1
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Garrett SR, Palmer T. The role of proteinaceous toxins secreted by Staphylococcus aureus in interbacterial competition. FEMS MICROBES 2024; 5:xtae006. [PMID: 38495077 PMCID: PMC10941976 DOI: 10.1093/femsmc/xtae006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2023] [Revised: 02/17/2024] [Accepted: 02/27/2024] [Indexed: 03/19/2024] Open
Abstract
Staphylococcus aureus is highly adapted to colonization of the mammalian host. In humans the primary site of colonization is the epithelium of the nasal cavity. A major barrier to colonization is the resident microbiota, which have mechanisms to exclude S. aureus. As such, S. aureus has evolved mechanisms to compete with other bacteria, one of which is through secretion of proteinaceous toxins. S. aureus strains collectively produce a number of well-characterized Class I, II, and IV bacteriocins as well as several bacteriocin-like substances, about which less is known. These bacteriocins have potent antibacterial activity against several Gram-positive organisms, with some also active against Gram-negative species. S. aureus bacteriocins characterized to date are sporadically produced, and often encoded on plasmids. More recently the type VII secretion system (T7SS) of S. aureus has also been shown to play a role in interbacterial competition. The T7SS is encoded by all S. aureus isolates and so may represent a more widespread mechanism of competition used by this species. T7SS antagonism is mediated by the secretion of large protein toxins, three of which have been characterized to date: a nuclease toxin, EsaD; a membrane depolarizing toxin, TspA; and a phospholipase toxin, TslA. Further study is required to decipher the role that these different types of secreted toxins play in interbacterial competition and colonization of the host.
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Affiliation(s)
- Stephen R Garrett
- Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, United Kingdom
| | - Tracy Palmer
- Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, United Kingdom
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2
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Wang S, Mu L, Yu C, He Y, Hu X, Jiao Y, Xu Z, You S, Liu SL, Bao H. Microbial collaborations and conflicts: unraveling interactions in the gut ecosystem. Gut Microbes 2024; 16:2296603. [PMID: 38149632 PMCID: PMC10761165 DOI: 10.1080/19490976.2023.2296603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 12/14/2023] [Indexed: 12/28/2023] Open
Abstract
The human gut microbiota constitutes a vast and complex community of microorganisms. The myriad of microorganisms present in the intestinal tract exhibits highly intricate interactions, which play a crucial role in maintaining the stability and balance of the gut microbial ecosystem. These interactions, in turn, influence the overall health of the host. The mammalian gut microbes have evolved a wide range of mechanisms to suppress or even eliminate their competitors for nutrients and space. Simultaneously, extensive cooperative interactions exist among different microbes to optimize resource utilization and enhance their own fitness. This review will focus on the competitive mechanisms among members of the gut microorganisms and discuss key modes of actions, including bacterial secretion systems, bacteriocins, membrane vesicles (MVs) etc. Additionally, we will summarize the current knowledge of the often-overlooked positive interactions within the gut microbiota, and showcase representative machineries. This information will serve as a reference for better understanding the complex interactions occurring within the mammalian gut environment. Understanding the interaction dynamics of competition and cooperation within the gut microbiota is crucial to unraveling the ecology of the mammalian gut microbial communities. Targeted interventions aimed at modulating these interactions may offer potential therapeutic strategies for disease conditions.
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Affiliation(s)
- Shuang Wang
- Genomics Research Center, Key Laboratory of Gut Microbiota and Pharmacogenomics of Heilongjiang Province, State-Province Key Laboratory of Biomedicine-Pharmaceutics of China, College of Pharmacy, Harbin Medical University, Harbin, China
- Department of Biopharmaceutical Sciences (State-Province Key Laboratories of Biomedicine-Pharmaceutics of China), College of Pharmacy, Harbin Medical University, Harbin, China
- National Key Laboratory of Frigid Zone Cardiovascular Diseases (NKLFZCD) College of Pharmacy, Harbin Medical University, Harbin, China
| | - Lingyi Mu
- Genomics Research Center, Key Laboratory of Gut Microbiota and Pharmacogenomics of Heilongjiang Province, State-Province Key Laboratory of Biomedicine-Pharmaceutics of China, College of Pharmacy, Harbin Medical University, Harbin, China
| | - Chong Yu
- Genomics Research Center, Key Laboratory of Gut Microbiota and Pharmacogenomics of Heilongjiang Province, State-Province Key Laboratory of Biomedicine-Pharmaceutics of China, College of Pharmacy, Harbin Medical University, Harbin, China
- National Key Laboratory of Frigid Zone Cardiovascular Diseases (NKLFZCD) College of Pharmacy, Harbin Medical University, Harbin, China
- Harbin Medical University-University of Calgary Cumming School of Medicine Centre for Infection and Genomics, Harbin Medical University, Harbin, China
| | - Yuting He
- Genomics Research Center, Key Laboratory of Gut Microbiota and Pharmacogenomics of Heilongjiang Province, State-Province Key Laboratory of Biomedicine-Pharmaceutics of China, College of Pharmacy, Harbin Medical University, Harbin, China
- National Key Laboratory of Frigid Zone Cardiovascular Diseases (NKLFZCD) College of Pharmacy, Harbin Medical University, Harbin, China
- Harbin Medical University-University of Calgary Cumming School of Medicine Centre for Infection and Genomics, Harbin Medical University, Harbin, China
| | - Xinliang Hu
- Genomics Research Center, Key Laboratory of Gut Microbiota and Pharmacogenomics of Heilongjiang Province, State-Province Key Laboratory of Biomedicine-Pharmaceutics of China, College of Pharmacy, Harbin Medical University, Harbin, China
- National Key Laboratory of Frigid Zone Cardiovascular Diseases (NKLFZCD) College of Pharmacy, Harbin Medical University, Harbin, China
- Harbin Medical University-University of Calgary Cumming School of Medicine Centre for Infection and Genomics, Harbin Medical University, Harbin, China
| | - Yanlei Jiao
- Genomics Research Center, Key Laboratory of Gut Microbiota and Pharmacogenomics of Heilongjiang Province, State-Province Key Laboratory of Biomedicine-Pharmaceutics of China, College of Pharmacy, Harbin Medical University, Harbin, China
- National Key Laboratory of Frigid Zone Cardiovascular Diseases (NKLFZCD) College of Pharmacy, Harbin Medical University, Harbin, China
- Harbin Medical University-University of Calgary Cumming School of Medicine Centre for Infection and Genomics, Harbin Medical University, Harbin, China
| | - Ziqiong Xu
- Genomics Research Center, Key Laboratory of Gut Microbiota and Pharmacogenomics of Heilongjiang Province, State-Province Key Laboratory of Biomedicine-Pharmaceutics of China, College of Pharmacy, Harbin Medical University, Harbin, China
