1
|
Schultz BJ, Snow ED, Walker S. Mechanism of D-alanine transfer to teichoic acids shows how bacteria acylate cell envelope polymers. Nat Microbiol 2023; 8:1318-1329. [PMID: 37308592 PMCID: PMC10664464 DOI: 10.1038/s41564-023-01411-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 05/17/2023] [Indexed: 06/14/2023]
Abstract
Bacterial cell envelope polymers are often modified with acyl esters that modulate physiology, enhance pathogenesis and provide antibiotic resistance. Here, using the D-alanylation of lipoteichoic acid (Dlt) pathway as a paradigm, we have identified a widespread strategy for how acylation of cell envelope polymers occurs. In this strategy, a membrane-bound O-acyltransferase (MBOAT) protein transfers an acyl group from an intracellular thioester onto the tyrosine of an extracytoplasmic C-terminal hexapeptide motif. This motif shuttles the acyl group to a serine on a separate transferase that moves the cargo to its destination. In the Dlt pathway, here studied in Staphylococcus aureus and Streptococcus thermophilus, the C-terminal 'acyl shuttle' motif that forms the crucial pathway intermediate is found on a transmembrane microprotein that holds the MBOAT protein and the other transferase together in a complex. In other systems, found in both Gram-negative and Gram-positive bacteria as well as some archaea, the motif is fused to the MBOAT protein, which interacts directly with the other transferase. The conserved chemistry uncovered here is widely used for acylation throughout the prokaryotic world.
Collapse
Affiliation(s)
- Bailey J Schultz
- Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Eric D Snow
- Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Suzanne Walker
- Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
| |
Collapse
|
2
|
Newman KE, Tindall SN, Mader SL, Khalid S, Thomas GH, Van Der Woude MW. A novel fold for acyltransferase-3 (AT3) proteins provides a framework for transmembrane acyl-group transfer. eLife 2023; 12:e81547. [PMID: 36630168 PMCID: PMC9833829 DOI: 10.7554/elife.81547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 12/04/2022] [Indexed: 01/12/2023] Open
Abstract
Acylation of diverse carbohydrates occurs across all domains of life and can be catalysed by proteins with a membrane bound acyltransferase-3 (AT3) domain (PF01757). In bacteria, these proteins are essential in processes including symbiosis, resistance to viruses and antimicrobials, and biosynthesis of antibiotics, yet their structure and mechanism are largely unknown. In this study, evolutionary co-variance analysis was used to build a computational model of the structure of a bacterial O-antigen modifying acetyltransferase, OafB. The resulting structure exhibited a novel fold for the AT3 domain, which molecular dynamics simulations demonstrated is stable in the membrane. The AT3 domain contains 10 transmembrane helices arranged to form a large cytoplasmic cavity lined by residues known to be essential for function. Further molecular dynamics simulations support a model where the acyl-coA donor spans the membrane through accessing a pore created by movement of an important loop capping the inner cavity, enabling OafB to present the acetyl group close to the likely catalytic resides on the extracytoplasmic surface. Limited but important interactions with the fused SGNH domain in OafB are identified, and modelling suggests this domain is mobile and can both accept acyl-groups from the AT3 and then reach beyond the membrane to reach acceptor substrates. Together this new general model of AT3 function provides a framework for the development of inhibitors that could abrogate critical functions of bacterial pathogens.
Collapse
Affiliation(s)
- Kahlan E Newman
- School of Chemistry, University of SouthamptonSouthamptonUnited Kingdom
| | - Sarah N Tindall
- Department of Biology and the York Biomedical Research Institute, University of YorkYorkUnited Kingdom
| | - Sophie L Mader
- Department of Biochemistry, University of OxfordOxfordUnited Kingdom
| | - Syma Khalid
- Department of Biochemistry, University of OxfordOxfordUnited Kingdom
| | - Gavin H Thomas
- Department of Biology and the York Biomedical Research Institute, University of YorkYorkUnited Kingdom
| | - Marjan W Van Der Woude
- Hull York Medical School and the York Biomedical Research Institute, University of YorkYorkUnited Kingdom
| |
Collapse
|
3
|
Pearson C, Tindall S, Potts JR, Thomas GH, van der Woude MW. Diverse functions for acyltransferase-3 proteins in the modification of bacterial cell surfaces. Microbiology (Reading) 2022; 168. [PMID: 35253642 PMCID: PMC9558356 DOI: 10.1099/mic.0.001146] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The acylation of sugars, most commonly via acetylation, is a widely used mechanism in bacteria that uses a simple chemical modification to confer useful traits. For structures like lipopolysaccharide, capsule and peptidoglycan, that function outside of the cytoplasm, their acylation during export or post-synthesis requires transport of an activated acyl group across the membrane. In bacteria this function is most commonly linked to a family of integral membrane proteins – acyltransferase-3 (AT3). Numerous studies examining production of diverse extracytoplasmic sugar-containing structures have identified roles for these proteins in O-acylation. Many of the phenotypes conferred by the action of AT3 proteins influence host colonisation and environmental survival, as well as controlling the properties of biotechnologically important polysaccharides and the modification of antibiotics and antitumour drugs by Actinobacteria. Herein we present the first systematic review, to our knowledge, of the functions of bacterial AT3 proteins, revealing an important protein family involved in a plethora of systems of importance to bacterial function that is still relatively poorly understood at the mechanistic level. By defining and comparing this set of functions we draw out common themes in the structure and mechanism of this fascinating family of membrane-bound enzymes, which, due to their role in host colonisation in many pathogens, could offer novel targets for the development of antimicrobials.
Collapse
Affiliation(s)
| | - Sarah Tindall
- Department of Biology, University of York, Heslington, UK
| | | | - Gavin H. Thomas
- Department of Biology, University of York, Heslington, UK
- York Biomedical Institute, University of York, Heslington, UK
| | - Marjan W. van der Woude
- Hull York Medical School, Heslington, UK
- York Biomedical Institute, University of York, Heslington, UK
| |
Collapse
|
4
|
Mechanism of Staphylococcus aureus peptidoglycan O-acetyltransferase A as an O-acyltransferase. Proc Natl Acad Sci U S A 2021; 118:2103602118. [PMID: 34480000 DOI: 10.1073/pnas.2103602118] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 07/23/2021] [Indexed: 01/05/2023] Open
Abstract
The O-acetylation of exopolysaccharides, including the essential bacterial cell wall polymer peptidoglycan, confers resistance to their lysis by exogenous hydrolases. Like the enzymes catalyzing the O-acetylation of exopolysaccharides in the Golgi of animals and fungi, peptidoglycan O-acetyltransferase A (OatA) is predicted to be an integral membrane protein comprised of a membrane-spanning acyltransferase-3 (AT-3) domain and an extracytoplasmic domain; for OatA, these domains are located in the N- and C-terminal regions of the enzyme, respectively. The recombinant C-terminal domain (OatAC) has been characterized as an SGNH acetyltransferase, but nothing was known about the function of the N-terminal AT-3 domain (OatAN) or its homologs associated with other acyltransferases. We report herein the experimental determination of the topology of Staphylococcus aureus OatAN, which differs markedly from that predicted in silico. We present the biochemical characterization of OatAN as part of recombinant OatA and demonstrate that acetyl-CoA serves as the substrate for OatAN Using in situ and in vitro assays, we characterized 35 engineered OatA variants which identified a catalytic triad of Tyr-His-Glu residues. We trapped an acetyl group from acetyl-CoA on the catalytic Tyr residue that is located on an extracytoplasmic loop of OatAN Further enzymatic characterization revealed that O-acetyl-Tyr represents the substrate for OatAC We propose a model for OatA action involving the translocation of acetyl groups from acetyl-CoA across the cytoplasmic membrane by OatAN and their subsequent intramolecular transfer to OatAC for the O-acetylation of peptidoglycan via the concerted action of catalytic Tyr and Ser residues.
Collapse
|
5
|
Varghese R, Veeraraghavan B. Decoding the Penicillin Resistance of Streptococcus pneumoniae for Invasive and Noninvasive Infections. Microb Drug Resist 2021; 27:942-950. [DOI: 10.1089/mdr.2020.0233] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Rosemol Varghese
- Department of Clinical Microbiology, Christian Medical College, Vellore, India
| | | |
Collapse
|
6
|
Straume D, Piechowiak KW, Kjos M, Håvarstein LS. Class A PBPs: It is time to rethink traditional paradigms. Mol Microbiol 2021; 116:41-52. [PMID: 33709487 DOI: 10.1111/mmi.14714] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 03/08/2021] [Accepted: 03/09/2021] [Indexed: 12/18/2022]
Abstract
Until recently, class A penicillin-binding proteins (aPBPs) were the only enzymes known to catalyze glycan chain polymerization from lipid II in bacteria. Hence, the discovery of two novel lipid II polymerases, FtsW and RodA, raises new questions and has consequently received a lot of attention from the research community. FtsW and RodA are essential and highly conserved members of the divisome and elongasome, respectively, and work in conjunction with their cognate class B PBPs (bPBPs) to synthesize the division septum and insert new peptidoglycan into the lateral cell wall. The identification of FtsW and RodA as peptidoglycan glycosyltransferases has raised questions regarding the role of aPBPs in peptidoglycan synthesis and fundamentally changed our understanding of the process. Despite their dethronement, aPBPs are essential in most bacteria. So, what is their function? In this review, we discuss recent progress in answering this question and present our own views on the topic.
Collapse
Affiliation(s)
- Daniel Straume
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, Norway
| | | | - Morten Kjos
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, Norway
| | - Leiv Sigve Håvarstein
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, Norway
| |
Collapse
|
7
|
MacCain WJ, Tuomanen EI. Mini-Review: Bioactivities of Bacterial Cell Envelopes in the Central Nervous System. Front Cell Infect Microbiol 2020; 10:588378. [PMID: 33194834 PMCID: PMC7649116 DOI: 10.3389/fcimb.2020.588378] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 09/16/2020] [Indexed: 11/21/2022] Open
Abstract
During acute bacterial meningitis, recognition of the bacterial envelope by immune cells of the central nervous system (CNS) generates a robust response that is essential to clear bacteria. This response is further amplified during treatment when lytic antibiotics, required for cure, also generate a burst of highly inflammatory cell envelope debris. Different peptidoglycan (PG) subcomponents interact with neurons, glia, and the blood brain barrier resulting in the entire symptom complex of meningitis. Recently, this CNS-cell envelope signaling axis has been extended to non-inflammatory recognition of cell wall components circulating from endogenous bacteria to the brain resulting in both benefit and chronic damage. This review will describe the molecular details of a broad array of cell envelope-induced responses in the CNS and what current strategies can be implemented to improve clinical outcome.
Collapse
Affiliation(s)
- William J MacCain
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN, United States
| | - Elaine I Tuomanen
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN, United States
| |
Collapse
|
8
|
Assoni L, Milani B, Carvalho MR, Nepomuceno LN, Waz NT, Guerra MES, Converso TR, Darrieux M. Resistance Mechanisms to Antimicrobial Peptides in Gram-Positive Bacteria. Front Microbiol 2020; 11:593215. [PMID: 33193264 PMCID: PMC7609970 DOI: 10.3389/fmicb.2020.593215] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 09/03/2020] [Indexed: 02/06/2023] Open
Abstract
With the alarming increase of infections caused by pathogenic multidrug-resistant bacteria over the last decades, antimicrobial peptides (AMPs) have been investigated as a potential treatment for those infections, directly through their lytic effect or indirectly, due to their ability to modulate the immune system. There are still concerns regarding the use of such molecules in the treatment of infections, such as cell toxicity and host factors that lead to peptide inhibition. To overcome these limitations, different approaches like peptide modification to reduce toxicity and peptide combinations to improve therapeutic efficacy are being tested. Human defense peptides consist of an important part of the innate immune system, against a myriad of potential aggressors, which have in turn developed different ways to overcome the AMPs microbicidal activities. Since the antimicrobial activity of AMPs vary between Gram-positive and Gram-negative species, so do the bacterial resistance arsenal. This review discusses the mechanisms exploited by Gram-positive bacteria to circumvent killing by antimicrobial peptides. Specifically, the most clinically relevant genera, Streptococcus spp., Staphylococcus spp., Enterococcus spp. and Gram-positive bacilli, have been explored.
