participate in cell wall biosynthesis and build a cell wall using the cell wall precursors characteristic of the S. aureus host.
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Affiliation(s)
- Anatoly Severin
- Rockefeller University, 1230 York Ave., New York, NY 10021, USA
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Bera A, Herbert S, Jakob A, Vollmer W, Götz F. Why are pathogenic staphylococci so lysozyme resistant? The peptidoglycan O-acetyltransferase OatA is the major determinant for lysozyme resistance of Staphylococcus aureus. Mol Microbiol 2005; 55:778-87. [PMID: 15661003 DOI: 10.1111/j.1365-2958.2004.04446.x] [Citation(s) in RCA: 335] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Staphylococcus species belong to one of the few bacterial genera that are completely lysozyme resistant, which greatly contributes to their persistence and success in colonizing the skin and mucosal areas of humans and animals. In an attempt to discover the cause of lysozyme resistance, we identified a gene, oatA, in Staphylococcus aureus. The corresponding oatA deletion mutant had an increased sensitivity to lysozyme. HPLC and electrospray ionization tandem mass spectrometry analyses of the cell wall revealed that the muramic acid of peptidoglycan of the wild-type strain was O-acetylated at C6-OH, whereas the muramic acid of the oatA mutant lacked this modification. The complemented oatA mutant was lysozyme resistant. We identified the first bacterial peptidoglycan-specific O-acetyltransferase in S. aureus and showed that OatA, an integral membrane protein, is the molecular basis for the high lysozyme resistance in staphylococci.
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Affiliation(s)
- Agnieszka Bera
- Microbial Genetics, University of Tübingen, D-72076 Tübingen, Auf der Morgenstelle, Germany
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29
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Sato Y, Shibata H, Arai T, Yamamoto A, Okimura Y, Arakaki N, Higuti T. Variation in synergistic activity by flavone and its related compounds on the increased susceptibility of various strains of methicillin-resistant Staphylococcus aureus to beta-lactam antibiotics. Int J Antimicrob Agents 2005; 24:226-33. [PMID: 15325425 DOI: 10.1016/j.ijantimicag.2004.02.028] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2003] [Accepted: 02/04/2004] [Indexed: 10/26/2022]
Abstract
We found that some flavonoids had a weak antibacterial effect on methicillin-resistant Staphylococcus aureus (MRSA), but that at sub-MIC concentrations they greatly increased the susceptibility of these strains to beta-lactam antibiotics. Flavone showed diverse synergistic effects on the susceptibility of MRSA to beta-lactam antibiotics. The variation of the synergistic effects of the flavones to increase the susceptibility of strains of MRSA to beta-lactam antibiotics coincided with their varying effects on growth-inhibition of these strains. Based on these findings, we have proposed a model for the mechanisms of high resistance of MRSA to beta-lactams and the massive reduction in the beta-lactams MIC caused by flavones.
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Affiliation(s)
- Youichi Sato
- Department of Molecular Cell Biology and Medicine, Institute of Health Biosciences, The University of Tokushima, 1-78, Shomachi, Tokushima 770-8505, Japan
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30
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Pinho MG, Errington J. Dispersed mode of Staphylococcus aureus cell wall synthesis in the absence of the division machinery. Mol Microbiol 2004; 50:871-81. [PMID: 14617148 DOI: 10.1046/j.1365-2958.2003.03719.x] [Citation(s) in RCA: 184] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have developed several new fluorescent staining procedures that enabled us to study the synthesis of cell wall material in the spherical Gram-positive bacterium Staphylococcus aureus. The results obtained support previous proposals that these cells synthesize new wall material specifically at cell division sites, in the form of a flat circular plate that is subsequently cleaved and remodelled to produce the new hemispherical poles of the daughter cells. We have shown that formation of the septal peptidoglycan is dependent on the key cell division protein FtsZ, which recruits penicillin-binding protein (PBP) 2. Unexpectedly, in FtsZ-depleted cells, the cell wall synthetic machinery becomes dispersed and new wall material is made in dispersed patches over the entire surface of the cells, which increase in volume by up to eightfold before lysing. The results have implications for understanding the nature of S. aureus morphogenesis and for inhibitors of cell division proteins as drug targets.