- National Key Laboratory of Frigid Zone Cardiovascular Diseases (NKLFZCD) College of Pharmacy, Harbin Medical University, Harbin, China
- Harbin Medical University-University of Calgary Cumming School of Medicine Centre for Infection and Genomics, Harbin Medical University, Harbin, China
| | - Shaohui You
- Genomics Research Center, Key Laboratory of Gut Microbiota and Pharmacogenomics of Heilongjiang Province, State-Province Key Laboratory of Biomedicine-Pharmaceutics of China, College of Pharmacy, Harbin Medical University, Harbin, China
- National Key Laboratory of Frigid Zone Cardiovascular Diseases (NKLFZCD) College of Pharmacy, Harbin Medical University, Harbin, China
- Harbin Medical University-University of Calgary Cumming School of Medicine Centre for Infection and Genomics, Harbin Medical University, Harbin, China
| | - Shu-Lin Liu
- Genomics Research Center, Key Laboratory of Gut Microbiota and Pharmacogenomics of Heilongjiang Province, State-Province Key Laboratory of Biomedicine-Pharmaceutics of China, College of Pharmacy, Harbin Medical University, Harbin, China
- National Key Laboratory of Frigid Zone Cardiovascular Diseases (NKLFZCD) College of Pharmacy, Harbin Medical University, Harbin, China
- Harbin Medical University-University of Calgary Cumming School of Medicine Centre for Infection and Genomics, Harbin Medical University, Harbin, China
| | - Hongxia Bao
- Genomics Research Center, Key Laboratory of Gut Microbiota and Pharmacogenomics of Heilongjiang Province, State-Province Key Laboratory of Biomedicine-Pharmaceutics of China, College of Pharmacy, Harbin Medical University, Harbin, China
- National Key Laboratory of Frigid Zone Cardiovascular Diseases (NKLFZCD) College of Pharmacy, Harbin Medical University, Harbin, China
- Harbin Medical University-University of Calgary Cumming School of Medicine Centre for Infection and Genomics, Harbin Medical University, Harbin, China
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3
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Sannino DR, Arroyo FA, Pepe-Ranney C, Chen W, Volland JM, Elisabeth NH, Angert ER. The exceptional form and function of the giant bacterium Ca. Epulopiscium viviparus revolves around its sodium motive force. Proc Natl Acad Sci U S A 2023; 120:e2306160120. [PMID: 38109545 PMCID: PMC10756260 DOI: 10.1073/pnas.2306160120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2023] [Accepted: 11/09/2023] [Indexed: 12/20/2023] Open
Abstract
Epulopiscium spp. are the largest known heterotrophic bacteria; a large cigar-shaped individual is a million times the volume of Escherichia coli. To better understand the metabolic potential and relationship of Epulopiscium sp. type B with its host Naso tonganus, we generated a high-quality draft genome from a population of cells taken from a single fish. We propose the name Candidatus Epulopiscium viviparus to describe populations of this best-characterized Epulopiscium species. Metabolic reconstruction reveals more than 5% of the genome codes for carbohydrate active enzymes, which likely degrade recalcitrant host-diet algal polysaccharides into substrates that may be fermented to acetate, the most abundant short-chain fatty acid in the intestinal tract. Moreover, transcriptome analyses and the concentration of sodium ions in the host intestinal tract suggest that the use of a sodium motive force (SMF) to drive ATP synthesis and flagellar rotation is integral to symbiont metabolism and cellular biology. In natural populations, genes encoding both F-type and V-type ATPases and SMF generation via oxaloacetate decarboxylation are among the most highly expressed, suggesting that ATPases synthesize ATP and balance ion concentrations across the cell membrane. High expression of these and other integral membrane proteins may allow for the growth of its extensive intracellular membrane system. Further, complementary metabolism between microbe and host is implied with the potential provision of nitrogen and B vitamins to reinforce this nutritional symbiosis. The few features shared by all bacterial behemoths include extreme polyploidy, polyphosphate synthesis, and thus far, they have all resisted cultivation in the lab.
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Affiliation(s)
| | | | - Charles Pepe-Ranney
- Soil & Crop Sciences Section, School of Integrative Plant Sciences, Cornell University, Ithaca, NY14853
| | - Wenbo Chen
- Department of Microbiology, Cornell University, Ithaca, NY14853
| | - Jean-Marie Volland
- Laboratory for Research in Complex Systems, Menlo Park, CA94025
- Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA94720
| | - Nathalie H. Elisabeth
- Department of Energy Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA94720
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4
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Teh WK, Ding Y, Gubellini F, Filloux A, Poyart C, Givskov M, Dramsi S. Characterization of TelE, a T7SS LXG Effector Exhibiting a Conserved C-Terminal Glycine Zipper Motif Required for Toxicity. Microbiol Spectr 2023; 11:e0148123. [PMID: 37432124 PMCID: PMC10434224 DOI: 10.1128/spectrum.01481-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 06/22/2023] [Indexed: 07/12/2023] Open
Abstract
Streptococcus gallolyticus subsp. gallolyticus (SGG) is an opportunistic bacterial pathogen strongly associated with colorectal cancer. Here, through comparative genomics analysis, we demonstrated that the genetic locus encoding the type VIIb secretion system (T7SSb) machinery is uniquely present in SGG in two different arrangements. SGG UCN34 carrying the most prevalent T7SSb genetic arrangement was chosen as the reference strain. To identify the effectors secreted by this secretion system, we inactivated the essC gene encoding the motor of this machinery. A comparison of the proteins secreted by UCN34 wild type and its isogenic ΔessC mutant revealed six T7SSb effector proteins, including the expected WXG effector EsxA and three LXG-containing proteins. In this work, we characterized an LXG-family toxin named herein TelE promoting the loss of membrane integrity. Seven homologs of TelE harboring a conserved glycine zipper motif at the C terminus were identified in different SGG isolates. Scanning mutagenesis of this motif showed that the glycine residue at position 470 was crucial for TelE membrane destabilization activity. TelE activity was antagonized by a small protein TipE belonging to the DUF5085 family. Overall, we report herein a unique SGG T7SSb effector exhibiting a toxic activity against nonimmune bacteria. IMPORTANCE In this study, 38 clinical isolates of Streptococcus gallolyticus subsp. gallolyticus (SGG) were sequenced and a genetic locus encoding the type VIIb secretion system (T7SSb) was found conserved and absent from 16 genomes of the closely related S. gallolyticus subsp. pasteurianus (SGP). The T7SSb is a bona fide pathogenicity island. Here, we report that the model organism SGG strain UCN34 secretes six T7SSb effectors. One of the six effectors named TelE displayed a strong toxicity when overexpressed in Escherichia coli. Our results indicate that TelE is probably a pore-forming toxin whose activity can be antagonized by a specific immunity protein named TipE. Overall, we report a unique toxin-immunity protein pair and our data expand the range of effectors secreted through T7SSb.