Collapse
Affiliation(s)
- Lucas Assoni
- Laboratório de Biologia Molecular de Microrganismos, Universidade São Francisco, Bragança Paulista, Brazil
| | - Barbara Milani
- Laboratório de Biologia Molecular de Microrganismos, Universidade São Francisco, Bragança Paulista, Brazil
| | - Marianna Ribeiro Carvalho
- Laboratório de Biologia Molecular de Microrganismos, Universidade São Francisco, Bragança Paulista, Brazil
| | - Lucas Natanael Nepomuceno
- Laboratório de Biologia Molecular de Microrganismos, Universidade São Francisco, Bragança Paulista, Brazil
| | - Natalha Tedeschi Waz
- Laboratório de Biologia Molecular de Microrganismos, Universidade São Francisco, Bragança Paulista, Brazil
| | - Maria Eduarda Souza Guerra
- Laboratório de Biologia Molecular de Microrganismos, Universidade São Francisco, Bragança Paulista, Brazil
| | - Thiago Rojas Converso
- Laboratório de Biologia Molecular de Microrganismos, Universidade São Francisco, Bragança Paulista, Brazil
| | - Michelle Darrieux
- Laboratório de Biologia Molecular de Microrganismos, Universidade São Francisco, Bragança Paulista, Brazil
| |
Collapse
|
9
|
Acetylation of Surface Carbohydrates in Bacterial Pathogens Requires Coordinated Action of a Two-Domain Membrane-Bound Acyltransferase. mBio 2020; 11:mBio.01364-20. [PMID: 32843546 PMCID: PMC7448272 DOI: 10.1128/mbio.01364-20] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Acyltransferase-3 (AT3) domain-containing membrane proteins are involved in O-acetylation of a diverse range of carbohydrates across all domains of life. In bacteria they are essential in processes including symbiosis, resistance to antimicrobials, and biosynthesis of antibiotics. Their mechanism of action, however, is poorly characterized. We analyzed two acetyltransferases as models for this important family of membrane proteins, which modify carbohydrates on the surface of the pathogen Salmonella enterica, affecting immunogenicity, virulence, and bacteriophage resistance. We show that when these AT3 domains are fused to a periplasmic partner domain, both domains are required for substrate acetylation. The data show conserved elements in the AT3 domain and unique structural features of the periplasmic domain. Our data provide a working model to probe the mechanism and function of the diverse and important members of the widespread AT3 protein family, which are required for biologically significant modifications of cell-surface carbohydrates. Membrane bound acyltransferase-3 (AT3) domain-containing proteins are implicated in a wide range of carbohydrate O-acyl modifications, but their mechanism of action is largely unknown. O-antigen acetylation by AT3 domain-containing acetyltransferases of Salmonella spp. can generate a specific immune response upon infection and can influence bacteriophage interactions. This study integrates in situ and in vitro functional analyses of two of these proteins, OafA and OafB (formerly F2GtrC), which display an “AT3-SGNH fused” domain architecture, where an integral membrane AT3 domain is fused to an extracytoplasmic SGNH domain. An in silico-inspired mutagenesis approach of the AT3 domain identified seven residues which are fundamental for the mechanism of action of OafA, with a particularly conserved motif in TMH1 indicating a potential acyl donor interaction site. Genetic and in vitro evidence demonstrate that the SGNH domain is both necessary and sufficient for lipopolysaccharide acetylation. The structure of the periplasmic SGNH domain of OafB identified features not previously reported for SGNH proteins. In particular, the periplasmic portion of the interdomain linking region is structured. Significantly, this region constrains acceptor substrate specificity, apparently by limiting access to the active site. Coevolution analysis of the two domains suggests possible interdomain interactions. Combining these data, we propose a refined model of the AT3-SGNH proteins, with structurally constrained orientations of the two domains. These findings enhance our understanding of how cells can transfer acyl groups from the cytoplasm to specific extracellular carbohydrates.
Collapse
|
10
|
Jones CS, Sychantha D, Howell PL, Clarke AJ. Structural basis for the O-acetyltransferase function of the extracytoplasmic domain of OatA from Staphylococcus aureus. J Biol Chem 2020; 295:8204-8213. [PMID: 32350117 DOI: 10.1074/jbc.ra120.013108] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 04/27/2020] [Indexed: 02/03/2023] Open
Abstract
Many bacteria possess enzymes that modify the essential cell-wall polymer peptidoglycan by O-acetylation. This modification occurs in numerous Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus, a common cause of human infections. O-Acetylation of peptidoglycan protects bacteria from the lytic activity of lysozyme, a mammalian innate immune enzyme, and as such is important for bacterial virulence. The O-acetylating enzyme in Gram-positive bacteria, O-acetyltransferase A (OatA), is a two-domain protein consisting of an N-terminal integral membrane domain and a C-terminal extracytoplasmic domain. Here, we present the X-ray crystal structure at 1.71 Å resolution and the biochemical characterization of the C-terminal domain of S. aureus OatA. The structure revealed that this OatA domain adopts an SGNH-hydrolase fold and possesses a canonical catalytic triad. Site-specific replacement of active-site amino acids revealed the presence of a water-coordinating aspartate residue that limits esterase activity. This residue, although conserved in staphyloccocal OatA and most other homologs, is not present in the previously characterized streptococcal OatA. These results provide insights into the mechanism of acetyl transfer in the SGNH/GDSL hydrolase family and highlight important evolutionary differences between homologous OatA enzymes. Furthermore, this study enhances our understanding of PG O-acetyltransferases, which could guide the development of novel antibacterial drugs to combat infections with multidrug-resistant bacterial pathogens.
Collapse
Affiliation(s)
- Carys S Jones
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - David Sychantha
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - P Lynne Howell
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Biochemistry, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Anthony J Clarke
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada .,Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario, Canada
| |
Collapse
|
11
|
Genetic Determinants Enabling Medium-Dependent Adaptation to Nafcillin in Methicillin-Resistant Staphylococcus aureus. mSystems 2020; 5:5/2/e00828-19. [PMID: 32234776 PMCID: PMC7112963 DOI: 10.1128/msystems.00828-19] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antimicrobial susceptibility testing standards driving clinical decision-making have centered around the use of cation-adjusted Mueller-Hinton broth (CA-MHB) as the medium with the notion of supporting bacterial growth, without consideration of recapitulating the in vivo environment. However, it is increasingly recognized that various medium conditions have tremendous influence on antimicrobial activity, which in turn may have major implications on the ability of in vitro susceptibility assays to predict antibiotic activity in vivo. To elucidate differential growth optimization and antibiotic resistance mechanisms, adaptive laboratory evolution was performed in the presence or absence of the antibiotic nafcillin with methicillin-resistant Staphylococcus aureus (MRSA) TCH1516 in either (i) CA-MHB, a traditional bacteriological nutritionally rich medium, or (ii) Roswell Park Memorial Institute (RPMI), a medium more reflective of the in vivo host environment. Medium adaptation analysis showed an increase in growth rate in RPMI, but not CA-MHB, with mutations in apt, adenine phosphoribosyltransferase, and the manganese transporter subunit, mntA, occurring reproducibly in parallel replicate evolutions. The medium-adapted strains showed no virulence attenuation. Continuous exposure of medium-adapted strains to increasing concentrations of nafcillin led to medium-specific evolutionary strategies. Key reproducibly occurring mutations were specific for nafcillin adaptation in each medium type and did not confer resistance in the other medium environment. Only the vraRST operon, a regulator of membrane- and cell wall-related genes, showed mutations in both CA-MHB- and RPMI-evolved strains. Collectively, these results demonstrate the medium-specific genetic adaptive responses of MRSA and establish adaptive laboratory evolution as a platform to study clinically relevant resistance mechanisms.IMPORTANCE The ability of pathogens such as Staphylococcus aureus to evolve resistance to antibiotics used in the treatment of infections has been an important concern in the last decades. Resistant acquisition usually translates into treatment failure and puts patients at risk of unfavorable outcomes. Furthermore, the laboratory testing of antibiotic resistance does not account for the different environment the bacteria experiences within the human body, leading to results that do not translate into the clinic. In this study, we forced methicillin-resistant S. aureus to develop nafcillin resistance in two different environments, a laboratory environment and a physiologically more relevant environment. This allowed us to identify genetic changes that led to nafcillin resistance under both conditions. We concluded that not only does the environment dictate the evolutionary strategy of S. aureus to nafcillin but also that the evolutionary strategy is specific to that given environment.
Collapse
|
12
|
Class A PBPs have a distinct and unique role in the construction of the pneumococcal cell wall. Proc Natl Acad Sci U S A 2020; 117:6129-6138. [PMID: 32123104 PMCID: PMC7084106 DOI: 10.1073/pnas.1917820117] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Peptidoglycan, the main structural component of the bacterial cell wall, is made of glycan strands cross-linked by short peptides. It has long been assumed that class A penicillin-binding proteins (PBPs) are the only enzymes capable of synthesizing glycan strands from lipid II. Recently, however, it was discovered that two non-PBP proteins, FtsW and RodA, constitute the core peptidoglycan polymerizing enzymes of the divisome and elongasome, respectively. What, then, is the role of class A PBPs in the construction of the bacterial cell wall? In contrast to previous assumptions, our results strongly suggest that class A PBPs are not an intrinsic part of the divisome and elongasome but have important autonomous roles in construction of the fully mature bacterial cell wall. In oval-shaped Streptococcus pneumoniae, septal and longitudinal peptidoglycan syntheses are performed by independent functional complexes: the divisome and the elongasome. Penicillin-binding proteins (PBPs) were long considered the key peptidoglycan-synthesizing enzymes in these complexes. Among these were the bifunctional class A PBPs, which are both glycosyltransferases and transpeptidases, and monofunctional class B PBPs with only transpeptidase activity. Recently, however, it was established that the monofunctional class B PBPs work together with transmembrane glycosyltransferases (FtsW and RodA) from the shape, elongation, division, and sporulation (SEDS) family to make up the core peptidoglycan-synthesizing machineries within the pneumococcal divisome (FtsW/PBP2x) and elongasome (RodA/PBP2b). The function of class A PBPs is therefore now an open question. Here we utilize the peptidoglycan hydrolase CbpD that targets the septum of S. pneumoniae cells to show that class A PBPs have an autonomous role during pneumococcal cell wall synthesis. Using assays to specifically inhibit the function of PBP2x and FtsW, we demonstrate that CbpD attacks nascent peptidoglycan synthesized by the divisome. Notably, class A PBPs could process this nascent peptidoglycan from a CbpD-sensitive to a CbpD-resistant form. The class A PBP-mediated processing was independent of divisome and elongasome activities. Class A PBPs thus constitute an autonomous functional entity which processes recently formed peptidoglycan synthesized by FtsW/PBP2×. Our results support a model in which mature pneumococcal peptidoglycan is synthesized by three functional entities, the divisome, the elongasome, and bifunctional PBPs. The latter modify existing peptidoglycan but are probably not involved in primary peptidoglycan synthesis.
Collapse
|
13
|
Liang J, Mantelos A, Toh ZQ, Tortorella SM, Ververis K, Vongsvivut J, Bambery KR, Licciardi PV, Hung A, Karagiannis TC. Investigation of potential anti-pneumococcal effects of l-sulforaphane and metabolites: Insights from synchrotron-FTIR microspectroscopy and molecular docking studies. J Mol Graph Model 2020; 97:107568. [PMID: 32097886 DOI: 10.1016/j.jmgm.2020.107568] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 02/10/2020] [Indexed: 01/06/2023]
Abstract
Streptococcus pneumoniae infection can lead to pneumococcal disease, a major cause of mortality in children under the age of five years. In low- and middle-income country settings where pneumococcal disease burden is high, vaccine use is low and widespread antibiotic use has led to increased rates of multi-drug resistant pneumococci. l-sulforaphane (LSF), derived from broccoli and other cruciferous vegetables, has established anti-inflammatory, antioxidant, and anti-microbial properties. Hence, we sought to investigate the potential role of LSF against pneumococcal infection. Using a combination of in vitro and computational methods, the results showed that LSF and relevant metabolites had a potential to reduce pneumococcal adherence through modulation of host receptors, regulation of inflammation, or through direct modification of bacterial factors. Treatment with LSF and metabolites reduced pneumococcal adherence to respiratory epithelial cells. Synchrotron-Fourier transform infrared microspectroscopy (S-FTIR) revealed biochemical changes in protein and lipid profiles of lung epithelial cells following treatment with LSF or metabolites. Molecular docking studies of 116 pneumococcal and 89 host factors revealed a potent effect for the metabolite LSF-glutathione (GSH). A comprehensive list of factors involved in interactions between S. pneumoniae and host cells was compiled to construct a bacterium and host interaction network. Network analysis revealed plasminogen, fibronectin, and RrgA as key factors involved in pneumococcal-host interactions. Therefore, we propose that these constitute critical targets for direct inhibition by LSF and/or metabolites, which may disrupt pneumococcal-host adherence. Overall, our findings further enhance understanding of the potential role of LSF to modulate pneumococcal-host dynamics.