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Affiliation(s)
- Mariana G Pinho
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
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31
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De Jonge BLM, Gage D, Xu N. The carboxyl terminus of peptidoglycan stem peptides is a determinant for methicillin resistance in Staphylococcus aureus. Antimicrob Agents Chemother 2002; 46:3151-5. [PMID: 12234837 PMCID: PMC128806 DOI: 10.1128/aac.46.10.3151-3155.2002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A mecA-containing Staphylococcus aureus strain was grown in the presence of high concentrations of D-serine, D-threonine, and D-phenylalanine. These growth conditions resulted in the replacement of the carboxyl-terminal (fifth) D-alanine residue of peptidoglycan stem peptides with the D-amino acid present in the growth medium and a reduced ability to grow in the presence of methicillin. The most dramatic effect was seen with D-serine. With 32 mM D-serine, strains that had been able to grow in the presence of 800 micro g of methicillin per ml were only able to grow in the presence of less than 50 micro g/ml. The results also suggest that in S. aureus vancomycin resistance mediated through the incorporation of precursors not terminating in D-alanyl-D-alanine would be mutually exclusive with expression of mecA-mediated methicillin resistance.
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Cordwell SJ, Larsen MR, Cole RT, Walsh BJ. Comparative proteomics of Staphylococcus aureus and the response of methicillin-resistant and methicillin-sensitive strains to Triton X-100. MICROBIOLOGY (READING, ENGLAND) 2002; 148:2765-2781. [PMID: 12213923 DOI: 10.1099/00221287-148-9-2765] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Proteomics is a powerful tool for analysing differences in gene expression between bacterial strains with alternate phenotypes. Staphylococcus aureus strains are grouped on the basis of their sensitivity to methicillin. Two-dimensional gel electrophoresis was combined with MS to compare the protein profiles of S. aureus strains COL (methicillin-resistant) and 8325 (methicillin-sensitive). Reference mapping via this approach identified 377 proteins that corresponded to 266 distinct ORFs. Amongst these identified proteins were 14 potential virulence factors. The production of 41 'hypothetical' proteins was confirmed, and eight of these appeared to be unique to S. aureus. Strain COL displayed 12 protein spots, which included alkaline-shock protein 23 (Asp23) and cold-shock proteins CspABC, which either were not present in strain 8325 or were present at a significantly lower intensity in this strain. Comparative maps were used to characterize the S. aureus response to treatment with Triton X-100 (TX-100), a detergent that has been shown to reduce methicillin resistance independently of an interaction with the mecA-encoded penicillin-binding protein 2a. In response to growth of the bacteria in the presence of TX-100, 44 protein spots showed altered levels of abundance, and 11 of these spots were found only in COL. The products of genes regulated by sigma(B) (the alternative sigma factor), including Asp23 and three proteins of unknown function, and SarA (a regulator of virulence genes) were shown to be present at significantly altered levels. SarA production was induced in TX-100-treated cultures. A protein of the sigma(B) operon, RsbV, was only detected in COL and its production was down-regulated in COL when the strain was treated with TX-100, whereas RsbW was present at reduced levels in both strains. Upon growth of both strains in the presence of TX-100, no effects on the production of the essential methicillin-resistance factor FemA were detected, whereas phosphoglucosamine mutase (GlmM) production was reduced in COL alone. This study suggests that proteins of the sigma(B) and sarA regulons, as well as other factors, are involved in methicillin resistance in S. aureus.
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Affiliation(s)
- Stuart J Cordwell
- Australian Proteome Analysis Facility, Level 4, Building F7B, Macquarie University, Sydney, Australia21091
| | - Martin R Larsen
- Australian Proteome Analysis Facility, Level 4, Building F7B, Macquarie University, Sydney, Australia21091
| | - Rebecca T Cole
- Australian Proteome Analysis Facility, Level 4, Building F7B, Macquarie University, Sydney, Australia21091
| | - Bradley J Walsh
- Australian Proteome Analysis Facility, Level 4, Building F7B, Macquarie University, Sydney, Australia21091
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33
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Wu S, de Lencastre H, Sali A, Tomasz A. A phosphoglucomutase-like gene essential for the optimal expression of methicillin resistance in Staphylococcus aureus: molecular cloning and DNA sequencing. Microb Drug Resist 2000; 2:277-86. [PMID: 9158773 DOI: 10.1089/mdr.1996.2.277] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
We describe here the cloning and sequencing of a new auxiliary gene identified by Tn551 insertional mutagenesis of the highly and homogeneously methicillin-resistant Staphylococcus aureus strain COL. The insertionally inactivated mutant RUSA315 had intact mecA and normal amounts of PBP2A, but drastically reduced antibiotic resistance (drop in methicillin MIC from 1600 to 1.5 micrograms ml-1), a unique heterogeneous phenotype, and a compositional change in the cell wall characterized by the complete disappearance of the unsubstituted disaccharide pentapeptide from the peptidoglycan. Cloning in E. coli followed by sequencing located the Tn551 insert omega 720 in an open reading frame of 451 codons, provisionally called femR315, defining a polypeptide with a deduced amino acid sequence that showed over 26% sequence identity and 57% overall sequence similarity with the phosphoglucomutase (PGM) gene of E. coli. The Tn551 insertion site of a previously described mutant 12F (femD) also lies in the same gene as femR315. The wild-type form of femR315 subcloned in a shuttle vector fully restored expression of high level (parental) methicillin resistance in mutant RUSA315. The exact biochemical function of femR315 is not known. However, enzymes similar to PGM catalyze the isomerization of hexose and hexosamine phosphates leading to the formation of glucosamine-1-P, which is an obligate precursor in the biosynthesis of UDP-N-acetylglucosamine (UDP-NAGA). We propose that the suppression of methicillin resistance in RUSA315 is related to some functional or quantitative abnormality of UDP-NAGA metabolism.