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Affiliation(s)
- Wooi Keong Teh
- Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
| | - Yichen Ding
- Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
| | | | - Alain Filloux
- Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
- Centre for Bacterial Resistance Biology, Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Claire Poyart
- Université de Paris, Assistance Publique Hôpitaux de Paris, Service de Bactériologie, Centre National de Référence des Streptocoques, Groupe Hospitalier Paris Centre site Cochin, Paris, France
| | - Michael Givskov
- Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
- Costerton Biofilm Centre, Department of Immunology and Microbiology, University of Copenhagen, Denmark
| | - Shaynoor Dramsi
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Biology of Gram-positive Pathogens Unit, Paris, France
- Centre National de la Recherche Scientifique (CNRS) UMR2001, Paris, France
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5
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Spencer BL, Job AM, Robertson CM, Hameed ZA, Serchejian C, Wiafe-Kwakye CS, Mendonça JC, Apolonio MA, Nagao PE, Neely MN, Korotkova N, Korotkov KV, Patras KA, Doran KS. Heterogeneity of the group B streptococcal type VII secretion system and influence on colonization of the female genital tract. Mol Microbiol 2023; 120:258-275. [PMID: 37357823 PMCID: PMC10527989 DOI: 10.1111/mmi.15115] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 06/06/2023] [Accepted: 06/08/2023] [Indexed: 06/27/2023]
Abstract
Type VIIb secretion systems (T7SSb) in Gram-positive bacteria facilitate physiology, interbacterial competition, and/or virulence via EssC ATPase-driven secretion of small ɑ-helical proteins and toxins. Recently, we characterized T7SSb in group B Streptococcus (GBS), a leading cause of infection in newborns and immunocompromised adults. GBS T7SS comprises four subtypes based on variation in the C-terminus of EssC and the repertoire of downstream effectors; however, the intraspecies diversity of GBS T7SS and impact on GBS-host interactions remains unknown. Bioinformatic analysis indicates that GBS T7SS loci encode subtype-specific putative effectors, which have low interspecies and inter-subtype homology but contain similar domains/motifs and therefore may serve similar functions. We further identify orphaned GBS WXG100 proteins. Functionally, we show that GBS T7SS subtype I and III strains secrete EsxA in vitro and that in subtype I strain CJB111, esxA1 appears to be differentially transcribed from the T7SS operon. Furthermore, we observe subtype-specific effects of GBS T7SS on host colonization, as CJB111 subtype I but not CNCTC 10/84 subtype III T7SS promotes GBS vaginal colonization. Finally, we observe that T7SS subtypes I and II are the predominant subtypes in clinical GBS isolates. This study highlights the potential impact of T7SS heterogeneity on host-GBS interactions.
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Affiliation(s)
- Brady L. Spencer
- University of Colorado-Anschutz, Department of Immunology and Microbiology, Aurora, CO, USA
| | - Alyx M. Job
- University of Colorado-Anschutz, Department of Immunology and Microbiology, Aurora, CO, USA
| | - Clare M. Robertson
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Zainab A. Hameed
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Camille Serchejian
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | | | - Jéssica C. Mendonça
- University of Colorado-Anschutz, Department of Immunology and Microbiology, Aurora, CO, USA
- Rio de Janeiro State University, Roberto Alcântara Gomes Biology Institute, Rio de Janeiro, RJ, Brazil
| | - Morgan A. Apolonio
- University of Colorado-Anschutz, Department of Immunology and Microbiology, Aurora, CO, USA
- National Summer Undergraduate Research Program, University of Arizona, Tucson, AZ, USA
| | - Prescilla E. Nagao
- Rio de Janeiro State University, Roberto Alcântara Gomes Biology Institute, Rio de Janeiro, RJ, Brazil
| | - Melody N. Neely
- University of Maine, Molecular & Biomedical Sciences, Orono, ME, USA
| | - Natalia Korotkova
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky, Lexington, KY, USA
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, USA
| | - Konstantin V. Korotkov
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, USA
| | - Kathryn A. Patras
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
- Alkek Center for Metagenomics and Microbiome Research, Baylor College of Medicine, Houston, TX, USA
| | - Kelly S. Doran
- University of Colorado-Anschutz, Department of Immunology and Microbiology, Aurora, CO, USA
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6
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Bobrovskyy M, Chen X, Missiakas D. The Type 7b Secretion System of S. aureus and Its Role in Colonization and Systemic Infection. Infect Immun 2023; 91:e0001523. [PMID: 37039657 PMCID: PMC10187124 DOI: 10.1128/iai.00015-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 03/14/2023] [Indexed: 04/12/2023] Open
Abstract
Staphylococcus aureus bears a type 7b secretion system (T7bSS) that assembles in the bacterial envelope to promote the secretion of WXG-like proteins and toxic effectors bearing LXG domains. Cognate immunity proteins bind cytosolic effectors to mute their toxicity prior to secretion. T7b-secreted factors have been associated with the pathogenesis of staphylococcal disease and intraspecies competition. We identified earlier strain WU1, an S. aureus ST88 isolate that caused outbreaks of skin and soft tissue infections in mouse breeding facilities. WU1 was also found to persistently colonize the nasopharynx of animals, suggesting a strong host adaptation. In this manner, WU1 colonization and infectivity in mice resembles that of methicillin-sensitive and -resistant S. aureus strains in humans, where nasal carriage is a major risk factor for invasive infections. Here, animals were colonized with wild-type or T7-deficient WU1 strains or combinations thereof. Absence of the T7bSS did not affect colonization in the nasopharynx of animals, and although fluctuations were observed in weekly samplings, the wild-type strain did not replace the T7-deficient strain in cocolonization experiments. Bloodstream infection with a T7b-deficient strain resulted in enhanced survival and reduced bacterial loads and abscesses in soft tissues compared to infection with wild-type WU1. Together, experiments using a mouse-adapted strain suggest that the T7bSS of S. aureus is an important contributor to the pathogenesis of invasive disease.