Collapse
Affiliation(s)
- Julia Liang
- Epigenomic Medicine, Department of Diabetes, Central Clinical School, Monash University, Melbourne, VIC, 3004, Australia; School of Science, RMIT University, VIC, 3001, Australia
| | - Anita Mantelos
- Epigenomic Medicine, Department of Diabetes, Central Clinical School, Monash University, Melbourne, VIC, 3004, Australia; Murdoch Children's Research Institute, Melbourne, Parkville, VIC, 3052, Australia; Department of Paediatrics, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Zheng Quan Toh
- Murdoch Children's Research Institute, Melbourne, Parkville, VIC, 3052, Australia
| | - Stephanie M Tortorella
- Epigenomic Medicine, Department of Diabetes, Central Clinical School, Monash University, Melbourne, VIC, 3004, Australia
| | - Katherine Ververis
- Epigenomic Medicine, Department of Diabetes, Central Clinical School, Monash University, Melbourne, VIC, 3004, Australia
| | | | - Keith R Bambery
- ANSTO Australian Synchrotron, 800 Blackburn Road, Clayton, VIC, 3168, Australia
| | - Paul V Licciardi
- Murdoch Children's Research Institute, Melbourne, Parkville, VIC, 3052, Australia; Department of Paediatrics, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Andrew Hung
- School of Science, RMIT University, VIC, 3001, Australia
| | - Tom C Karagiannis
- Epigenomic Medicine, Department of Diabetes, Central Clinical School, Monash University, Melbourne, VIC, 3004, Australia; Department of Clinical Pathology, The University of Melbourne, Parkville, VIC, 3052, Australia.
| |
Collapse
|
14
|
Brott AS, Clarke AJ. Peptidoglycan O-Acetylation as a Virulence Factor: Its Effect on Lysozyme in the Innate Immune System. Antibiotics (Basel) 2019; 8:antibiotics8030094. [PMID: 31323733 PMCID: PMC6783866 DOI: 10.3390/antibiotics8030094] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 07/11/2019] [Accepted: 07/13/2019] [Indexed: 11/16/2022] Open
Abstract
The peptidoglycan sacculus of both Gram-positive and Gram-negative bacteria acts as a protective mesh and provides structural support around the entirety of the cell. The integrity of this structure is of utmost importance for cell viability and so naturally is the first target for attack by the host immune system during bacterial infection. Lysozyme, a muramidase and the first line of defense of the innate immune system, targets the peptidoglycan sacculus hydrolyzing the β-(1→4) linkage between repeating glycan units, causing lysis and the death of the invading bacterium. The O-acetylation of N-acetylmuramoyl residues within peptidoglycan precludes the productive binding of lysozyme, and in doing so renders it inactive. This modification has been shown to be an important virulence factor in pathogens such as Staphylococcus aureus and Neisseria gonorrhoeae and is currently being investigated as a novel target for anti-virulence therapies. This article reviews interactions made between peptidoglycan and the host immune system, specifically with respect to lysozyme, and how the O-acetylation of the peptidoglycan interrupts these interactions, leading to increased pathogenicity.
Collapse
Affiliation(s)
- Ashley S Brott
- Department of Molecular & Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Anthony J Clarke
- Department of Molecular & Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.
| |
Collapse
|
15
|
Porfírio S, Carlson RW, Azadi P. Elucidating Peptidoglycan Structure: An Analytical Toolset. Trends Microbiol 2019; 27:607-622. [DOI: 10.1016/j.tim.2019.01.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 01/16/2019] [Accepted: 01/29/2019] [Indexed: 01/04/2023]
|
16
|
Identification of Pneumococcal Factors Affecting Pneumococcal Shedding Shows that the dlt Locus Promotes Inflammation and Transmission. mBio 2019; 10:mBio.01032-19. [PMID: 31213554 PMCID: PMC6581856 DOI: 10.1128/mbio.01032-19] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Streptococcus pneumoniae (the pneumococcus) is a common cause of respiratory tract and invasive infection. The overall effectiveness of immunization with the organism’s capsular polysaccharide depends on its ability to block colonization of the upper respiratory tract and thereby prevent host-to-host transmission. Because of the limited coverage of current pneumococcal vaccines, we carried out an unbiased in vivo transposon mutagenesis screen to identify pneumococcal factors other than its capsular polysaccharide that affect transmission. One such candidate was expressed by the dlt locus, previously shown to add d-alanine onto the pneumococcal lipoteichoic acid present on the bacterial cell surface. This modification protects against host antimicrobials and augments host inflammatory responses. The latter increases secretions and bacterial shedding from the upper respiratory tract to allow for transmission. Thus, this study provides insight into a mechanism employed by the pneumococcus to successfully transit from one host to another. Host-to-host transmission is a necessary but poorly understood aspect of microbial pathogenesis. Herein, we screened a genomic library of mutants of the leading respiratory pathogen Streptococcus pneumoniae generated by mariner transposon mutagenesis (Tn-Seq) to identify genes contributing to its exit or shedding from the upper respiratory tract (URT), the limiting step in the organism’s transmission in an infant mouse model. Our analysis focused on genes affecting the bacterial surface that directly impact interactions with the host. Among the multiple factors identified was the dlt locus, which adds d-alanine onto lipoteichoic acids (LTA) and thereby increases Toll-like receptor 2-mediated inflammation and resistance to antimicrobial peptides. The more robust proinflammatory response in the presence of d-alanylation promotes secretions that facilitate pneumococcal shedding and allows for transmission. Expression of the dlt locus is controlled by the CiaRH system, which senses cell wall stress in response to antimicrobial activity, including in response to lysozyme, the most abundant antimicrobial along the URT mucosa. Accordingly, in a lysM−/− host, there was no longer an effect of the dlt locus on pneumococcal shedding. Thus, our findings demonstrate how a pathogen senses the URT milieu and then modifies its surface characteristics to take advantage of the host response for transit to another host.
Collapse
|
17
|
Brott AS, Jones CS, Clarke AJ. Development of a High Throughput Screen for the Identification of Inhibitors of Peptidoglycan O-Acetyltransferases, New Potential Antibacterial Targets. Antibiotics (Basel) 2019; 8:E65. [PMID: 31137799 PMCID: PMC6627197 DOI: 10.3390/antibiotics8020065] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 05/22/2019] [Accepted: 05/22/2019] [Indexed: 12/02/2022] Open
Abstract
The O-acetylation of peptidoglycan occurs in many Gram-negative and most Gram-positive pathogens and this modification to the essential wall polymer controls the lytic activity of the autolysins, particularly the lytic transglycosylases, and inhibits that of the lysozymes of innate immunity systems. As such, the peptidoglycan O-acetyltransferases PatA/B and OatA are recognized as virulence factors. In this study, we present the high throughput screening of small compound libraries to identify the first known inhibitors of these enzymes. The fluorometric screening assay developed involved monitoring the respective O-acetyltransferases as esterases using 4-methylumbelliferylacetate as substrate. Pilot screens of 3921 compounds validated the usefulness of the HTS protocol. A number of potential inhibitors were identified amongst a total of 145,000 low molecular-weight compounds, some of which were common to both enzymes, while others were unique to each. After eliminating a number of false positives in secondary screens, dose response curves confirmed the apparent specificity of a benzothiazolyl-pyrazolo-pyridine as an inhibitor of Neisseria gonorrhoeae PatB, and several coumarin-based compounds as inhibitors of both this PatB and OatA from Staphylococcus aureus. The benzothiazolyl-pyrazolo-pyridine was determined to be a non-competitive inhibitor of PatB with a Ki of 126 µM. At 177 µg/mL and close to its solubility limit, this compound caused a 90% reduction in growth of N. gonorrhoeae, while growth of Escherichia coli, a bacterium that lacks PatB and, hence, does not produce O-acetylated peptidoglycan, was unaffected. These data provide preliminary proof of concept that peptidoglycan O-acetyltransferases would serve as useful antibacterial targets.
Collapse
Affiliation(s)
- Ashley S Brott
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.
| | - Carys S Jones
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.
| | - Anthony J Clarke
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.
| |
Collapse
|
18
|
Vollmer W, Massidda O, Tomasz A. The Cell Wall of Streptococcus pneumoniae. Microbiol Spectr 2019; 7:10.1128/microbiolspec.gpp3-0018-2018. [PMID: 31172911 PMCID: PMC11026078 DOI: 10.1128/microbiolspec.gpp3-0018-2018] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Indexed: 12/13/2022] Open
Abstract
Streptococcus pneumoniae has a complex cell wall that plays key roles in cell shape maintenance, growth and cell division, and interactions with components of the human host. The peptidoglycan has a heterogeneous composition with more than 50 subunits (muropeptides)-products of several peptidoglycan-modifying enzymes. The amidation of glutamate residues in the stem peptide is needed for efficient peptide cross-linking, and peptides with a dipeptide branch prevail in some beta-lactam-resistant strains. The glycan strands are modified by deacetylation of N-acetylglucosamine residues and O-acetylation of N-acetylmuramic acid residues, and both modifications contribute to pneumococcal resistance to lysozyme. The glycan strands carry covalently attached wall teichoic acid and capsular polysaccharide. Pneumococci are unique in that the wall teichoic acid and lipoteichoic acid contain the same unusually complex repeating units decorated with phosphoryl choline residues, which anchor the choline-binding proteins. The structures of lipoteichoic acid and the attachment site of wall teichoic acid to peptidoglycan have recently been revised. During growth, pneumococci assemble their cell walls at midcell in coordinated rounds of cell elongation and division, leading to the typical ovococcal cell shape. Cell wall growth depends on the cytoskeletal FtsA and FtsZ proteins and is regulated by several morphogenesis proteins that also show patterns of dynamic localization at midcell. Some of the key regulators are phosphorylated by StkP and dephosphorylated by PhpP to facilitate robust selection of the division site and plane and to maintain cell shape.
Collapse
Affiliation(s)
- Waldemar Vollmer
- Institute for Cell and Molecular Biosciences, The Centre for Bacterial Cell Biology, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Orietta Massidda
- Department of Cellular, Computational and Integrative Biology, University of Trento, Trento, Italy
| | | |
Collapse
|
19
|
Abstract
The genus Streptococcus includes Gram-positive organisms shaped in cocci and organized in chains. They are commensals, pathogens, and opportunistic pathogens for humans and animals. Most Streptococcus species of veterinary relevance have a specific ecological niche, such as S. uberis, which is almost exclusively an environmental pathogen causing bovine mastitis. In contrast, S. suis can be considered as a true zoonotic pathogen, causing specific diseases in humans after contact with infected animals or derived food products. Finally, Streptococcus species such as S. agalactiae can be sporadically zoonotic, even though they are pathogens of both humans and animals independently. For clarification, a short taxonomical overview will be given here to highlight the diversity of streptococci that infect animals. Several families of antibiotics are used to treat animals for streptococcal infections. First-line treatments are penicillins (alone or in combination with aminoglycosides), macrolides and lincosamides, fluoroquinolones, and tetracyclines. Because of the selecting role of antibiotics, resistance phenotypes have been reported in streptococci isolated from animals worldwide. Globally, the dynamic of resistance acquisition in streptococci is slower than what is experienced in Enterobacteriaceae, probably due to the much more limited horizontal spread of resistance genes. Nonetheless, transposons or integrative and conjugative elements can disseminate resistance determinants among streptococci. Besides providing key elements on the prevalence of resistance in streptococci from animals, this article will also largely consider the mechanisms and molecular epidemiology of the major types of resistance to antimicrobials encountered in the most important streptococcal species in veterinary medicine.
Collapse
|
20
|
Sychantha D, Brott AS, Jones CS, Clarke AJ. Mechanistic Pathways for Peptidoglycan O-Acetylation and De-O-Acetylation. Front Microbiol 2018; 9:2332. [PMID: 30327644 PMCID: PMC6174289 DOI: 10.3389/fmicb.2018.02332] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 09/11/2018] [Indexed: 12/22/2022] Open
Abstract
The post-synthetic O-acetylation of the essential component of bacterial cell walls, peptidoglycan (PG), is performed by many pathogenic bacteria to help them evade the lytic action of innate immunity responses. Occurring at the C-6 hydroxyl of N-acetylmuramoyl residues, this modification to the glycan backbone of PG sterically blocks the activity of lysozymes. As such, the enzyme responsible for this modification in Gram-positive bacteria is recognized as a virulence factor. With Gram-negative bacteria, the O-acetylation of PG provides a means of control of their autolysins at the substrate level. In this review, we discuss the pathways for PG O-acetylation and de-O-acetylation and the structure and function relationship of the O-acetyltransferases and O-acetylesterases that catalyze these reactions. The current understanding of their mechanisms of action is presented and the prospects of targeting these systems for the development of novel therapeutics are explored.