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Affiliation(s)
- S Wu
- Laboratory of Microbiology, Rockefeller University, New York, New York 10021-6399, USA
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34
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Ludovice AM, Wu SW, de Lencastre H. Molecular cloning and DNA sequencing of the Staphylococcus aureus UDP-N-acetylmuramyl tripeptide synthetase (murE) gene, essential for the optimal expression of methicillin resistance. Microb Drug Resist 2000; 4:85-90. [PMID: 9650993 DOI: 10.1089/mdr.1998.4.85] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The Tn551 insertion in mutant RUSA235 of a highly methicillin resistant Staphylococcus aureus strain results in drastic reduction in the level of methicillin resistance and abnormalities, both in the composition of the peptidoglycan and of the cell wall precursor pool. Cloning and sequencing of the inactivated gene indicates that it is the murE gene of Staphylococcus aureus.
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Affiliation(s)
- A M Ludovice
- Molecular Genetics Unit, Instituto de Technologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
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35
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Kopp U, Roos M, Wecke J, Labischinski H. Staphylococcal peptidoglycan interpeptide bridge biosynthesis: a novel antistaphylococcal target? Microb Drug Resist 2000; 2:29-41. [PMID: 9158720 DOI: 10.1089/mdr.1996.2.29] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In staphylococci, crosslinking of the peptide moiety of peptidoglycan is mediated via an additional spacer, the interpeptide bridge, consisting of five glycine residues. The femAB operon, coding for two approximately 50-kDa proteins is known to be involved in pentaglycine bridge formation. Using chemical mutagenesis of the beta-lactam-resistant strain BB270 and genetic, biochemical, and biophysical characterization of mutants selected for loss of beta-lactam resistance and reduced lysostaphin sensitivity it is shown that peptide bridge formation proceeds via three intermediate bridge lengths (cell wall peptides with no, one, three, and five glycine units). To proceed from one intermediate to the next, three genes appear necessary: femX, femA, and femB. The drastic loss of beta-lactam resistance after inactivation of FemA or partial impairment of FemX even beyond the level of the sensitive wild-type strains renders these proteins attractive antistaphylococcal targets.
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Affiliation(s)
- U Kopp
- Bayer AG, Pharma Research Antiinfectives I, Wuppertal, Germany
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36
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De Lencastre H, Wu SW, Pinho MG, Ludovice AM, Filipe S, Gardete S, Sobral R, Gill S, Chung M, Tomasz A. Antibiotic resistance as a stress response: complete sequencing of a large number of chromosomal loci in Staphylococcus aureus strain COL that impact on the expression of resistance to methicillin. Microb Drug Resist 2000; 5:163-75. [PMID: 10566865 DOI: 10.1089/mdr.1999.5.163] [Citation(s) in RCA: 131] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Tn551 inactivation has identified several determinants--fem or auxiliary genes--that, in addition to the mecA gene, are also critical for the expression of high-level and homogeneous resistance to methicillin. Genetic and/or biochemical analysis has shown that of the nearly dozen aux mutations described so far most are in genes involved in cell wall synthesis (murE, pbp2, glmM, glnR, femA/B, llm, etc.) or in complex regulatory functions (sigmaB), suggesting that optimal expression of resistance may involve the cooperative functioning of a number of genes in cell wall metabolism as well as stress response. The exact mechanism of these functions is not known. In an attempt to explore this unusual aspect of methicillin resistance more fully, a Tn551 transposon library, constructed in the background of the highly and homogeneously methicillin-resistant Staphylococcus aureus strain COL, was screened for all independent insertional mutants in which the level of methicillin resistance of the parental strain (MIC, 1,600 microg/ml) was reduced by at least 15-fold and up to 500-fold. We now describe the sequencing of 21 Tn551-inactivated genes and their vicinities in 23 new auxiliary mutants that have been studied before. Using the inverted polymerase chain reaction (IPCR), we amplified fragments corresponding to the right and left junction of the Tn551 insertions, which were then sequenced by primer walking. The two largest groups of these new auxiliary genes encoded either proteins of unknown functions (6 genes) or showed homology with genes encoding proteins involved with putative sensory/regulatory activities (7 genes: protein kinases, ABC transporters, and a catabolite control protein). Sequencing upstream and downstream allowed the identification of a number of additional open reading frames, some of which may also include functions relevant for the expression of antibiotic resistance.