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Affiliation(s)
- Maksym Bobrovskyy
- Department of Microbiology, University of Chicago, Chicago, Illinois, USA
| | - Xinhai Chen
- Howard Taylor Ricketts Laboratory, University of Chicago, Lemont, Illinois, USA
| | - Dominique Missiakas
- Department of Microbiology, University of Chicago, Chicago, Illinois, USA
- Howard Taylor Ricketts Laboratory, University of Chicago, Lemont, Illinois, USA
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7
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Spencer BL, Job AM, Robertson CM, Hameed ZA, Serchejian C, Wiafe-Kwakye CS, Mendonça JC, Apolonio MA, Nagao PE, Neely MN, Korotkova N, Korotkov KV, Patras KA, Doran KS. Heterogeneity of the group B streptococcal type VII secretion system and influence on colonization of the female genital tract. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.25.525443. [PMID: 36747681 PMCID: PMC9900821 DOI: 10.1101/2023.01.25.525443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Type VIIb secretion systems (T7SSb) in Gram-positive bacteria facilitate physiology, interbacterial competition, and/or virulence via EssC ATPase-driven secretion of small ɑ-helical proteins and toxins. Recently, we characterized T7SSb in group B Streptococcus (GBS), a leading cause of infection in newborns and immunocompromised adults. GBS T7SS comprises four subtypes based on variation in the C-terminus of EssC and the repertoire of downstream effectors; however, the intra-species diversity of GBS T7SS and impact on GBS-host interactions remains unknown. Bioinformatic analysis indicates that GBS T7SS loci encode subtype-specific putative effectors, which have low inter-species and inter-subtype homology but contain similar domains/motifs and therefore may serve similar functions. We further identify orphaned GBS WXG100 proteins. Functionally, we show that GBS T7SS subtype I and III strains secrete EsxA in vitro and that in subtype I strain CJB111, esxA1 appears to be differentially transcribed from the T7SS operon. Further, we observe subtype-specific effects of GBS T7SS on host colonization, as subtype I but not subtype III T7SS promotes GBS vaginal persistence. Finally, we observe that T7SS subtypes I and II are the predominant subtypes in clinical GBS isolates. This study highlights the potential impact of T7SS heterogeneity on host-GBS interactions.
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Affiliation(s)
- Brady L. Spencer
- University of Colorado-Anschutz, Department of Immunology and Microbiology, Aurora, CO, USA
| | - Alyx M. Job
- University of Colorado-Anschutz, Department of Immunology and Microbiology, Aurora, CO, USA
| | - Clare M. Robertson
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Zainab A. Hameed
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Camille Serchejian
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | | | - Jéssica C. Mendonça
- University of Colorado-Anschutz, Department of Immunology and Microbiology, Aurora, CO, USA
- Rio de Janeiro State University, Roberto Alcantara Gomes Biology Institute, Rio de Janeiro, RJ, Brazil
| | - Morgan A. Apolonio
- University of Colorado-Anschutz, Department of Immunology and Microbiology, Aurora, CO, USA
- National Summer Undergraduate Research Program, University of Arizona, Tucson, AZ, USA
| | - Prescilla E. Nagao
- Rio de Janeiro State University, Roberto Alcantara Gomes Biology Institute, Rio de Janeiro, RJ, Brazil
| | - Melody N. Neely
- University of Maine, Molecular & Biomedical Sciences, Orono, ME, USA
| | - Natalia Korotkova
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky, Lexington, KY, USA
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, USA
| | - Konstantin V. Korotkov
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, USA
| | - Kathryn A. Patras
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
- Alkek Center for Metagenomics and Microbiome Research, Baylor College of Medicine, Houston, TX, USA
| | - Kelly S. Doran
- University of Colorado-Anschutz, Department of Immunology and Microbiology, Aurora, CO, USA
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8
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Wang Y, Zhou Y, Shi C, Liu J, Lv G, Huang H, Li S, Duan L, Zheng X, Liu Y, Zhou H, Wang Y, Li Z, Ding K, Sun P, Huang Y, Lu X, Zhang ZM. A toxin-deformation dependent inhibition mechanism in the T7SS toxin-antitoxin system of Gram-positive bacteria. Nat Commun 2022; 13:6434. [PMID: 36307446 PMCID: PMC9616950 DOI: 10.1038/s41467-022-34034-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2021] [Accepted: 10/11/2022] [Indexed: 12/25/2022] Open
Abstract
Toxin EsaD secreted by some S. aureus strains through the type VII secretion system (T7SS) specifically kills those strains lacking the antitoxin EsaG. Here we report the structures of EsaG, the nuclease domain of EsaD and their complex, which together reveal an inhibition mechanism that relies on significant conformational change of the toxin. To inhibit EsaD, EsaG breaks the nuclease domain of EsaD protein into two independent fragments that, in turn, sandwich EsaG. The originally well-folded ββα-metal finger connecting the two fragments is stretched to become a disordered loop, leading to disruption of the catalytic site of EsaD and loss of nuclease activity. This mechanism is distinct from that of the other Type II toxin-antitoxin systems, which utilize an intrinsically disordered region on the antitoxins to cover the active site of the toxins. This study paves the way for developing therapeutic approaches targeting this antagonism.