Collapse
Affiliation(s)
| | | | | | - Anthony J. Clarke
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada
| |
Collapse
|
21
|
Sychantha D, Clarke AJ. Peptidoglycan Modification by the Catalytic Domain of Streptococcus pneumoniae OatA Follows a Ping-Pong Bi-Bi Mechanism of Action. Biochemistry 2018; 57:2394-2401. [PMID: 29595955 DOI: 10.1021/acs.biochem.8b00301] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Streptococcus pneumoniae among other Gram-positive pathogens produces O-acetylated peptidoglycan using the enzyme OatA. This process occurs through the transfer of an acetyl group from a donor to the hydroxyl group of an acceptor sugar. While it has been established that this process involves the extracellular, catalytic domain of OatA ( SpOatAC), mechanistic insight is still unavailable. This study examined the enzymatic characteristics of SpOatAC-catalyzed reactions through analysis of both pre-steady- and steady-state kinetics. Our findings clearly show that SpOatAC follows a ping-pong bi-bi mechanism of action involving a covalent acetyl-enzyme intermediate. The modified residue was verified to be the catalytic nucleophile, Ser438. The pH dependence of the enzyme kinetics revealed that a single ionizable group is involved, which is consistent with the participation of a His residue. Single-turnover kinetics of esterase activity demonstrated that k2 ≫ k3, revealing that the rate-limiting step for the hydrolytic reaction was the breakdown of the acetyl-enzyme intermediate with a half-life of >1 min. The previous assignment of Asn491 as an oxyanion hole residue was also confirmed as its replacement with Ala resulted in a 50-fold decrease in catalytic efficiency relative to that of wild-type SpOatAC. However, this loss of catalytic efficiency was mostly due to a large increase in KM, suggesting that Asn491 contributes more to substrate binding.
Collapse
Affiliation(s)
- David Sychantha
- Department of Molecular & Cellular Biology , University of Guelph , Guelph , ON N1G 2W1 , Canada
| | - Anthony J Clarke
- Department of Molecular & Cellular Biology , University of Guelph , Guelph , ON N1G 2W1 , Canada
| |
Collapse
|
22
|
Engholm DH, Kilian M, Goodsell DS, Andersen ES, Kjærgaard RS. A visual review of the human pathogen Streptococcus pneumoniae. FEMS Microbiol Rev 2018; 41:854-879. [PMID: 29029129 DOI: 10.1093/femsre/fux037] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 09/04/2017] [Indexed: 11/12/2022] Open
Abstract
Being the principal causative agent of bacterial pneumonia, otitis media, meningitis and septicemia, the bacterium Streptococcus pneumoniae is a major global health problem. To highlight the molecular basis of this problem, we have portrayed essential biological processes of the pneumococcal life cycle in eight watercolor paintings. The paintings are done to a consistent nanometer scale based on currently available data from structural biology and proteomics. In this review article, the paintings are used to provide a visual review of protein synthesis, carbohydrate metabolism, cell wall synthesis, cell division, teichoic acid synthesis, virulence, transformation and pilus synthesis based on the available scientific literature within the field of pneumococcal biology. Visualization of the molecular details of these processes reveals several scientific questions about how molecular components of the pneumococcal cell are organized to allow biological function to take place. By the presentation of this visual review, we intend to stimulate scientific discussion, aid in the generation of scientific hypotheses and increase public awareness. A narrated video describing the biological processes in the context of a whole-cell illustration accompany this article.
Collapse
Affiliation(s)
- Ditte Høyer Engholm
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark
| | - Mogens Kilian
- Department of Biomedicine, Aarhus University, 8000 Aarhus, Denmark
| | - David S Goodsell
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.,Rutgers, the State University of New Jersey, NJ 08901, USA
| | - Ebbe Sloth Andersen
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark.,Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus, Denmark
| | | |
Collapse
|
23
|
Zhong R, Cui D, Ye ZH. Regiospecific Acetylation of Xylan is Mediated by a Group of DUF231-Containing O-Acetyltransferases. PLANT & CELL PHYSIOLOGY 2017; 58:2126-2138. [PMID: 29059346 DOI: 10.1093/pcp/pcx147] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 09/22/2017] [Indexed: 05/27/2023]
Abstract
Xylan is a major hemicellulose in the secondary walls of vessels and fibers, and its acetylation is essential for normal secondary wall assembly and properties. The acetylation of xylan can occur at multiple positions of its backbone xylosyl residues, including 2-O-monoacetylation, 3-O-monoacetylation, 2,3-di-O-acetylation and 3-O-acetylation of 2-O-glucuronic acid (GlcA)-substituted xylosyl residues, but the biochemical mechanism controlling the regiospecific acetylation of xylan is largely unknown. Here, we present biochemical characterization of a group of Arabidopsis thaliana DUF231-containing proteins, namely TBL28, ESK1/TBL29, TBL30, TBL3, TBL31, TBL32, TBL33, TBL34 and TBL35, for their roles in catalyzing the regiospecific acetylation of xylan. Acetyltransferase activity assay of recombinant proteins demonstrated that all of these proteins possessed xylan acetyltransferase activities catalyzing the transfer of acetyl groups from acetyl-CoA onto xylooligomer acceptors albeit with differential specificities. Structural analysis of their reaction products revealed that TBL28, ESK1, TBL3, TBL31 and TBL34 catalyzed xylan 2-O- and 3-O-monoacetylation and 2,3-di-O-acetylation with differential positional preference, TBL30 carried out 2-O- and 3-O-monoacetylation, TBL35 catalyzed 2,3-di-O-acetylation, and TBL32 and TBL33 mediated 3-O-acetylation of 2-O-GlcA-substituted xylosyl residues. Furthermore, mutations of the conserved GDS and DXXH motifs in ESK1 were found to result in a complete loss of its acetyltransferase activity. Together, these results establish that these nine DUF231-containing proteins are xylan acetyltransferases mediating the regiospecific acetylation of xylan and that the conserved GDS and DXXH motifs are critical for their acetyltransferase activity.
Collapse
Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
| | - Dongtao Cui
- Department of Chemistry, University of Georgia, Athens, GA 30602, USA
| | - Zheng-Hua Ye
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
| |
Collapse
|
24
|
In vitro characterization of the antivirulence target of Gram-positive pathogens, peptidoglycan O-acetyltransferase A (OatA). PLoS Pathog 2017; 13:e1006667. [PMID: 29077761 PMCID: PMC5697884 DOI: 10.1371/journal.ppat.1006667] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 11/21/2017] [Accepted: 09/25/2017] [Indexed: 12/17/2022] Open
Abstract
The O-acetylation of the essential cell wall polymer peptidoglycan occurs in most Gram-positive bacterial pathogens, including species of Staphylococcus, Streptococcus and Enterococcus. This modification to peptidoglycan protects these pathogens from the lytic action of the lysozymes of innate immunity systems and, as such, is recognized as a virulence factor. The key enzyme involved, peptidoglycan O-acetyltransferase A (OatA) represents a particular challenge to biochemical study since it is a membrane associated protein whose substrate is the insoluble peptidoglycan cell wall polymer. OatA is predicted to be bimodular, being comprised of an N-terminal integral membrane domain linked to a C-terminal extracytoplasmic domain. We present herein the first biochemical and kinetic characterization of the C-terminal catalytic domain of OatA from two important human pathogens, Staphylococcus aureus and Streptococcus pneumoniae. Using both pseudosubstrates and novel biosynthetically-prepared peptidoglycan polymers, we characterized distinct substrate specificities for the two enzymes. In addition, the high resolution crystal structure of the C-terminal domain reveals an SGNH/GDSL-like hydrolase fold with a catalytic triad of amino acids but with a non-canonical oxyanion hole structure. Site-specific replacements confirmed the identity of the catalytic and oxyanion hole residues. A model is presented for the O-acetylation of peptidoglycan whereby the translocation of acetyl groups from a cytoplasmic source across the cytoplasmic membrane is catalyzed by the N-terminal domain of OatA for their transfer to peptidoglycan by its C-terminal domain. This study on the structure-function relationship of OatA provides a molecular and mechanistic understanding of this bacterial resistance mechanism opening the prospect for novel chemotherapeutic exploration to enhance innate immunity protection against Gram-positive pathogens. Multi-drug resistance amongst important human pathogens, such as methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE) and drug-resistant Streptococcus pneumoniae (DRSP), continues to challenge clinicians and threaten the lives of infected patients. Of the several approaches being taken to address this serious issue is the development of antagonists that render the bacterial infection more susceptible to the defensive enzymes and proteins of our innate immunity systems. One such target is the enzyme O-acetyltransferase A (OatA). This extracellular enzyme modifies the essential bacterial cell wall component peptidoglycan and thereby makes it resistant to the lytic action of lysozyme, our first line of defense against invading pathogens. In this study, we present the first biochemical and structural characterization of OatA. Using both the S. aureus and S. pneumoniae enzymes as model systems, we demonstrate that OatA has unique substrate specificities. We also show that the catalytic domain of OatA is a structural homolog of a well-studied superfamily of hydrolases. It uses a catalytic triad of Ser-His-Asp to transfer acetyl groups specifically to the C-6 hydroxyl group of muramoyl residues within peptidoglycan. This information on the structure and function relationship of OatA is important for the future development of effective inhibitors which may serve as antivirulence agents.
Collapse
|
25
|
Bonnet J, Durmort C, Jacq M, Mortier-Barrière I, Campo N, VanNieuwenhze MS, Brun YV, Arthaud C, Gallet B, Moriscot C, Morlot C, Vernet T, Di Guilmi AM. Peptidoglycan O-acetylation is functionally related to cell wall biosynthesis and cell division in Streptococcus pneumoniae. Mol Microbiol 2017; 106:832-846. [PMID: 28960579 DOI: 10.1111/mmi.13849] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 09/11/2017] [Accepted: 09/23/2017] [Indexed: 12/12/2022]
Abstract
The peptidoglycan is a rigid matrix required to resist turgor pressure and to maintain the cellular shape. It is formed by linear glycan chains composed of N-acetylmuramic acid-(β-1,4)-N-acetylglucosamine (MurNAc-GlcNAc) disaccharides associated through cross-linked peptide stems. The peptidoglycan is continually remodelled by synthetic and hydrolytic enzymes and by chemical modifications, including O-acetylation of MurNAc residues that occurs in most Gram-positive and Gram-negative bacteria. This modification is a powerful strategy developed by pathogens to resist to lysozyme degradation and thus to escape from the host innate immune system but little is known about its physiological function. In this study, we have investigated to what extend peptidoglycan O-acetylation is involved in cell wall biosynthesis and cell division of Streptococcus pneumoniae. We show that O-acetylation driven by Adr protects the peptidoglycan of dividing cells from cleavage by the major autolysin LytA and occurs at the septal site. Our results support a function for Adr in the formation of robust and mature MurNAc O-acetylated peptidoglycan and infer its role in the division of the pneumococcus.
Collapse
Affiliation(s)
- Julie Bonnet
- Institut de Biologie Structurale (IBS), University Grenoble Alpes, CEA, CNRS, 38044 Grenoble, France
| | - Claire Durmort
- Institut de Biologie Structurale (IBS), University Grenoble Alpes, CEA, CNRS, 38044 Grenoble, France
| | - Maxime Jacq
- Institut de Biologie Structurale (IBS), University Grenoble Alpes, CEA, CNRS, 38044 Grenoble, France
| | - Isabelle Mortier-Barrière
- Laboratoire de Microbiologie et Génétique Moléculaires, Centre de Biologie intégrative (CBI). Centre National de la Recherche Scientifique (CNRS), Université de Toulouse, UPS, F-31000 UMR Toulouse, France
| | - Nathalie Campo
- Laboratoire de Microbiologie et Génétique Moléculaires, Centre de Biologie intégrative (CBI). Centre National de la Recherche Scientifique (CNRS), Université de Toulouse, UPS, F-31000 UMR Toulouse, France
| | | | - Yves V Brun
- Departments of Biology, Indiana University, Bloomington, IN, USA
| | - Christopher Arthaud
- Institut de Biologie Structurale (IBS), University Grenoble Alpes, CEA, CNRS, 38044 Grenoble, France
| | - Benoit Gallet
- Institut de Biologie Structurale (IBS), University Grenoble Alpes, CEA, CNRS, 38044 Grenoble, France
| | - Christine Moriscot
- Institut de Biologie Structurale (IBS), University Grenoble Alpes, CEA, CNRS, 38044 Grenoble, France
| | - Cécile Morlot
- Institut de Biologie Structurale (IBS), University Grenoble Alpes, CEA, CNRS, 38044 Grenoble, France
| | - Thierry Vernet
- Institut de Biologie Structurale (IBS), University Grenoble Alpes, CEA, CNRS, 38044 Grenoble, France
| | - Anne Marie Di Guilmi
- Institut de Biologie Structurale (IBS), University Grenoble Alpes, CEA, CNRS, 38044 Grenoble, France
| |
Collapse
|
26
|
The Pneumococcal Serotype 15C Capsule Is Partially O-Acetylated and Allows for Limited Evasion of 23-Valent Pneumococcal Polysaccharide Vaccine-Elicited Anti-Serotype 15B Antibodies. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2017. [PMID: 28637806 DOI: 10.1128/cvi.00099-17] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
As a species, Streptococcus pneumoniae (the pneumococcus) utilizes a diverse array of capsular polysaccharides to evade the host. In contrast to large variations in sugar composition and linkage formation, O-acetylation is a subtle capsular modification that nonetheless has a large impact on capsular shielding and recognition of the capsule by vaccine-elicited antibodies. Serotype 15B, which is included in the 23-valent pneumococcal polysaccharide vaccine (PPV23), carries the putative O-acetyltransferase gene wciZ The coding sequence of wciZ contains eight consecutive TA repeats [(TA)8]. Replication slippage is thought to result in the addition or loss of TA repeats, subsequently causing frameshift and truncation of WciZ to yield a nonacetylated serotype, 15C. Using sensitive serological tools, we show that serotype 15C isolates whose wciZ contains seven or nine TA repeats retain partial O-acetylation, while serotype 15C isolates whose wciZ contains six TA repeats have barely detectable O-acetylation. We confirmed by inhibition enzyme-linked immunosorbent assay that (TA)7 serotype 15C is ∼0.1% as acetylated as serotype 15B, while serotype 15X is nonacetylated. To eliminate the impact of genetic background, we created isogenic serotype 15B, (TA)7 serotype 15C, and 15BΔwciZ (15X) strains and found that reduction or absence of WciZ-mediated O-acetylation did not affect capsular shielding from phagocytes, biofilm formation, adhesion to nasopharyngeal cells, desiccation tolerance, or murine colonization. Sera from PPV23-immunized persons opsonized serotype 15B significantly but only slightly better than serotypes 15C and 15X; thus, PPV23 may not result in expansion of serotype 15C.