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Affiliation(s)
- H De Lencastre
- Laboratory of Microbiology, The Rockefeller University, New York, NY 10021, USA
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37
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Wu SW, De Lencastre H. Mrp--a new auxiliary gene essential for optimal expression of methicillin resistance in Staphylococcus aureus. Microb Drug Resist 2000; 5:9-18. [PMID: 10332717 DOI: 10.1089/mdr.1999.5.9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Screening of a library of Tn551 insertional mutants selected for reduction in the methicillin resistance level of the parental Staphylococcus aureus strain COL resulted in the isolation of mutant RUSA266 in which the minimal inhibitory concentration (MIC) of the parent was reduced from 1,600 to 1.5 micrograms/mL. Cloning and sequencing of the vicinity of the insertion site omega 726 identified an open reading frame (orf1365) encoding a very large polypeptide of more than 1,365 amino acids. A unique feature of the deduced amino acid sequence was the presence of multiple tandem repeats of 75 amino acids in the polypeptide, reminiscent of the structure of high-molecular-weight cell-surface proteins EF* and Emb identified in some streptococcal strains. Mutant RUSA266 with the inactivated gene, which we shall provisionally refer to as mrp (for multiple repeat polypeptide), produced a peptidoglycan with altered muropeptide composition, and both the reduced antibiotic resistance and the altered cell wall composition were co-transduced in back-crosses into the parental strain COL. Additional sequencing upstream of mrp has revealed that this gene was part of a five-gene cluster occupying a 9.2-kb region of the staphylococcal chromosome and was composed of glmM (directly upstream of mrp), two open reading frames orf310 and orf269 coding for two hypothetical proteins, and the gene encoding the staphylococcal arginase (arg). Transcriptional analysis demonstrated that the five genes in the cluster were transcribed together.
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Affiliation(s)
- S W Wu
- Laboratory of Microbiology, Rockefeller University, New York, NY, USA
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38
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Glanzmann P, Gustafson J, Komatsuzawa H, Ohta K, Berger-Bächi B. glmM operon and methicillin-resistant glmM suppressor mutants in Staphylococcus aureus. Antimicrob Agents Chemother 1999; 43:240-5. [PMID: 9925512 PMCID: PMC89057 DOI: 10.1128/aac.43.2.240] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Staphylococcus aureus phosphoglucosamine mutase gene glmM was shown to be the last gene of a three-cistron operon, orf1-orf2-glmM. One transcriptional start was identified upstream of orf1, and a second start producing a monocistronic transcript was identified upstream of glmM. Disruption of glmM abolished GlmM production, decreased methicillin resistance, and resulted in teicoplanin hypersusceptibility without affecting the production of the endogenous penicillin-binding proteins and PBP 2'. Complementation of the glmM mutation by the complete glmM operon restored both methicillin resistance and normal teicoplanin susceptibility. In contrast, a highly methicillin-resistant suppressor mutant obtained by selection for growth in the presence of methicillin remained GlmM deficient and teicoplanin hypersusceptible. The suppressor mutation was not linked to the glmM operon but was correlated with decreased autolysis and increased production of a 49-kDa protein, suggesting that there is an alternative pathway for glucosamine-1-phosphate synthesis in S. aureus.
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Affiliation(s)
- P Glanzmann
- Institute for Medical Microbiology, University of Zürich, Switzerland
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39
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Giesbrecht P, Kersten T, Maidhof H, Wecke J. Staphylococcal cell wall: morphogenesis and fatal variations in the presence of penicillin. Microbiol Mol Biol Rev 1998; 62:1371-414. [PMID: 9841676 PMCID: PMC98950 DOI: 10.1128/mmbr.62.4.1371-1414.1998] [Citation(s) in RCA: 194] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The primary goal of this review is to provide a compilation of the complex architectural features of staphylococcal cell walls and of some of their unusual morphogenetic traits including the utilization of murosomes and two different mechanisms of cell separation. Knowledge of these electron microscopic findings may serve as a prerequisite for a better understanding of the sophisticated events which lead to penicillin-induced death. For more than 50 years there have been controversial disputes about the mechanisms by which penicillin kills bacteria. Many hypotheses have tried to explain this fatal event biochemically and mainly via bacteriolysis. However, indications that penicillin-induced death of staphylococci results from overall biochemical defects or from a fatal attack of bacterial cell walls by bacteriolytic murein hydrolases were not been found. Rather, penicillin, claimed to trigger the activity of murein hydrolases, impaired autolytic wall enzymes of staphylococci. Electron microscopic investigations have meanwhile shown that penicillin-mediated induction of seemingly minute cross wall mistakes is the very reason for this killing. Such "morphogenetic death" taking place at predictable cross wall sites and at a predictable time is based on the initiation of normal cell separations in those staphylococci in which the completion of cross walls had been prevented by local penicillin-mediated impairment of the distribution of newly synthesized peptidoglycan; this death occurs because the high internal pressure of the protoplast abruptly kills such cells via ejection of some cytoplasm during attempted cell separation. An analogous fatal onset of cell partition is considered to take place without involvement of a detectable quantity of autolytic wall enzymes ("mechanical cell separation"). The most prominent feature of penicillin, the disintegration of bacterial cells via bacteriolysis, is shown to represent only a postmortem process resulting from shrinkage of dead cells and perturbation of the cytoplasmic membrane. Several schematic drawings have been included in this review to facilitate an understanding of the complex morphogenetic events.