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Affiliation(s)
- Yongjin Wang
- grid.258164.c0000 0004 1790 3548International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of Pharmacy, Jinan University, Guangzhou, 510632 China
| | - Yang Zhou
- grid.258164.c0000 0004 1790 3548International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of Pharmacy, Jinan University, Guangzhou, 510632 China
| | - Chaowei Shi
- grid.59053.3a0000000121679639Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, 230026 China
| | - Jiacong Liu
- grid.258164.c0000 0004 1790 3548International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of Pharmacy, Jinan University, Guangzhou, 510632 China
| | - Guohua Lv
- grid.258164.c0000 0004 1790 3548Division of Histology & Embryology, Medical College, Jinan University, Guangzhou, 510632 China
| | - Huisi Huang
- grid.258164.c0000 0004 1790 3548International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of Pharmacy, Jinan University, Guangzhou, 510632 China
| | - Shengrong Li
- grid.258164.c0000 0004 1790 3548International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of Pharmacy, Jinan University, Guangzhou, 510632 China
| | - Liping Duan
- grid.258164.c0000 0004 1790 3548International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of Pharmacy, Jinan University, Guangzhou, 510632 China
| | - Xinyi Zheng
- grid.258164.c0000 0004 1790 3548International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of Pharmacy, Jinan University, Guangzhou, 510632 China
| | - Yue Liu
- grid.258164.c0000 0004 1790 3548International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of Pharmacy, Jinan University, Guangzhou, 510632 China
| | - Haibo Zhou
- grid.258164.c0000 0004 1790 3548International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of Pharmacy, Jinan University, Guangzhou, 510632 China
| | - Yonghua Wang
- grid.79703.3a0000 0004 1764 3838School of Food Science and Engineering, South China University of Technology, Guangzhou, 510640 China
| | - Zhengqiu Li
- grid.258164.c0000 0004 1790 3548International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of Pharmacy, Jinan University, Guangzhou, 510632 China
| | - Ke Ding
- grid.258164.c0000 0004 1790 3548International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of Pharmacy, Jinan University, Guangzhou, 510632 China
| | - Pinghua Sun
- grid.258164.c0000 0004 1790 3548International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of Pharmacy, Jinan University, Guangzhou, 510632 China
| | - Yun Huang
- grid.5386.8000000041936877XDepartment of Physiology & Biophysics, Weill Cornell Medicine, New York, NY 10065 USA
| | - Xiaoyun Lu
- grid.258164.c0000 0004 1790 3548International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of Pharmacy, Jinan University, Guangzhou, 510632 China
| | - Zhi-Min Zhang
- grid.258164.c0000 0004 1790 3548International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of Pharmacy, Jinan University, Guangzhou, 510632 China ,Guangdong Youmei Institute of Intelligent Bio-manufacturing, Foshan, Guangdong 528200 China
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9
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The Antibacterial Type VII Secretion System of Bacillus subtilis: Structure and Interactions of the Pseudokinase YukC/EssB. mBio 2022; 13:e0013422. [PMID: 36154281 PMCID: PMC9600267 DOI: 10.1128/mbio.00134-22] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Type VIIb secretion systems (T7SSb) were recently proposed to mediate different aspects of Firmicutes physiology, including bacterial pathogenicity and competition. However, their architecture and mechanism of action remain largely obscure. Here, we present a detailed analysis of the T7SSb-mediated bacterial competition in Bacillus subtilis, using the effector YxiD as a model for the LXG secreted toxins. By systematically investigating protein-protein interactions, we reveal that the membrane subunit YukC contacts all T7SSb components, including the WXG100 substrate YukE and the LXG effector YxiD. YukC’s crystal structure shows unique features, suggesting an intrinsic flexibility that is required for T7SSb antibacterial activity. Overall, our results shed light on the role and molecular organization of the T7SSb and demonstrate the potential of B. subtilis as a model system for extensive structure-function studies of these secretion machineries.
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10
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Garrett SR, Mariano G, Dicks J, Palmer T. Homologous recombination between tandem paralogues drives evolution of a subset of type VII secretion system immunity genes in firmicute bacteria. Microb Genom 2022; 8. [PMID: 35960642 PMCID: PMC9484751 DOI: 10.1099/mgen.0.000868] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The type VII secretion system (T7SS) is found in many Gram-positive firmicutes and secretes protein toxins that mediate bacterial antagonism. Two T7SS toxins have been identified in Staphylococcus aureus, EsaD a nuclease toxin that is counteracted by the EsaG immunity protein, and TspA, which has membrane depolarising activity and is neutralised by TsaI. Both toxins are polymorphic, and strings of non-identical esaG and tsaI immunity genes are encoded in all S. aureus strains. To investigate the evolution of esaG repertoires, we analysed the sequences of the tandem esaG genes and their encoded proteins. We identified three blocks of high sequence similarity shared by all esaG genes and identified evidence of extensive recombination events between esaG paralogues facilitated through these conserved sequence blocks. Recombination between these blocks accounts for loss and expansion of esaG genes in S. aureus genomes and we identified evidence of such events during evolution of strains in clonal complex 8. TipC, an immunity protein for the TelC lipid II phosphatase toxin secreted by the streptococcal T7SS, is also encoded by multiple gene paralogues. Two blocks of high sequence similarity locate to the 5′ and 3′ end of tipC genes, and we found strong evidence for recombination between tipC paralogues encoded by Streptococcus mitis BCC08. By contrast, we found only a single homology block across tsaI genes, and little evidence for intergenic recombination within this gene family. We conclude that homologous recombination is one of the drivers for the evolution of T7SS immunity gene clusters.
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Affiliation(s)
- Stephen R Garrett
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Giuseppina Mariano
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Jo Dicks
- Culture Collections, UK Health Security Agency, 61 Colindale Ave, London, NW9 5EQ, UK
| | - Tracy Palmer
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
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11
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Bobrovskyy M, Oh SY, Missiakas D. Contribution of the EssC ATPase to the assembly of the type 7b secretion system in Staphylococcus aureus. J Biol Chem 2022; 298:102318. [PMID: 35921891 PMCID: PMC9436818 DOI: 10.1016/j.jbc.2022.102318] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 07/07/2022] [Accepted: 07/13/2022] [Indexed: 11/28/2022] Open
Abstract
Secretion systems utilize ATPase activity to facilitate the translocation of proteins into and across membranes. In bacteria, the universally conserved SecA ATPase binds a large repertoire of preproteins and interacts with the SecYEG translocon. In contrast, the type 7b secretion system (T7bSS) of Staphylococcus aureus supports the secretion of a restricted subset of proteins. T7bSSs are found in several Firmicutes as gene clusters encoding secreted WXG100 proteins and FtsK/SpoIIIE-like ATPase. In S. aureus, this ATPase is called EssC and comprises two cytosolic forkhead-associated domains (FHA1–2), two membrane-spanning segments (TM1–2), and four cytosolic modules named DUF (domain of unknown function) and ATPases1-3 (D1D2D3). However, a detailed understanding of the interactions of EssC in the T7bSS is not clear. Here, we tagged EssC and performed affinity chromatography of detergent-solubilized extracts of wild type and isogenic mutants of S. aureus. We found that EssC recruits EsaA, EssA, and EssB in a complex referred to as the ESS (ESAT-6 like secretion system) translocon, and secreted substrates were not required for translocon assembly. Furthermore, deletions of FHA1 and DUF rendered EssC unstable, whereas FHA2 was required for association with EssB. This interaction was independent of EsaA, but EsaA was required to recruit EssA to the EssC–EssB complex. Finally, we show that assembly of the ESS translocon was impaired upon mutation of D2 structural motifs. Together, our data indicate that the ESS translocon is maintained fully assembled at the plasma membrane and that D2 is fundamental in sustaining the integrity of this complex.