Collapse
|
27
|
Position of O-Acetylation within the Capsular Repeat Unit Impacts the Biological Properties of Pneumococcal Serotypes 33A and 33F. Infect Immun 2017; 85:IAI.00132-17. [PMID: 28438972 DOI: 10.1128/iai.00132-17] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 04/13/2017] [Indexed: 12/26/2022] Open
Abstract
Streptococcus pneumoniae (pneumococcus) produces many capsule types that differ in their abilities to evade host immune recognition. To explain these serotype-dependent protective capacities, many studies have investigated capsular thickness or the interaction of the capsule with complement proteins, but the effects of small chemical modifications of the capsule on its function have not been studied. One small chemical modification found frequently among pneumococcal capsules is O-acetylation. Pneumococcal serotype 33A has two membrane-bound O-acetyltransferase genes, wciG and wcjE A 33A wcjE-deficient variant, 33F, occurs naturally and is increasing in prevalence in the wake of widespread conjugate vaccine use, but no wciG-deficient variants have been reported. To study the biological consequence of the loss of O-acetylation, we created wciG-deficient variants in both serotypes 33A and 33F, which we named 33X1 (ΔwciG) and 33X2 (ΔwciG ΔwcjE). Serotypes 33X1 and 33X2 express novel capsule types based on serological and biochemical analyses. We found that loss of WcjE-mediated O-acetylation appears not to affect cell wall shielding, since serotypes 33A and 33F exhibit comparable nonspecific opsonophagocytic killing, biofilm production, and adhesion to nasopharyngeal cells, though serotype 33F survived short-term drying better than serotype 33A. Loss of WciG-mediated O-acetylation in serotypes 33X1 and 33X2, however, resulted in a phenotype resembling that of nonencapsulated strains: increased cell wall accessibility, increased nonspecific opsonophagocytic killing, enhanced biofilm formation, and increased adhesion to nasopharyngeal cells. We conclude that WciG-mediated, but not WcjE-mediated, O-acetylation is important for producing protective capsules in 33A and that small chemical changes to the capsule can drastically affect its biological properties.
Collapse
|
28
|
Slámová K, Bojarová P. Engineered N-acetylhexosamine-active enzymes in glycoscience. Biochim Biophys Acta Gen Subj 2017; 1861:2070-2087. [PMID: 28347843 DOI: 10.1016/j.bbagen.2017.03.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 03/21/2017] [Accepted: 03/23/2017] [Indexed: 01/17/2023]
Abstract
BACKGROUND In recent years, enzymes modifying N-acetylhexosamine substrates have emerged in numerous theoretical studies as well as practical applications from biology, biomedicine, and biotechnology. Advanced enzyme engineering techniques converted them into potent synthetic instruments affording a variety of valuable glycosides. SCOPE OF REVIEW This review presents the diversity of engineered enzymes active with N-acetylhexosamine carbohydrates: from popular glycoside hydrolases and glycosyltransferases to less known oxidases, epimerases, kinases, sulfotransferases, and acetylases. Though hydrolases in natura, engineered chitinases, β-N-acetylhexosaminidases, and endo-β-N-acetylglucosaminidases were successfully employed in the synthesis of defined natural and derivatized chitooligomers and in the remodeling of N-glycosylation patterns of therapeutic antibodies. The genes of various N-acetylhexosaminyltransferases were cloned into metabolically engineered microorganisms for producing human milk oligosaccharides, Lewis X structures, and human-like glycoproteins. Moreover, mutant N-acetylhexosamine-active glycosyltransferases were applied, e.g., in the construction of glycomimetics and complex glycostructures, industrial production of low-lactose milk, and metabolic labeling of glycans. In the synthesis of biotechnologically important compounds, several innovative glycoengineered systems are presented for an efficient bioproduction of GlcNAc, UDP-GlcNAc, N-acetylneuraminic acid, and of defined glycosaminoglycans. MAJOR CONCLUSIONS The above examples demonstrate that engineering of N-acetylhexosamine-active enzymes was able to solve complex issues such as synthesis of tailored human-like glycoproteins or industrial-scale production of desired oligosaccharides. Due to the specific catalytic mechanism, mutagenesis of these catalysts was often realized through rational solutions. GENERAL SIGNIFICANCE Specific N-acetylhexosamine glycosylation is crucial in biological, biomedical and biotechnological applications and a good understanding of its details opens new possibilities in this fast developing area of glycoscience.
Collapse
Affiliation(s)
- Kristýna Slámová
- Laboratory of Biotransformation, Institute of Microbiology, Czech Academy of Sciences, Vídeňská 1083, CZ 14220 Prague 4, Czech Republic
| | - Pavla Bojarová
- Laboratory of Biotransformation, Institute of Microbiology, Czech Academy of Sciences, Vídeňská 1083, CZ 14220 Prague 4, Czech Republic.
| |
Collapse
|
29
|
Discovery of Novel Pneumococcal Serotype 35D, a Natural WciG-Deficient Variant of Serotype 35B. J Clin Microbiol 2017; 55:1416-1425. [PMID: 28202800 PMCID: PMC5405259 DOI: 10.1128/jcm.00054-17] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 02/09/2017] [Indexed: 11/20/2022] Open
Abstract
Pneumococcus (Streptococcus pneumoniae) remains a significant cause of morbidity and mortality, especially among those at the extremes of age. Its capsular polysaccharide is essential for systemic virulence. Over 90 serologically distinct pneumococcal capsular polysaccharides (serotypes) are recognized, but they are unequal in prevalence. Because antibodies against the capsule are protective, polysaccharide conjugate vaccines, which are constructed against the most prevalent serotypes, have caused great reductions in pneumococcal disease caused by these serotypes. In response, however, the relative prevalences of serotypes have shifted. Certain previously rare serotypes, such as serotype 35B, are increasing in prevalence. Serotype 35B is thus a likely future vaccine candidate, but due to their previous rarity, serotype 35B strains have not been scrutinized for underlying heterogeneity. We studied putative serotype 35B clinical isolates to assess the uniformity of their serological reactions. While most isolates exhibited the accepted serology of serotype 35B, one isolate failed to bind to critical serotyping reagents. We determined that the genetic basis for this aberrant serology was the presence of inactivating mutations in the O-acetyltransferase gene wciG Complementation studies in a wciG deletion strain verified that the mutant WciG was nonfunctional, and the serology of the mutant could be restored through complementation with a construct encoding a functional WciG. Nuclear magnetic resonance studies confirmed that the capsule of the WciG-deficient isolate lacked O-acetylation but was otherwise identical to serotype 35B. As this isolate expresses a unique serology with unique biochemistry and a stable genetic basis, we named its novel capsule serotype 35D.
Collapse
|
30
|
Edgar RJ, Chen J, Kant S, Rechkina E, Rush JS, Forsberg LS, Jaehrig B, Azadi P, Tchesnokova V, Sokurenko EV, Zhu H, Korotkov KV, Pancholi V, Korotkova N. SpyB, a Small Heme-Binding Protein, Affects the Composition of the Cell Wall in Streptococcus pyogenes. Front Cell Infect Microbiol 2016; 6:126. [PMID: 27790410 PMCID: PMC5061733 DOI: 10.3389/fcimb.2016.00126] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 09/27/2016] [Indexed: 12/01/2022] Open
Abstract
Streptococcus pyogenes (Group A Streptococcus or GAS) is a hemolytic human pathogen associated with a wide variety of infections ranging from minor skin and throat infections to life-threatening invasive diseases. The cell wall of GAS consists of peptidoglycan sacculus decorated with a carbohydrate comprising a polyrhamnose backbone with immunodominant N-acetylglucosamine side-chains. All GAS genomes contain the spyBA operon, which encodes a 35-amino-acid membrane protein SpyB, and a membrane-bound C3-like ADP-ribosyltransferase SpyA. In this study, we addressed the function of SpyB in GAS. Phenotypic analysis of a spyB deletion mutant revealed increased bacterial aggregation, and reduced sensitivity to β-lactams of the cephalosporin class and peptidoglycan hydrolase PlyC. Glycosyl composition analysis of cell wall isolated from the spyB mutant suggested an altered carbohydrate structure compared with the wild-type strain. Furthermore, we found that SpyB associates with heme and protoporphyrin IX. Heme binding induces SpyB dimerization, which involves disulfide bond formation between the subunits. Thus, our data suggest the possibility that SpyB activity is regulated by heme.
Collapse
Affiliation(s)
- Rebecca J. Edgar
- Department of Molecular and Cellular Biochemistry, University of KentuckyLexington, KY, USA
| | - Jing Chen
- Department of Molecular and Cellular Biochemistry, University of KentuckyLexington, KY, USA
| | - Sashi Kant
- Department of Pathology, Ohio State UniversityColumbus, OH, USA
| | - Elena Rechkina
- Department of Microbiology, University of WashingtonSeattle, WA, USA
| | - Jeffrey S. Rush
- Department of Molecular and Cellular Biochemistry, University of KentuckyLexington, KY, USA
| | | | - Bernhard Jaehrig
- Complex Carbohydrate Research Center, University of GeorgiaAthens, GA, USA
| | - Parastoo Azadi
- Complex Carbohydrate Research Center, University of GeorgiaAthens, GA, USA
| | | | | | - Haining Zhu
- Department of Molecular and Cellular Biochemistry, University of KentuckyLexington, KY, USA
| | - Konstantin V. Korotkov
- Department of Molecular and Cellular Biochemistry, University of KentuckyLexington, KY, USA
| | - Vijay Pancholi
- Department of Pathology, Ohio State UniversityColumbus, OH, USA
| | - Natalia Korotkova
- Department of Molecular and Cellular Biochemistry, University of KentuckyLexington, KY, USA
| |
Collapse
|
31
|
Kim L, McGee L, Tomczyk S, Beall B. Biological and Epidemiological Features of Antibiotic-Resistant Streptococcus pneumoniae in Pre- and Post-Conjugate Vaccine Eras: a United States Perspective. Clin Microbiol Rev 2016; 29:525-52. [PMID: 27076637 PMCID: PMC4861989 DOI: 10.1128/cmr.00058-15] [Citation(s) in RCA: 169] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Streptococcus pneumoniae inflicts a huge disease burden as the leading cause of community-acquired pneumonia and meningitis. Soon after mainstream antibiotic usage, multiresistant pneumococcal clones emerged and disseminated worldwide. Resistant clones are generated through adaptation to antibiotic pressures imposed while naturally residing within the human upper respiratory tract. Here, a huge array of related commensal streptococcal strains transfers core genomic and accessory resistance determinants to the highly transformable pneumococcus. β-Lactam resistance is the hallmark of pneumococcal adaptability, requiring multiple independent recombination events that are traceable to nonpneumococcal origins and stably perpetuated in multiresistant clonal complexes. Pneumococcal strains with elevated MICs of β-lactams are most often resistant to additional antibiotics. Basic underlying mechanisms of most pneumococcal resistances have been identified, although new insights that increase our understanding are continually provided. Although all pneumococcal infections can be successfully treated with antibiotics, the available choices are limited for some strains. Invasive pneumococcal disease data compiled during 1998 to 2013 through the population-based Active Bacterial Core surveillance program (U.S. population base of 30,600,000) demonstrate that targeting prevalent capsular serotypes with conjugate vaccines (7-valent and 13-valent vaccines implemented in 2000 and 2010, respectively) is extremely effective in reducing resistant infections. Nonetheless, resistant non-vaccine-serotype clones continue to emerge and expand.