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40
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Navarre WW, Ton-That H, Faull KF, Schneewind O. Anchor structure of staphylococcal surface proteins. II. Cooh-terminal structure of muramidase and amidase-solubilized surface protein. J Biol Chem 1998; 273:29135-42. [PMID: 9786922 DOI: 10.1074/jbc.273.44.29135] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Surface proteins of the Gram-positive organism Staphylococcus aureus are anchored to the bacterial cell wall by a transpeptidation mechanism during which the polypeptide is cleaved between the threonine (T) and the glycine (G) of the LPXTG motif. The carboxyl of threonine is subsequently amide linked to the amino of the pentaglycyl cross-bridge within the staphylococcal peptidoglycan. Previous work examined the anchor structure of surface proteins solubilized from the peptidoglycan by treatment with lysostaphin or phi11 hydrolase and identified COOH-terminally linked triglycyl or L-Ala-D-iGln-L-Lys(Gly5)-D-Ala and MurNAc-[L-Ala-D-iGln-L-Lys(Gly5)-D-Ala](beta1-4)-GlcNAc, respectively. Here, we report the anchor structure of surface proteins solubilized with N-acetylmuramidase and N-acetylmuramyl-L-alanine amidase. N-Acetylmuramidase-released surface protein was linked to MurNAc-[L-Ala-D-iGln-L-Lys(Gly5)-D-Ala](beta1-4)-GlcNAc, whereas N-acetylmuramyl-L-alanine amidase treatment of the cell wall solubilized surface proteins linked to L-Ala-D-iGln-L-Lys(Gly5)-D-Ala. Most, but not all, anchor structures were cross-linked to other cell wall subunits, in which the D-alanyl at position four was amide linked to the pentaglycyl of a neighboring wall peptide.
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Affiliation(s)
- W W Navarre
- Department of Microbiology and Immunology, UCLA School of Medicine, Los Angeles, California 90095, USA
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41
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Ohta K, Komatsuzawa H, Sugai M, Suginaka H. Zymographic characterization of Staphylococcus aureus cell wall. Microbiol Immunol 1998; 42:231-5. [PMID: 9570289 DOI: 10.1111/j.1348-0421.1998.tb02276.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Susceptibilities of several preparations of Staphylococcus aureus cells to various peptidoglycan hydrolases with known bond specificity were analyzed by zymography. The substrates were intact S. aureus cells, cells boiled in the presence of SDS and cells treated with trichloroacetic acid after treatment with boiling SDS solution (TCA-cells). Twofold dilutions of lysostaphin (LS), lysozyme (LZ), S. aureus 51 kDa glucosaminidase (GL) or S. aureus 62 kDa amidase (AM) were electrophoresed, and the minimal enzyme dose showing a visible bacteriolytic band was defined as MBD (minimal bacteriolytic dose). Under the same experimental conditions, this method gave reproducible results. As the substrate for zymogram, TCA-cells were the most sensitive to LS, LZ and AM, whereas the three substrate were equally sensitive to GL. A zymographic analysis of methicillin-resistant S. aureus treated with methicillin together with previous studies suggest that this method can be used for the preliminary characterization of S. aureus cell wall peptidoglycan.