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Affiliation(s)
- Maksym Bobrovskyy
- Department of Microbiology, University of Chicago, Chicago, Illinois, USA
| | - So Young Oh
- Howard Taylor Ricketts Laboratory, University of Chicago, Lemont, Illinois, USA
| | - Dominique Missiakas
- Department of Microbiology, University of Chicago, Chicago, Illinois, USA; Howard Taylor Ricketts Laboratory, University of Chicago, Lemont, Illinois, USA.
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12
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Jain S, Bhowmick A, Jeong B, Bae T, Ghosh A. Unravelling the physiological roles of mazEF toxin-antitoxin system on clinical MRSA strain by CRISPR RNA-guided cytidine deaminase. J Biomed Sci 2022; 29:28. [PMID: 35524246 PMCID: PMC9077811 DOI: 10.1186/s12929-022-00810-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 04/22/2022] [Indexed: 12/13/2022] Open
Abstract
Background Curiosity on toxin–antitoxin modules has increased intensely over recent years as it is ubiquitously present in many bacterial genomes, including pathogens like Methicillin-resistant Staphylococcus aureus (MRSA). Several cellular functions of TA systems have been proposed however, their exact role in cellular physiology remains unresolved. Methods This study aims to find out the impact of the mazEF toxin–antitoxin module on biofilm formation, pathogenesis, and antibiotic resistance in an isolated clinical ST239 MRSA strain, by constructing mazE and mazF mutants using CRISPR–cas9 base-editing plasmid (pnCasSA-BEC). Transcriptome analysis (RNA-seq) was performed for the mazE antitoxin mutant in order to identify the differentially regulated genes. The biofilm formation was also assessed for the mutant strains. Antibiogram profiling was carried out for both the generated mutants followed by murine experiment to determine the pathogenicity of the constructed strains. Results For the first time our work showed, that MazF promotes cidA mediated cell death and lysis for biofilm formation without playing any significant role in host virulence as suggested by the murine experiment. Interestingly, the susceptibility to oxacillin, daptomycin and vancomycin was reduced significantly by the activated MazF toxin in the mazE mutant strain. Conclusions Our study reveals that activated MazF toxin leads to resistance to antibiotics like oxacillin, daptomycin and vancomycin. Therefore, in the future, any potential antibacterial drug can be designed to target MazF toxin against the problematic multi-drug resistant bug. Supplementary Information The online version contains supplementary material available at 10.1186/s12929-022-00810-5.
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Affiliation(s)
- Sonia Jain
- Infectious Disease and Immunology Division, CSIR-Indian Institute of Chemical Biology, Kolkata, 700032, India.
| | - Arghya Bhowmick
- Department of Biochemistry, Bose Institute, EN Block, Sector-V, Kolkata, 700091, India
| | - Bohyun Jeong
- Department of Microbiology, Kosin University College of Medicine, Busan, 49267, South Korea
| | - Taeok Bae
- Department of Microbiology and Immunology, Indiana University, School of Medicine-Northwest, Gary, IN, 46408-1197, USA
| | - Abhrajyoti Ghosh
- Department of Biochemistry, Bose Institute, EN Block, Sector-V, Kolkata, 700091, India.
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13
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Garcia Gonzalez J, Hernandez FJ. Nuclease activity: an exploitable biomarker in bacterial infections. Expert Rev Mol Diagn 2022; 22:265-294. [PMID: 35240900 DOI: 10.1080/14737159.2022.2049249] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
INTRODUCTION In the increasingly challenging field of clinical microbiology, diagnosis is a cornerstone whose accuracy and timing are crucial for the successful management, therapy, and outcome of infectious diseases. Currently employed biomarkers of infectious diseases define the scope and limitations of diagnostic techniques. As such, expanding the biomarker catalog is crucial to address unmet needs and bring about novel diagnostic functionalities and applications. AREAS COVERED This review describes the extracellular nucleases of 15 relevant bacterial pathogens and discusses the potential use of nuclease activity as a diagnostic biomarker. Articles were searched for in PubMed using terms: "nuclease", "bacteria", "nuclease activity" or "biomarker". For overview sections, original and review articles between 2000 and 2019 were searched for using terms: "infections", "diagnosis", "bacterial", "burden", "challenges". Informative articles were selected. EXPERT OPINION Using the catalytic activity of nucleases offers new possibilities compared to established biomarkers. Nucleic acid activatable reporters in combination with different transduction platforms and delivery methods can be used to detect disease-associated nuclease activity patterns in vitro and in vivo for prognostic and diagnostic applications. Even when these patterns are not obvious or of unknown etiology, screening platforms could be used to identify new disease reporters.