Collapse
Affiliation(s)
- Lindsay Kim
- Epidemiology Section, Respiratory Diseases Branch, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Lesley McGee
- Streptococcus Laboratory, Respiratory Diseases Branch, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Sara Tomczyk
- Epidemiology Section, Respiratory Diseases Branch, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Bernard Beall
- Streptococcus Laboratory, Respiratory Diseases Branch, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| |
Collapse
|
32
|
Substrate recognition and catalysis by LytB, a pneumococcal peptidoglycan hydrolase involved in virulence. Sci Rep 2015; 5:16198. [PMID: 26537571 PMCID: PMC4633669 DOI: 10.1038/srep16198] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 10/12/2015] [Indexed: 12/21/2022] Open
Abstract
Streptococcus pneumoniae is a major cause of life-threatening diseases worldwide. Here we provide an in-depth functional characterization of LytB, the peptidoglycan hydrolase responsible for physical separation of daughter cells. Identified herein as an N-acetylglucosaminidase, LytB is involved also in colonization and invasion of the nasopharynx, biofilm formation and evasion of host immunity as previously demonstrated. We have shown that LytB cleaves the GlcNAc-β-(1,4)-MurNAc glycosidic bond of peptidoglycan building units. The hydrolysis occurs at sites with fully acetylated GlcNAc moieties, with preference for uncross-linked muropeptides. The necessity of GlcN acetylation and the presence of a single acidic moiety (Glu585) essential for catalysis strongly suggest a substrate-assisted mechanism with anchimeric assistance of the acetamido group of GlcNAc moieties. Additionally, modelling of the catalytic region bound to a hexasaccharide tripentapeptide provided insights into substrate-binding subsites and peptidoglycan recognition. Besides, cell-wall digestion products and solubilisation rates might indicate a tight control of LytB activity to prevent unrestrained breakdown of the cell wall. Choline-independent localization at the poles of the cell, mediated by the choline-binding domain, peptidoglycan modification, and choline-mediated (lipo)teichoic-acid attachment contribute to the high selectivity of LytB. Moreover, so far unknown chitin hydrolase and glycosyltransferase activities were detected using GlcNAc oligomers as substrate.
Collapse
|
33
|
Minimal Peptidoglycan (PG) Turnover in Wild-Type and PG Hydrolase and Cell Division Mutants of Streptococcus pneumoniae D39 Growing Planktonically and in Host-Relevant Biofilms. J Bacteriol 2015; 197:3472-85. [PMID: 26303829 DOI: 10.1128/jb.00541-15] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 08/15/2015] [Indexed: 12/20/2022] Open
Abstract
UNLABELLED We determined whether there is turnover of the peptidoglycan (PG) cell wall of the ovococcus bacterial pathogen Streptococcus pneumoniae (pneumococcus). Pulse-chase experiments on serotype 2 strain D39 radiolabeled with N-acetylglucosamine revealed little turnover and release of PG breakdown products during growth compared to published reports of PG turnover in Bacillus subtilis. PG dynamics were visualized directly by long-pulse-chase-new-labeling experiments using two colors of fluorescent d-amino acid (FDAA) probes to microscopically detect regions of new PG synthesis. Consistent with minimal PG turnover, hemispherical regions of stable "old" PG persisted in D39 and TIGR4 (serotype 4) cells grown in rich brain heart infusion broth, in D39 cells grown in chemically defined medium containing glucose or galactose as the carbon source, and in D39 cells grown as biofilms on a layer of fixed human epithelial cells. In contrast, B. subtilis exhibited rapid sidewall PG turnover in similar FDAA-labeling experiments. High-performance liquid chromatography (HPLC) analysis of biochemically released peptides from S. pneumoniae PG validated that FDAAs incorporated at low levels into pentamer PG peptides and did not change the overall composition of PG peptides. PG dynamics were also visualized in mutants lacking PG hydrolases that mediate PG remodeling, cell separation, or autolysis and in cells lacking the MapZ and DivIVA division regulators. In all cases, hemispheres of stable old PG were maintained. In PG hydrolase mutants exhibiting aberrant division plane placement, FDAA labeling revealed patches of inert PG at turns and bulge points. We conclude that growing S. pneumoniae cells exhibit minimal PG turnover compared to the PG turnover in rod-shaped cells. IMPORTANCE PG cell walls are unique to eubacteria, and many bacterial species turn over and recycle their PG during growth, stress, colonization, and virulence. Consequently, PG breakdown products serve as signals for bacteria to induce antibiotic resistance and as activators of innate immune responses. S. pneumoniae is a commensal bacterium that colonizes the human nasopharynx and opportunistically causes serious respiratory and invasive diseases. The results presented here demonstrate a distinct demarcation between regions of old PG and regions of new PG synthesis and minimal turnover of PG in S. pneumoniae cells growing in culture or in host-relevant biofilms. These findings suggest that S. pneumoniae minimizes the release of PG breakdown products by turnover, which may contribute to evasion of the innate immune system.
Collapse
|
34
|
Münch D, Sahl HG. Structural variations of the cell wall precursor lipid II in Gram-positive bacteria - Impact on binding and efficacy of antimicrobial peptides. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:3062-71. [PMID: 25934055 DOI: 10.1016/j.bbamem.2015.04.014] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Revised: 04/20/2015] [Accepted: 04/21/2015] [Indexed: 11/25/2022]
Abstract
Antimicrobial peptides (AMPs) are natural antibiotics produced by virtually all living organisms. Typically, AMPs are cationic and amphiphilic and first contacts with target microbes involve interactions with negatively charged components of the cell envelope such as lipopolysaccharide (LPS), and wall- or lipoteichoic acids (WTA, LTA). The importance of charge-mediated interactions of AMPs with the cell envelope is reflected by effective microbial resistance mechanisms which are based on reduction of the overall charge of these polymers. The anionic polymers are linked in various ways to the stress-bearing polymer of the cell envelope, the peptidoglycan, which is made of a highly conserved building block, a disaccharide-pentapeptide moiety that also contains charged residues. This structural element, in spite of its conservation throughout the bacterial world, can undergo genus- and species-specific modifications that also impact significantly on the overall charge of the cell envelope and on the binding affinity of AMPs. The modification reactions involved largely occur on the membrane-bound peptidoglycan building block, the so-called lipid II, which is a most prominent target for AMPs. In this review, we focus on modifications of lipid II and peptidoglycan and discuss their consequences for the interactions with various classes of AMPs, such as defensins, lantibiotics and glyco-(lipo)-peptide antibiotics. This article is part of a Special Issue entitled: Bacterial Resistance to Antimicrobial Peptides.
Collapse
Affiliation(s)
- Daniela Münch
- AiCuris GmbH & Co. KG, Friedrich-Ebert-Str.475, 42117 Wuppertal, Germany
| | - Hans-Georg Sahl
- Institute of Medical Microbiology, Immunology and Parasitology, Pharmaceutical Microbiology Section, University of Bonn, Bonn, Germany.
| |
Collapse
|
35
|
Santiago M, Matano LM, Moussa SH, Gilmore MS, Walker S, Meredith TC. A new platform for ultra-high density Staphylococcus aureus transposon libraries. BMC Genomics 2015; 16:252. [PMID: 25888466 PMCID: PMC4389836 DOI: 10.1186/s12864-015-1361-3] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 02/19/2015] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Staphylococcus aureus readily develops resistance to antibiotics and achieving effective therapies to overcome resistance requires in-depth understanding of S. aureus biology. High throughput, parallel-sequencing methods for analyzing transposon mutant libraries have the potential to revolutionize studies of S. aureus, but the genetic tools to take advantage of the power of next generation sequencing have not been fully developed. RESULTS Here we report a phage-based transposition system to make ultra-high density transposon libraries for genome-wide analysis of mutant fitness in any Φ11-transducible S. aureus strain. The high efficiency of the delivery system has made it possible to multiplex transposon cassettes containing different regulatory elements in order to make libraries in which genes are over- or under-expressed as well as deleted. By incorporating transposon-specific barcodes into the cassettes, we can evaluate how null mutations and changes in gene expression levels affect fitness in a single sequencing data set. Demonstrating the power of the system, we have prepared a library containing more than 690,000 unique insertions. Because one unique feature of the phage-based approach is that temperature-sensitive mutants are retained, we have carried out a genome-wide study of S. aureus genes involved in withstanding temperature stress. We find that many genes previously identified as essential are temperature sensitive and also identify a number of genes that, when disrupted, confer a growth advantage at elevated temperatures. CONCLUSIONS The platform described here reliably provides mutant collections of unparalleled genotypic diversity and will enable a wide range of functional genomic studies in S. aureus.
Collapse
Affiliation(s)
- Marina Santiago
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, 02115, USA.
| | - Leigh M Matano
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, 02115, USA.
| | - Samir H Moussa
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, 02115, USA.
| | - Michael S Gilmore
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, 02115, USA.
- Department of Ophthalmology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, MA, 02114, USA.
| | - Suzanne Walker
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, 02115, USA.
| | - Timothy C Meredith
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, 02115, USA.
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, 16802, USA.
| |
Collapse
|
36
|
LaRock CN, Nizet V. Cationic antimicrobial peptide resistance mechanisms of streptococcal pathogens. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:3047-54. [PMID: 25701232 DOI: 10.1016/j.bbamem.2015.02.010] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Revised: 02/04/2015] [Accepted: 02/07/2015] [Indexed: 02/06/2023]
Abstract
Cationic antimicrobial peptides (CAMPs) are critical front line contributors to host defense against invasive bacterial infection. These immune factors have direct killing activity toward microbes, but many pathogens are able to resist their effects. Group A Streptococcus, group B Streptococcus and Streptococcus pneumoniae are among the most common pathogens of humans and display a variety of phenotypic adaptations to resist CAMPs. Common themes of CAMP resistance mechanisms among the pathogenic streptococci are repulsion, sequestration, export, and destruction. Each pathogen has a different array of CAMP-resistant mechanisms, with invasive disease potential reflecting the utilization of several mechanisms that may act in synergy. Here we discuss recent progress in identifying the sources of CAMP resistance in the medically important Streptococcus genus. Further study of these mechanisms can contribute to our understanding of streptococcal pathogenesis, and may provide new therapeutic targets for therapy and disease prevention. This article is part of a Special Issue entitled: Bacterial Resistance to Antimicrobial Peptides.
Collapse
Affiliation(s)
- Christopher N LaRock
- Department of Pediatrics, University of California, San Diego, La Jolla, CA, USA.
| | - Victor Nizet
- Department of Pediatrics, University of California, San Diego, La Jolla, CA, USA; Skaggs School of Medicine and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA, USA; Rady Children's Hospital, San Diego, CA, USA.
| |
Collapse
|
37
|
Marx P, Meiers M, Brückner R. Activity of the response regulator CiaR in mutants of Streptococcus pneumoniae R6 altered in acetyl phosphate production. Front Microbiol 2015; 5:772. [PMID: 25642214 PMCID: PMC4295557 DOI: 10.3389/fmicb.2014.00772] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Accepted: 12/17/2014] [Indexed: 11/25/2022] Open
Abstract
The two-component regulatory system (TCS) CiaRH of Streptococcus pneumoniae is implicated in competence, ß-lactam resistance, maintenance of cell integrity, bacteriocin production, host colonization, and virulence. Depending on the growth conditions, CiaR can be highly active in the absence of its cognate kinase CiaH, although phosphorylation of CiaR is required for DNA binding and gene regulation. To test the possibility that acetyl phosphate (AcP) could be the alternative phosphodonor, genes involved in pyruvate metabolism were disrupted to alter cellular levels of acetyl phosphate. Inactivating the genes of pyruvate oxidase SpxB, phosphotransacetylase Pta, and acetate kinase AckA, resulted in very low AcP levels and in strongly reduced CiaR-mediated gene expression in CiaH-deficient strains. Therefore, alternative phosphorylation of CiaR appears to proceed via AcP. The AcP effect on CiaR is not detected in strains with CiaH. Attempts to obtain elevated AcP by preventing its degradation by acetate kinase AckA, were not successful in CiaH-deficient strains with a functional SpxB, the most important enzyme for AcP production in S. pneumoniae. The ciaH-spxB-ackA mutant producing intermediate amounts of AcP could be constructed and showed a promoter activation, which was much higher than expected. Since activation was dependent on AcP, it can apparently be used more efficiently for CiaR phosphorylation in the absence of AckA. Therefore, high AcP levels in the absence of CiaH and AckA may cause extreme overexpression of the CiaR regulon leading to synthetic lethality. AckA is also involved in a regulatory response, which is mediated by CiaH. Addition of acetate to the growth medium switch CiaH from kinase to phosphatase. This switch is lost in the absence of AckA indicating metabolism of acetate is required, which starts with the production of AcP by AckA. Therefore, AckA plays a special regulatory role in the control of the CiaRH TCS.