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Affiliation(s)
- K Ohta
- Department of Microbiology, Hiroshima University School of Dentistry, Hiroshima, Japan
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42
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Toney JH, Hammond GG, Leiting B, Pryor KD, Wu JK, Cuca GC, Pompliano DL. Soluble penicillin-binding protein 2a: beta-lactam binding and inhibition by non-beta-lactams using a 96-well format. Anal Biochem 1998; 255:113-9. [PMID: 9448849 DOI: 10.1006/abio.1997.2458] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
High level methicillin resistance in Staphylococcus aureus is dependent upon the acquisition of the mecA gene encoding penicillin-binding protein 2a (PBP2a). PBP2a is a member of a family of peptidoglycan biosynthetic enzymes involved in assembly of the cell wall in bacteria and is poorly inactivated by beta-lactam antibiotics. We describe a 96-well-filter binding assay using recombinant, soluble PBP2a which allows for kinetic measurement of penicillin binding. The deacylation rate constant for the PBP2a-penicillin G covalent complex was found to be 5.7 +/- 1.0 x 10(-5) s-1 at 30 degrees C (half-life of approximately 200 min). For the PBP2a acylation reaction, the value of K(m) (penicillin G) = 0.5 +/- 0.1 mM and kcat = 1 x 10(-3) s-1, which yields a second-order rate constant (kcat/K(m)) for inactivation of 2.0 M-1 s-1. Using this assay, several non-beta-lactam inhibitors including Cibacron blue have been found which exhibit IC50 values between 10 and 30 microM. The binding affinities of several carbapenems and beta-lactams correlated well between the filter binding assay described in this report and an electrophoretic assay for PBP2a using membranes prepared form methicillin-resistant S. aureus.
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Affiliation(s)
- J H Toney
- Department of Biochemistry, Merck Research Laboratories, Rahway, New Jersey 07065-0900, USA.
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43
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Maranan MC, Moreira B, Boyle-Vavra S, Daum RS. Antimicrobial resistance in staphylococci. Epidemiology, molecular mechanisms, and clinical relevance. Infect Dis Clin North Am 1997; 11:813-49. [PMID: 9421702 DOI: 10.1016/s0891-5520(05)70392-5] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Staphylococcal infections continue to pose important clinical problems in children and adults. Antibiotic resistance among the staphylococci has rendered therapy of these infections a therapeutic challenge. Despite early, uniform susceptibility to penicillin, staphylococci acquired a gene elaborating beta-lactamase that rendered penicillin inactive and that is borne by nearly all clinical isolates. "Penicillinase-resistant beta-lactams," such as methicillin, were introduced in the early 1960s, but resistance to them has become an increasing concern. The mechanism of the so-called "methicillin resistance" is complex. Moreover, once confined to the ecology of hospitals and other institutions, a recent increase in community-acquired methicillin-resistant S. aureus infections has been observed. Glycopeptides, until now the only uniformly reliable therapeutic modality, have been increasingly used for therapy of staphylococcal infections. The recent recognition of clinical isolates with reduced susceptibility to glycopeptides is of concern.
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Affiliation(s)
- M C Maranan
- Department of Pediatrics, University of Chicago, Illinois, USA
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44
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Chambers HF. Methicillin resistance in staphylococci: molecular and biochemical basis and clinical implications. Clin Microbiol Rev 1997; 10:781-91. [PMID: 9336672 PMCID: PMC172944 DOI: 10.1128/cmr.10.4.781] [Citation(s) in RCA: 605] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Methicillin resistance in staphylococci is determined by mec, composed of 50 kb or more of DNA found only in methicillin-resistant strains. mec contains mecA, the gene for penicillin-binding protein 2a (PBP 2a); mecI and mecR1, regulatory genes controlling mecA expression; and numerous other elements and resistance determinants. A distinctive feature of methicillin resistance is its heterogeneous expression. Borderline resistance, a low-level type of resistance to methicillin exhibited by strains lacking mecA, is associated with modifications in native PBPs, beta-lactamase hyperproduction, or possibly a methicillinase. The resistance phenotype is influenced by numerous factors, including mec and beta-lactamase (bla) regulatory elements, fem factors, and yet to be identified chromosomal loci. The heterogeneous nature of methicillin resistance confounds susceptibility testing. Methodologies based on the detection of mecA are the most accurate. Vancomycin is the drug of choice for treatment of infection caused by methicillin-resistant strains. PBP 2a confers cross-resistance to most currently available beta-lactam antibiotics. Investigational agents that bind PBP 2a at low concentrations appear promising but have not been tested in humans. Alternatives to vancomycin are few due to the multiple drug resistances typical of methicillin-resistant staphylococci.
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Affiliation(s)
- H F Chambers
- Medical Service, San Francisco General Hospital 94143, USA.