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Affiliation(s)
- Javier Garcia Gonzalez
- Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.,Wallenberg Centre for Molecular Medicine (WCMM), Linköping, Sweden.,Nucleic Acids Technologies Laboratory (NAT-lab), Linköping University, Linköping, Sweden
| | - Frank J Hernandez
- Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.,Wallenberg Centre for Molecular Medicine (WCMM), Linköping, Sweden.,Nucleic Acids Technologies Laboratory (NAT-lab), Linköping University, Linköping, Sweden
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14
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von Köckritz-Blickwede M, Winstel V. Molecular Prerequisites for Neutrophil Extracellular Trap Formation and Evasion Mechanisms of Staphylococcus aureus. Front Immunol 2022; 13:836278. [PMID: 35237275 PMCID: PMC8884242 DOI: 10.3389/fimmu.2022.836278] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 01/19/2022] [Indexed: 12/15/2022] Open
Abstract
NETosis is a multi-facetted cellular process that promotes the formation of neutrophil extracellular traps (NETs). NETs as web-like structures consist of DNA fibers armed with granular proteins, histones, and microbicidal peptides, thereby exhibiting pathogen-immobilizing and antimicrobial attributes that maximize innate immune defenses against invading microbes. However, clinically relevant pathogens often tolerate entrapment and even take advantage of the remnants of NETs to cause persistent infections in mammalian hosts. Here, we briefly summarize how Staphylococcus aureus, a high-priority pathogen and causative agent of fatal diseases in humans as well as animals, catalyzes and concurrently exploits NETs during pathogenesis and recurrent infections. Specifically, we focus on toxigenic and immunomodulatory effector molecules produced by staphylococci that prime NET formation, and further highlight the molecular and underlying principles of suicidal NETosis compared to vital NET-formation by viable neutrophils in response to these stimuli. We also discuss the inflammatory potential of NET-controlled microenvironments, as excessive expulsion of NETs from activated neutrophils provokes local tissue injury and may therefore amplify staphylococcal disease severity in hospitalized or chronically ill patients. Combined with an overview of adaptation and counteracting strategies evolved by S. aureus to impede NET-mediated killing, these insights may stimulate biomedical research activities to uncover novel aspects of NET biology at the host-microbe interface.
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Affiliation(s)
- Maren von Köckritz-Blickwede
- Department of Biochemistry, University of Veterinary Medicine Hannover, Hannover, Germany
- Research Center for Emerging Infections and Zoonoses (RIZ), University of Veterinary Medicine Hannover, Hannover, Germany
| | - Volker Winstel
- Research Group Pathogenesis of Bacterial Infections, TWINCORE, Centre for Experimental and Clinical Infection Research, a joint venture between the Hannover Medical School and the Helmholtz Centre for Infection Research, Hannover, Germany
- Institute of Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Hannover, Germany
- *Correspondence: Volker Winstel,
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15
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Li H, Tan Y, Zhang D. Genomic discovery and structural dissection of a novel type of polymorphic toxin system in gram-positive bacteria. Comput Struct Biotechnol J 2022; 20:4517-4531. [PMID: 36051883 PMCID: PMC9424270 DOI: 10.1016/j.csbj.2022.08.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Revised: 08/15/2022] [Accepted: 08/15/2022] [Indexed: 11/26/2022] Open
Abstract
Bacteria have developed several molecular conflict systems to facilitate kin recognition and non-kin competition to gain advantages in the acquisition of growth niches and of limited resources. One such example is a large class of so-called polymorphic toxin systems (PTSs), which comprise a variety of the toxin proteins secreted via T2SS, T5SS, T6SS, T7SS and many others. These systems are highly divergent in terms of sequence/structure, domain architecture, toxin-immunity association, and organization of the toxin loci, which makes it difficult to identify and characterize novel systems using traditional experimental and bioinformatic strategies. In recent years, we have been developing and utilizing unique genome-mining strategies and pipelines, based on the organizational principles of both domain architectures and genomic loci of PTSs, for an effective and comprehensive discovery of novel PTSs, dissection of their components, and prediction of their structures and functions. In this study, we present our systematic discovery of a new type of PTS (S8-PTS) in several gram-positive bacteria. We show that the S8-PTS contains three components: a peptidase of the S8 family (subtilases), a polymorphic toxin, and an immunity protein. We delineated the typical organization of these polymorphic toxins, in which a N-terminal signal peptide is followed by a potential receptor binding domain, BetaH, and one of 16 toxin domains. We classified each toxin domain by the distinct superfamily to which it belongs, identifying nine BECR ribonucleases, one Restriction Endonuclease, one HNH nuclease, two novel toxin domains homologous to the VOC enzymes, one toxin domain with the Frataxin-like fold, and several other unique toxin families such as Ntox33 and HicA. Accordingly, we identified 20 immunity families and classified them into different classes of folds. Further, we show that the S8-PTS-associated peptidases are analogous to many other processing peptidases found in T5SS, T7SS, T9SS, and many proprotein-processing peptidases, indicating that they function to release the toxin domains during secretion. The S8-PTSs are mostly found in animal and plant-associated bacteria, including many pathogens. We propose S8-PTSs will facilitate the competition of these bacteria with other microbes or contribute to the pathogen-host interactions.
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Affiliation(s)
- Huan Li
- Department of Biology, College of Arts & Sciences, Saint Louis University, Saint Louis, MO 63103, USA
| | - Yongjun Tan
- Department of Biology, College of Arts & Sciences, Saint Louis University, Saint Louis, MO 63103, USA
| | - Dapeng Zhang
- Department of Biology, College of Arts & Sciences, Saint Louis University, Saint Louis, MO 63103, USA
- Program of Bioinformatics and Computational Biology, College of Arts & Sciences, Saint Louis University, MO 63103, USA
- Corresponding author at: Department of Biology, College of Arts & Sciences, Saint Louis University, Saint Louis, MO 63103, USA.
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16
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Early development of the skin microbiome: therapeutic opportunities. Pediatr Res 2021; 90:731-737. [PMID: 32919387 PMCID: PMC7952468 DOI: 10.1038/s41390-020-01146-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 07/23/2020] [Accepted: 08/16/2020] [Indexed: 02/06/2023]
Abstract
As human skin hosts a diverse microbiota in health and disease, there is an emerging consensus that dysregulated interactions between host and microbiome may contribute to chronic inflammatory disease of the skin. Neonatal skin is a unique habitat, structurally similar to the adult but with a different profile of metabolic substrates, environmental stressors, and immune activity. The surface is colonized within moments of birth with a bias toward maternal strains. Initial colonists are outcompeted as environmental exposures increase and host skin matures. Nonetheless, early life microbial acquisitions may have long-lasting effects on health through modulation of host immunity and competitive interactions between bacteria. Microbial ecology and its influence on health have been of interest to dermatologists for >50 years, and an explosion of recent interest in the microbiome has prompted ongoing investigations of several microbial therapeutics for dermatological disease. In this review, we consider how recent insight into the host and microbial factors driving development of the skin microbiome in early life offers new opportunities for therapeutic intervention. IMPACT: Advancement in understanding molecular mechanisms of bacterial competition opens new avenues of investigation into dermatological disease. Primary development of the skin microbiome is determined by immunological features of the cutaneous habitat. Understanding coordinated microbial and immunological development in the pediatric patient requires a multidisciplinary synthesis of primary literature.