Collapse
Affiliation(s)
- Patrick Marx
- Department of Microbiology, University of Kaiserslautern Kaiserslautern, Germany
| | - Marina Meiers
- Department of Microbiology, University of Kaiserslautern Kaiserslautern, Germany
| | - Reinhold Brückner
- Department of Microbiology, University of Kaiserslautern Kaiserslautern, Germany
| |
Collapse
|
38
|
Abstract
Gram-positive organisms, including the pathogens Staphylococcus aureus, Streptococcus pneumoniae, and Enterococcus faecalis, have dynamic cell envelopes that mediate interactions with the environment and serve as the first line of defense against toxic molecules. Major components of the cell envelope include peptidoglycan (PG), which is a well-established target for antibiotics, teichoic acids (TAs), capsular polysaccharides (CPS), surface proteins, and phospholipids. These components can undergo modification to promote pathogenesis, decrease susceptibility to antibiotics and host immune defenses, and enhance survival in hostile environments. This chapter will cover the structure, biosynthesis, and important functions of major cell envelope components in gram-positive bacteria. Possible targets for new antimicrobials will be noted.
Collapse
|
39
|
Nawrocki KL, Crispell EK, McBride SM. Antimicrobial Peptide Resistance Mechanisms of Gram-Positive Bacteria. Antibiotics (Basel) 2014; 3:461-92. [PMID: 25419466 PMCID: PMC4239024 DOI: 10.3390/antibiotics3040461] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Revised: 09/25/2014] [Accepted: 09/28/2014] [Indexed: 01/09/2023] Open
Abstract
Antimicrobial peptides, or AMPs, play a significant role in many environments as a tool to remove competing organisms. In response, many bacteria have evolved mechanisms to resist these peptides and prevent AMP-mediated killing. The development of AMP resistance mechanisms is driven by direct competition between bacterial species, as well as host and pathogen interactions. Akin to the number of different AMPs found in nature, resistance mechanisms that have evolved are just as varied and may confer broad-range resistance or specific resistance to AMPs. Specific mechanisms of AMP resistance prevent AMP-mediated killing against a single type of AMP, while broad resistance mechanisms often lead to a global change in the bacterial cell surface and protect the bacterium from a large group of AMPs that have similar characteristics. AMP resistance mechanisms can be found in many species of bacteria and can provide a competitive edge against other bacterial species or a host immune response. Gram-positive bacteria are one of the largest AMP producing groups, but characterization of Gram-positive AMP resistance mechanisms lags behind that of Gram-negative species. In this review we present a summary of the AMP resistance mechanisms that have been identified and characterized in Gram-positive bacteria. Understanding the mechanisms of AMP resistance in Gram-positive species can provide guidelines in developing and applying AMPs as therapeutics, and offer insight into the role of resistance in bacterial pathogenesis.
Collapse
Affiliation(s)
- Kathryn L Nawrocki
- Department of Microbiology and Immunology, Emory University School of Medicine, 1510 Clifton Rd, Atlanta, GA 30322, USA; (K.L.N.); (E.K.C.)
| | - Emily K Crispell
- Department of Microbiology and Immunology, Emory University School of Medicine, 1510 Clifton Rd, Atlanta, GA 30322, USA; (K.L.N.); (E.K.C.)
| | - Shonna M McBride
- Department of Microbiology and Immunology, Emory University School of Medicine, 1510 Clifton Rd, Atlanta, GA 30322, USA; (K.L.N.); (E.K.C.)
| |
Collapse
|
40
|
Moynihan PJ, Clarke AJ. Mechanism of action of peptidoglycan O-acetyltransferase B involves a Ser-His-Asp catalytic triad. Biochemistry 2014; 53:6243-51. [PMID: 25215566 DOI: 10.1021/bi501002d] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The O-acetylation of the essential cell wall polymer peptidoglycan is essential in many bacteria for their integrity and survival, and it is catalyzed by peptidoglycan O-acetlytransferase B (PatB). Using PatB from Neisseria gonorrhoeae as the model, we have shown previously that the enzyme has specificity for polymeric muropeptides that possess tri- and tetrapeptide stems and that rates of reaction increase with increasing degrees of polymerization. Here, we present the catalytic mechanism of action of PatB, the first to be described for an O-acetyltransferase of any bacterial exopolysaccharide. The influence of pH on PatB activity was investigated, and pKa values of 6.4-6.45 and 6.25-6.35 for the enzyme-substrate complex (kcat vs pH) and the free enzyme (kcat·KM(-1) vs pH), respectively, were determined for the respective cosubstrates. The enzyme is partially inactivated by sulfonyl fluorides but not by EDTA, suggesting the participation of a serine residue in its catalytic mechanism. Alignment of the known and hypothetical PatB amino acid sequences identified Ser133, Asp302, and His305 as three invariant amino acid residues that could potentially serve as a catalytic triad. Replacement of Asp302 with Ala resulted in an enzyme with less than 20% residual activity, whereas activity was barely detectable with (His305 → Ala)PatB and (Ser133 → Ala)PatB was totally inactive. The reaction intermediate of the transferase reaction involving acetyl- and propionyl-acyl donors was trapped on both the wild-type and (Asp302 → Ala) enzymes and LC-MS/MS analysis of tryptic peptides identified Ser133 as the catalytic nucleophile. A transacetylase mechanism is proposed based on the mechanism of action of serine esterases.
Collapse
Affiliation(s)
- Patrick J Moynihan
- Department of Molecular and Cellular Biology, University of Guelph , Guelph, Ontario N1G 2W1 Canada
| | | |
Collapse
|
41
|
Chewapreecha C, Marttinen P, Croucher NJ, Salter SJ, Harris SR, Mather AE, Hanage WP, Goldblatt D, Nosten FH, Turner C, Turner P, Bentley SD, Parkhill J. Comprehensive identification of single nucleotide polymorphisms associated with beta-lactam resistance within pneumococcal mosaic genes. PLoS Genet 2014; 10:e1004547. [PMID: 25101644 PMCID: PMC4125147 DOI: 10.1371/journal.pgen.1004547] [Citation(s) in RCA: 135] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Accepted: 06/16/2014] [Indexed: 11/18/2022] Open
Abstract
Traditional genetic association studies are very difficult in bacteria, as the generally limited recombination leads to large linked haplotype blocks, confounding the identification of causative variants. Beta-lactam antibiotic resistance in Streptococcus pneumoniae arises readily as the bacteria can quickly incorporate DNA fragments encompassing variants that make the transformed strains resistant. However, the causative mutations themselves are embedded within larger recombined blocks, and previous studies have only analysed a limited number of isolates, leading to the description of “mosaic genes” as being responsible for resistance. By comparing a large number of genomes of beta-lactam susceptible and non-susceptible strains, the high frequency of recombination should break up these haplotype blocks and allow the use of genetic association approaches to identify individual causative variants. Here, we performed a genome-wide association study to identify single nucleotide polymorphisms (SNPs) and indels that could confer beta-lactam non-susceptibility using 3,085 Thai and 616 USA pneumococcal isolates as independent datasets for the variant discovery. The large sample sizes allowed us to narrow the source of beta-lactam non-susceptibility from long recombinant fragments down to much smaller loci comprised of discrete or linked SNPs. While some loci appear to be universal resistance determinants, contributing equally to non-susceptibility for at least two classes of beta-lactam antibiotics, some play a larger role in resistance to particular antibiotics. All of the identified loci have a highly non-uniform distribution in the populations. They are enriched not only in vaccine-targeted, but also non-vaccine-targeted lineages, which may raise clinical concerns. Identification of single nucleotide polymorphisms underlying resistance will be essential for future use of genome sequencing to predict antibiotic sensitivity in clinical microbiology. Streptococcus pneumoniae is carried asymptomatically in the nasopharyngeal tract. However, it is capable of causing multiple diseases, including pneumonia, bacteraemia and meningitis, which are common causes of morbidity and mortality in young children. Antibiotic treatment has become more difficult, especially that involving the group of beta-lactam antibiotics where resistance has developed rapidly. The organism is known to be highly recombinogenic, and this allows variants conferring beta-lactam resistance to be readily introduced into the genome. Identification of the specific genetic determinants of beta-lactam resistance is essential to understand both the mechanism of resistance and the spread of resistant variants in the pneumococcal population. Here, we performed a genome-wide association study on 3,701 isolates collected from two different locations and identified candidate variants that may explain beta-lactam resistance as well as discriminating potential genetic hitchhiking variants from potential causative variants. We report 51 loci, containing 301 SNPs, that are associated with beta-lactam non-susceptibility. 71 out of 301 polymorphic changes result in amino acid alterations, 28 of which have been reported previously. Understanding the determinants of resistance at the single nucleotide level will be important for the future use of sequence data to predict resistance in the clinical setting.
Collapse
Affiliation(s)
- Claire Chewapreecha
- The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Pekka Marttinen
- Center for Communicable Disease Dynamics, Harvard School of Public Health, Boston, Massachusetts, United States of America
- Helsinki Institute for Information Technology HIIT, Department of Information and Computer Science, Aalto University, Espoo, Finland
| | - Nicholas J. Croucher
- Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Susannah J. Salter
- The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Simon R. Harris
- The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Alison E. Mather
- The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - William P. Hanage
- Center for Communicable Disease Dynamics, Harvard School of Public Health, Boston, Massachusetts, United States of America
| | - David Goldblatt
- Immunobiology Unit, Institute of Child Health, University College London, London, United Kingdom
| | - Francois H. Nosten
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Maesot, Thailand
- Centre for Tropical Medicine, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Claudia Turner
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Maesot, Thailand
- Centre for Tropical Medicine, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
- Cambodia-Oxford Medical Research Unit, Angkor Hospital for Children, Siem Reap, Cambodia
| | - Paul Turner
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Maesot, Thailand
- Centre for Tropical Medicine, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
- Cambodia-Oxford Medical Research Unit, Angkor Hospital for Children, Siem Reap, Cambodia
| | - Stephen D. Bentley
- The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom
- * E-mail: (SDB); (JP)
| | - Julian Parkhill
- The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
- * E-mail: (SDB); (JP)
| |
Collapse
|
42
|
Yang S, Zhang F, Kang J, Zhang W, Deng G, Xin Y, Ma Y. Mycobacterium tuberculosis Rv1096 protein: gene cloning, protein expression, and peptidoglycan deacetylase activity. BMC Microbiol 2014; 14:174. [PMID: 24975018 PMCID: PMC4087242 DOI: 10.1186/1471-2180-14-174] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 06/25/2014] [Indexed: 01/26/2023] Open
Abstract
Background Many bacteria modulate and evade the immune defenses of their hosts through peptidoglycan (PG) deacetylation. The PG deacetylases from Streptococcus pneumonia, Listeria monocytogenes and Lactococcus lactis have been characterized. However, thus far, the PG deacetylase of Mycobacterium tuberculosis has not been identified. Results In this study, we cloned the Rv1096 gene from the M. tuberculosis H37Rv strain and expressed Rv1096 protein in both Escherichia coli and M. smegmatis. The results showed that the purified Rv1096 protein possessed metallo-dependent PG deacetylase activity, which increased in the presence of Co2+. The kinetic parameters of the PG deacetylase towards M. smegmatis PG as a substrate were as follows: Km, 0.910 ± 0.007 mM; Vmax, 0.514 ± 0.038 μMmin-1; and Kcat = 0.099 ± 0.007 (S-1). Additionally, the viability of M. smegmatis in the presence of over-expressed Rv1096 protein was 109-fold higher than that of wild-type M. smegmatis after lysozyme treatment. Additionally, light microscopy and scanning electron microscopy showed that in the presence of over-expressed Rv1096 protein, M. smegmatis kept its regular shape, with an undamaged cell wall and smooth surface. These results indicate that Rv1096 caused deacetylation of cell wall PG, leading to lysozyme resistance in M. smegmatis. Conclusion We have determined that M. tuberculosis Rv1096 is a PG deacetylase. The PG deacetylase activity of Rv1096 contributed to lysozyme resistance in M. smegmatis. Our findings suggest that deacetylation of cell wall PG may be involved in evasion of host immune defenses by M. tuberculosis.