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45
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Ton-That H, Faull KF, Schneewind O. Anchor structure of staphylococcal surface proteins. A branched peptide that links the carboxyl terminus of proteins to the cell wall. J Biol Chem 1997; 272:22285-92. [PMID: 9268378 DOI: 10.1074/jbc.272.35.22285] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Surface proteins of Staphylococcus aureus are anchored to the cell wall by a mechanism requiring a COOH-terminal sorting signal. Previous work demonstrated that the sorting signal is cleaved at the conserved LPXTG motif and that the carboxyl of threonine (T) is linked to the staphylococcal cell wall. By employing different cell wall lytic enzymes, surface proteins were released from the staphylococcal peptidoglycan and their COOH-terminal anchor structure was revealed by a combination of mass spectrometry and chemical analysis. The results demonstrate that surface proteins are linked to a branched peptide (NH2-Ala-gamma-Gln-Lys-(NH2-Gly5)-Ala-COOH) by an amide bond between the carboxyl of threonine and the amino of the pentaglycine cross-bridge that is attached to the epsilon-amino of lysyl. This branched anchor peptide is amide-linked to the carboxyl of N-acetylmuramic acid, thereby tethering the COOH-terminal end of surface proteins to the staphylococcal peptidoglycan.
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Affiliation(s)
- H Ton-That
- Department of Microbiology & Immunology and Molecular Biology Institute, UCLA School of Medicine, Los Angeles, California 90095, USA
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46
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Xu N, Huang ZH, de Jonge BL, Gage DA. Structural characterization of peptidoglycan muropeptides by matrix-assisted laser desorption ionization mass spectrometry and postsource decay analysis. Anal Biochem 1997; 248:7-14. [PMID: 9177719 DOI: 10.1006/abio.1997.2073] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In this study we report the development of matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS)-based methods for the structural characterization of muropeptides derived from peptidoglycan. Prior to analysis, peptidoglycan samples were subjected to enzymatic digestion with muramidase and the resulting muropeptides were purified by HPLC. A new matrix, 5-chloro-2-mercaptobenzothiazole, was employed for the MALDI-MS analysis. The results have demonstrated that sub-picomole to femtomole detection can be achieved in both positive mode and negative mode, allowing unambiguous determination of the molecular masses of monomeric and oligomeric muropeptides. Structural information from monomeric muropeptides was obtained by further postsource decay (PSD) analysis. Fragmentation patterns in positive mode and negative mode PSD were complementary for the elucidation of the peptide chain sequence. Lysostaphin digestion was also incorporated with MALDI mass mapping analysis for determination of peptide chain cross-linking patterns of muropeptide oligomers from Staphylococcus aureus strains.
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Affiliation(s)
- N Xu
- Department of Biochemistry, Michigan State University, East Lansing 48824, USA
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Abstract
The continuously high prevalence of methicillin-resistant staphylococci (MRS) throughout the world is a constant threat to public health, owing to the multiresistant characteristics of these bacteria. Methicillin resistance is phenotypically associated with the presence of the penicillin-binding protein 2a (PBP2a) not present in susceptible staphylococci. This protein has a low binding affinity for beta-lactam antibiotics. It is a transpeptidase which may take over cell wall synthesis during antibiotic treatment when normally occurring PBPs are inactivated by ligating beta-lactams. PBP2a is encoded by the mecA gene, which is located in mec, a foreign DNA region. Expression of PBP2a is regulated by proteins encoded by the plasmid-borne blaR1-bla1 inducer-repressor system and the corresponding genomic mecRl-mecl system. The blaRl-blal products are important both for the regulation of beta-lactamase and for mecA expression. Methicillin resistance is influenced by a number of additional factors, e.g. the products of the chromosomal fem genes which are important in the synthesis of normal peptidoglycan precursor molecules. Inactivation of fem-genes results in structurally deficient precursors which are not accepted as cell wall building blocks by the ligating PBP2a transpeptidase during antibiotic treatment. This may result in reduced resistance to beta-lactam antibiotics. Inactivation of genes affecting autolysis has shown that autolytic enzymes are also of importance in the expression of methicillin resistance. Methicillin resistance has evolved among earth microorganisms for protection against exogenous or endogenous antibiotics. Presumably the mec region was originally transferred from coagulase negative staphylococci (CNS) to Staphylococcus aureus (SA). A single or a few events of this kind with little subsequent interspecies transfer had been anticipated. However, recent data suggest a continuous horizontal acquisition by S. aureus of mec, being unidirectional from CNS to SA. Methicillin resistance may also be associated with mechanisms independent of mecA, resulting in borderline methicillin resistance. These mechanisms include beta-lactamase hyperproduction, production of methicillinases, acquisition of structurally modified normal PBPs, or the appearance of small colony variants of SA. Most MRS are multiresistant, and the mec region may harbour several resistance determinants, resulting in a clustering of resistance genes within this region.
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Atrih A, Zöllner P, Allmaier G, Foster SJ. Structural analysis of Bacillus subtilis 168 endospore peptidoglycan and its role during differentiation. J Bacteriol 1996; 178:6173-83. [PMID: 8892816 PMCID: PMC178487 DOI: 10.1128/jb.178.21.6173-6183.1996] [Citation(s) in RCA: 121] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The structure of the endospore cell wall peptidoglycan of Bacillus subtilis has been examined. Spore peptidoglycan was produced by the development of a method based on chemical permeabilization of the spore coats and enzymatic hydrolysis of the peptidoglycan. The resulting muropeptides which were >97% pure were analyzed by reverse-phase high-performance liquid chromatography, amino acid analysis, and mass spectrometry. This revealed that 49% of the muramic acid residues in the glycan backbone were present in the delta-lactam form which occurred predominantly every second muramic acid. The glycosidic bonds adjacent to the muramic acid delta-lactam residues were resistant to the action of muramidases. Of the muramic acid residues, 25.7 and 23.3% were substituted with a tetrapeptide and a single L-alanine, respectively. Only 2% of the muramic acids had tripeptide side chains and may constitute the primordial cell wall, the remainder of the peptidoglycan being spore cortex. The spore peptidoglycan is very loosely cross-linked at only 2.9% of the muramic acid residues, a figure approximately 11-fold less than that of the vegetative cell wall. The peptidoglycan from strain AA110 (dacB) had fivefold-greater cross-linking (14.4%) than the wild type and an altered ratio of muramic acid substituents having 37.0, 46.3, and 12.3% delta-lactam, tetrapeptide, and single L-alanine, respectively. This suggests a role for the DacB protein (penicillin-binding protein 5*) in cortex biosynthesis. The sporulation-specific putative peptidoglycan hydrolase CwlD plays a pivotal role in the establishment of the mature spore cortex structure since strain AA107 (cwlD) has spore peptidoglycan which is completely devoid of muramic acid delta-lactam residues. Despite this drastic change in peptidoglycan structure, the spores are still stable but are unable to germinate. The role of delta-lactam and other spore peptidoglycan structural features in the maintenance of dormancy, heat resistance, and germination is discussed.
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Affiliation(s)
- A Atrih
- Department of Molecular Biology and Biotechnology, University of Sheffield, United Kingdom
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Johnson S, Krüger D, Labischinski H. FemA of Staphylococcus aureus: isolation and immunodetection. FEMS Microbiol Lett 1995; 132:221-8. [PMID: 7590176 DOI: 10.1111/j.1574-6968.1995.tb07837.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
FemA, a cytoplasmic protein necessary for the expression of methicillin resistance in Staphylococcus aureus and also involved in the biosynthesis of staphylococcal cell walls, was detected and quantified in several S. aureus strains under different growth conditions by Western immunoblot. Two types of antigens were used for the production of polyclonal antibodies against FemA: (i) a synthetic peptide comprising 14 amino acids of its C-terminal sequence; and (ii) FemA isolated by preparative gel electrophoresis and electroelution from an overproducing staphylococcal strain. Immunodetection revealed that all investigated strains, either methicillin-resistant or susceptible, expressed FemA during the exponential growth phase in varying amounts. In the stationary phase, the FemA content was diminished. Strains in which femA was inactivated by insertion of Tn551 into the control region of the femAB operon still expressed about 10% of the protein compared to their parent strains. Tn551 insertion in the middle of the femB gene did not affect the FemA expression. In 40 methicillin-susceptible and 6 resistant clinical isolates of S. aureus, the FemA content or its affinity to the antibodies was reduced compared to laboratory parent strains. In susceptible strains, an additional protein of higher molecular weight, present in large quantities, was also able to bind the FemA antibodies. Such a protein was also present in methicillin-resistant isolates, although it was not as pronounced as in the susceptible strains.
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Affiliation(s)
- S Johnson
- Robert Koch-Institute, Berlin, Germany
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50
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Vijaranakul U, Nadakavukaren MJ, de Jonge BL, Wilkinson BJ, Jayaswal RK. Increased cell size and shortened peptidoglycan interpeptide bridge of NaCl-stressed Staphylococcus aureus and their reversal by glycine betaine. J Bacteriol 1995; 177:5116-21. [PMID: 7665491 PMCID: PMC177291 DOI: 10.1128/jb.177.17.5116-5121.1995] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Staphylococcus aureus cells grown in a defined medium under conditions of high ionic stress (2.5 M NaCl) were significantly larger than cells grown under unstressed conditions, even though the cells grew much more slowly under stressed conditions. Analysis of the structure of peptidoglycan from stressed cells showed a shorter interpeptide bridge than in peptidoglycan from unstressed cells. Glycine betaine inclusion in the high-NaCl medium resulted in cells with sizes and interpeptide bridges similar to those of cells grown under unstressed conditions.
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Affiliation(s)
- U Vijaranakul
- Department of Biological Sciences, Illinois State University, Normal 61790-4120, USA
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