Collapse
Affiliation(s)
| | | | | | | | | | | | - Yufang Ma
- Department of Biochemistry and Molecular Biology, Dalian Medical University, 9 W Lushun South Road, Dalian 116044, China.
| |
Collapse
|
43
|
Okumura CYM, Nizet V. Subterfuge and sabotage: evasion of host innate defenses by invasive gram-positive bacterial pathogens. Annu Rev Microbiol 2014; 68:439-58. [PMID: 25002085 DOI: 10.1146/annurev-micro-092412-155711] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The development of a severe invasive bacterial infection in an otherwise healthy individual is one of the most striking and fascinating aspects of human medicine. A small cadre of gram-positive pathogens of the genera Streptococcus and Staphylococcus stand out for their unique invasive disease potential and sophisticated ability to counteract the multifaceted components of human innate defense. This review illustrates how these leading human disease agents evade host complement deposition and activation, impede phagocyte recruitment and activation, resist the microbicidal activities of host antimicrobial peptides and reactive oxygen species, escape neutrophil extracellular traps, and promote and accelerate phagocyte cell death through the action of pore-forming cytolysins. Understanding the molecular basis of bacterial innate immune resistance can open new avenues for therapeutic intervention geared to disabling specific virulence factors and resensitizing the pathogen to host innate immune clearance.
Collapse
Affiliation(s)
- Cheryl Y M Okumura
- Department of Biology, Occidental College, Los Angeles, California 90041;
| | | |
Collapse
|
44
|
Chemical biology of peptidoglycan acetylation and deacetylation. Bioorg Chem 2014; 54:44-50. [DOI: 10.1016/j.bioorg.2014.03.010] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 03/25/2014] [Indexed: 12/16/2022]
|
45
|
Moynihan PJ, Clarke AJ. Substrate specificity and kinetic characterization of peptidoglycan O-acetyltransferase B from Neisseria gonorrhoeae. J Biol Chem 2014; 289:16748-60. [PMID: 24795044 DOI: 10.1074/jbc.m114.567388] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The O-acetylation of the essential cell wall polymer peptidoglycan is a major virulence factor identified in many bacteria, both Gram-positive and Gram-negative, including Staphylococcus aureus, Bacillus anthracis, Neisseria gonorrhoeae, and Neisseria meningitidis. With Gram-negative bacteria, the translocation of acetyl groups from the cytoplasm is performed by an integral membrane protein, PatA, for its transfer to peptidoglycan by O-acetyltransferase PatB, whereas a single bimodal membrane protein, OatA, appears to catalyze both reactions of the process in Gram-positive bacteria. Only phenotypic evidence existed in support of these pathways because no in vitro biochemical assay was available for their analysis, which reflected the complexities of investigating integral membrane proteins that act on a totally insoluble and heterogeneous substrate, such as peptidoglycan. In this study, we present the first biochemical and kinetic analysis of a peptidoglycan O-acetyltransferase using PatB from N. gonorrhoeae as the model system. The enzyme has specificity for muropeptides that possess tri- and tetrapeptide stems on muramyl residues. With chitooligosaccharides as substrates, rates of reaction increase with increasing degrees of polymerization to 5/6. This information will be valuable for the identification and development of peptidoglycan O-acetyltransferase inhibitors that could represent potential leads to novel classes of antibiotics.
Collapse
Affiliation(s)
- Patrick J Moynihan
- From the Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Anthony J Clarke
- From the Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| |
Collapse
|
46
|
Verhagen LM, de Jonge MI, Burghout P, Schraa K, Spagnuolo L, Mennens S, Eleveld MJ, van der Gaast-de Jongh CE, Zomer A, Hermans PWM, Bootsma HJ. Genome-wide identification of genes essential for the survival of Streptococcus pneumoniae in human saliva. PLoS One 2014; 9:e89541. [PMID: 24586856 PMCID: PMC3934895 DOI: 10.1371/journal.pone.0089541] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 01/22/2014] [Indexed: 11/19/2022] Open
Abstract
Since Streptococcus pneumoniae transmits through droplet spread, this respiratory tract pathogen may be able to survive in saliva. Here, we show that saliva supports survival of clinically relevant S. pneumoniae strains for more than 24 h in a capsule-independent manner. Moreover, saliva induced growth of S. pneumoniae in growth-permissive conditions, suggesting that S. pneumoniae is well adapted for uptake of nutrients from this bodily fluid. By using Tn-seq, a method for genome-wide negative selection screening, we identified 147 genes potentially required for growth and survival of S. pneumoniae in saliva, among which genes predicted to be involved in cell envelope biosynthesis, cell transport, amino acid metabolism, and stress response predominated. The Tn-seq findings were validated by testing a panel of directed gene deletion mutants for their ability to survive in saliva under two testing conditions: at room temperature without CO2, representing transmission, and at 37°C with CO2, representing in-host carriage. These validation experiments confirmed that the plsX gene and the amiACDEF and aroDEBC operons, involved in respectively fatty acid metabolism, oligopeptide transport, and biosynthesis of aromatic amino acids play an important role in the growth and survival of S. pneumoniae in saliva at 37°C. In conclusion, this study shows that S. pneumoniae is well-adapted for growth and survival in human saliva and provides a genome-wide list of genes potentially involved in adaptation. This notion supports earlier evidence that S. pneumoniae can use human saliva as a vector for transmission.
Collapse
Affiliation(s)
- Lilly M. Verhagen
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Marien I. de Jonge
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Peter Burghout
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Kiki Schraa
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Lorenza Spagnuolo
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Svenja Mennens
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Marc J. Eleveld
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands
| | | | - Aldert Zomer
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands
- Centre for Molecular and Biomolecular Informatics, Nijmegen Centre for Molecular Life Sciences, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Peter W. M. Hermans
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Hester J. Bootsma
- Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands
- * E-mail:
| |
Collapse
|
47
|
Genomic analyses of DNA transformation and penicillin resistance in Streptococcus pneumoniae clinical isolates. Antimicrob Agents Chemother 2013; 58:1397-403. [PMID: 24342643 DOI: 10.1128/aac.01311-13] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Alterations in penicillin-binding proteins, the target enzymes for β-lactam antibiotics, are recognized as primary penicillin resistance mechanisms in Streptococcus pneumoniae. Few studies have analyzed penicillin resistance at the genome scale, however, and we report the sequencing of S. pneumoniae R6 transformants generated while reconstructing the penicillin resistance phenotypes from three penicillin-resistant clinical isolates by serial genome transformation. The genome sequences of the three last-level transformants T2-18209, T5-1983, and T3-55938 revealed that 16.2 kb, 82.7 kb, and 137.2 kb of their genomes had been replaced with 5, 20, and 37 recombinant sequence segments derived from their respective parental clinical isolates, documenting the extent of DNA transformation between strains. A role in penicillin resistance was confirmed for some of the mutations identified in the transformants. Several multiple recombination events were also found to have happened at single loci coding for penicillin-binding proteins (PBPs) that increase resistance. Sequencing of the transformants with MICs for penicillin similar to those of the parent clinical strains confirmed the importance of mosaic PBP2x, -2b, and -1a as a driving force in penicillin resistance. A role in resistance for mosaic PBP2a was also observed for two of the resistant clinical isolates.
Collapse
|
48
|
Sukhithasri V, Nisha N, Biswas L, Anil Kumar V, Biswas R. Innate immune recognition of microbial cell wall components and microbial strategies to evade such recognitions. Microbiol Res 2013; 168:396-406. [DOI: 10.1016/j.micres.2013.02.005] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2012] [Revised: 02/08/2013] [Accepted: 02/09/2013] [Indexed: 01/19/2023]
|
49
|
Fani F, Brotherton MC, Leprohon P, Ouellette M. Genomic analysis and reconstruction of cefotaxime resistance in Streptococcus pneumoniae. J Antimicrob Chemother 2013; 68:1718-27. [PMID: 23608923 DOI: 10.1093/jac/dkt113] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVES To identify non-penicillin-binding protein (PBP) mutations contributing to resistance to the third-generation cephalosporin cefotaxime in Streptococcus pneumoniae at the genome-wide scale. METHODS The genomes of two in vitro S. pneumoniae cefotaxime-resistant isolates and of two transformants serially transformed with the genomic DNA of cefotaxime-resistant mutants were determined by next-generation sequencing. A role in cefotaxime resistance for the mutations identified was confirmed by reconstructing resistance in a cefotaxime-susceptible background. RESULTS Analysis of the genome assemblies revealed mutations in genes coding for the PBPs 2x, 2a and 3, of which pbp2x was the only mutated gene common to all mutants. The transformation of altered PBP alleles into S. pneumoniae R6 confirmed the role of PBP mutations in cefotaxime resistance, but these were not sufficient to fully explain the levels of resistance. Thirty-one additional genes were found to be mutated in at least one of the four sequenced genomes. Non-PBP resistance determinants appeared to be mostly lineage specific. Mutations in spr1333, spr0981, spr1704 and spr1098, encoding a peptidoglycan N-acetylglucosamine deacetylase, a glycosyltransferase, an ABC transporter and a sortase, respectively, were implicated in resistance by transformation experiments and allowed the reconstruction of the full level of resistance observed in the parent resistant strains. CONCLUSIONS This whole-genome analysis coupled to functional studies has allowed the discovery of both known and novel cefotaxime resistance genes in S. pneumoniae.
Collapse
Affiliation(s)
- Fereshteh Fani
- Centre de recherche en Infectiologie du Centre de recherche du CHUL and Département de Microbiologie, Infectiologie et Immunologie, Faculté de Médecine, Université Laval, Québec, Canada
| | | | | | | |
Collapse
|
50
|
Bernard E, Rolain T, David B, André G, Dupres V, Dufrêne YF, Hallet B, Chapot-Chartier MP, Hols P. Dual role for the O-acetyltransferase OatA in peptidoglycan modification and control of cell septation in Lactobacillus plantarum. PLoS One 2012; 7:e47893. [PMID: 23110121 PMCID: PMC3482227 DOI: 10.1371/journal.pone.0047893] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 09/17/2012] [Indexed: 11/30/2022] Open
Abstract
Until now, peptidoglycan O-acetyl transferases (Oat) were only described for their peptidoglycan O-acetylating activity and for their implication in the control of peptidoglycan hydrolases. In this study, we show that a Lactobacillus plantarum mutant lacking OatA is unable to uncouple cell elongation and septation. Wild-type cells showed an elongation arrest during septation while oatA mutant cells continued to elongate at a constant rate without any observable pause during the cell division process. Remarkably, this defect does not result from a default in peptidoglycan O-acetylation, since it can be rescued by wild-type OatA as well as by a catalytic mutant or a truncated variant containing only the transmembrane domain of the protein. Consistent with a potential involvement in division, OatA preferentially localizes at mid-cell before membrane invagination and remains at this position until the end of septation. Overexpression of oatA or its inactive variants induces septation-specific aberrations, including asymmetrical and dual septum formation. Overproduction of the division inhibitors, MinC or MinD, leads to cell filamentation in the wild type while curved and branched cells are observed in the oatA mutant, suggesting that the Min system acts differently on the division process in the absence of OatA. Altogether, the results suggest that OatA plays a key role in the spatio-temporal control of septation, irrespective of its catalytic activity.
Collapse
Affiliation(s)
- Elvis Bernard
- Institut National de la Recherche Agronomique, UMR1319 Micalis, Jouy-en-Josas, France
- AgroParisTech, UMR Micalis, Jouy-en-Josas, France
- Biochimie et Génétique Moléculaire Bactérienne, Institut des Sciences de la Vie, Université catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Thomas Rolain
- Biochimie et Génétique Moléculaire Bactérienne, Institut des Sciences de la Vie, Université catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Blandine David
- Biochimie et Génétique Moléculaire Bactérienne, Institut des Sciences de la Vie, Université catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Guillaume André
- Bio and Soft Matter, Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Vincent Dupres
- Bio and Soft Matter, Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Yves F. Dufrêne
- Bio and Soft Matter, Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Bernard Hallet
- Biochimie et Génétique Moléculaire Bactérienne, Institut des Sciences de la Vie, Université catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Marie-Pierre Chapot-Chartier
- Institut National de la Recherche Agronomique, UMR1319 Micalis, Jouy-en-Josas, France
- AgroParisTech, UMR Micalis, Jouy-en-Josas, France
| | - Pascal Hols
- Biochimie et Génétique Moléculaire Bactérienne, Institut des Sciences de la Vie, Université catholique de Louvain, Louvain-la-Neuve, Belgium
- * E-mail:
| |
Collapse
|