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17
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Abstract
The type VII protein secretion system (T7SS) of Staphylococcus aureus is encoded at the ess locus. T7 substrate recognition and protein transport are mediated by EssC, a membrane-bound multidomain ATPase. Four EssC sequence variants have been identified across S. aureus strains, each accompanied by a specific suite of substrate proteins. The ess genes are upregulated during persistent infection, and the secretion system contributes to virulence in disease models. It also plays a key role in intraspecies competition, secreting nuclease and membrane-depolarizing toxins that inhibit the growth of strains lacking neutralizing immunity proteins. A genomic survey indicates that the T7SS is widely conserved across staphylococci and is encoded in clusters that contain diverse arrays of toxin and immunity genes. The presence of genomic islands encoding multiple immunity proteins in species such as Staphylococcus warneri that lack the T7SS points to a major role for the secretion system in bacterial antagonism. Expected final online publication date for the Annual Review of Microbiology, Volume 75 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Lisa Bowman
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, United Kingdom; ,
| | - Tracy Palmer
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, United Kingdom; ,
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18
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Soe YM, Bedoui S, Stinear TP, Hachani A. Intracellular Staphylococcus aureus and host cell death pathways. Cell Microbiol 2021; 23:e13317. [PMID: 33550697 DOI: 10.1111/cmi.13317] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 01/22/2021] [Accepted: 01/23/2021] [Indexed: 12/13/2022]
Abstract
Staphylococcus aureus is a major opportunistic human pathogen that is globally prevalent. Although S. aureus and humans may have co-evolved to the point of commensalism, the bacterium is equipped with virulence factors causing devastating infections. The adoption of an intracellular lifestyle by S. aureus is an important facet of its pathogenesis. Occupying a privileged intracellular compartment permits evasion from the bactericidal actions of host immunity and antibiotics. However, this localization exposes S. aureus to cell-intrinsic processes comprising autophagy, metabolic challenges and clearance mechanisms orchestrated by host programmed cell death pathways (PCDs), including apoptosis, pyroptosis and necroptosis. Mounting evidence suggests that S. aureus deploys pathoadaptive mechanisms that modulate the expression of its virulence factors to prevent elimination through PCD pathways. In this review, we critically analyse the current literature on the interplay between S. aureus virulence factors with the key, intertwined nodes of PCD. We discuss how S. aureus adaptation to the human host plays an essential role in the evasion of PCD, and we consider future directions to study S. aureus-PCD interactions.
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Affiliation(s)
- Ye Mon Soe
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
| | - Sammy Bedoui
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
| | - Timothy P Stinear
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
| | - Abderrahman Hachani
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
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19
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Bowran K, Palmer T. Extreme genetic diversity in the type VII secretion system of Listeria monocytogenes suggests a role in bacterial antagonism. MICROBIOLOGY-SGM 2021; 167. [PMID: 33599605 DOI: 10.1099/mic.0.001034] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The type VII protein secretion system (T7SS) has been characterized in members of the phyla Actinobacteria and Firmicutes. In mycobacteria the T7SS is intimately linked with pathogenesis and intracellular survival, while in Firmicutes there is mounting evidence that the system plays a key role in interbacterial competition. A conserved membrane-bound ATPase protein, termed EssC in Staphylococcus aureus, is a critical component of the T7SS and is the primary receptor for substrate proteins. Genetic diversity in the essC gene of S. aureus has previously been reported, resulting in four protein variants that are linked to specific subsets of substrates. Here we have analysed the genetic diversity of the T7SS-encoding genes and substrate proteins across Listeria monocytogenes genome sequences. We find that there are seven EssC variants across the species that differ in their C-terminal region; each variant is correlated with a distinct subset of genes for likely substrate and accessory proteins. EssC1 is most common and is exclusively linked with polymorphic toxins harbouring a YeeF domain, whereas EssC5, EssC6 and EssC7 variants all code for an LXG domain protein adjacent to essC. Some essC1 variant strains encode an additional, truncated essC at their T7 gene cluster. The truncated EssC, comprising only the C-terminal half of the protein, matches the sequence of either EssC2, EssC3 or EssC4. In each case the truncated gene directly precedes a cluster of substrate/accessory protein genes acquired from the corresponding strain. Across L. monocytogenes strains we identified 40 LXG domain proteins, most of which are encoded at conserved genomic loci. These loci also harbour genes encoding immunity proteins and sometimes additional toxin fragments. Collectively our findings strongly suggest that the T7SS plays an important role in bacterial antagonism in this species.
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Affiliation(s)
- Kieran Bowran
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Tracy Palmer
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
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20
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Tran HKR, Grebenc DW, Klein TA, Whitney JC. Bacterial type VII secretion: An important player in host-microbe and microbe-microbe interactions. Mol Microbiol 2021; 115:478-489. [PMID: 33410158 DOI: 10.1111/mmi.14680] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Revised: 01/03/2021] [Accepted: 01/04/2021] [Indexed: 12/19/2022]
Abstract
Type VII secretion systems (T7SSs) are poorly understood protein export apparatuses found in mycobacteria and many species of Gram-positive bacteria. To date, this pathway has predominantly been studied in Mycobacterium tuberculosis, where it has been shown to play an essential role in virulence; however, much less studied is an evolutionarily divergent subfamily of T7SSs referred to as the T7SSb. The T7SSb is found in the major Gram-positive phylum Firmicutes where it was recently shown to target both eukaryotic and prokaryotic cells, suggesting a dual role for this pathway in host-microbe and microbe-microbe interactions. In this review, we compare the current understanding of the molecular architectures and substrate repertoires of the well-studied mycobacterial T7SSa systems to that of recently characterized T7SSb pathways and highlight how these differences may explain the observed biological functions of this understudied protein export machine.
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Affiliation(s)
- Hiu-Ki R Tran
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada.,Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada
| | - Dirk W Grebenc
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada.,Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada
| | - Timothy A Klein
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada.,Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada
| | - John C Whitney
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada.,Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada.,David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, ON, Canada
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21
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Taylor JC, Gao X, Xu J, Holder M, Petrosino J, Kumar R, Liu W, Höök M, Mackenzie C, Hillhouse A, Brashear W, Nunez MP, Xu Y. A type VII secretion system of Streptococcus gallolyticus subsp. gallolyticus contributes to gut colonization and the development of colon tumors. PLoS Pathog 2021; 17:e1009182. [PMID: 33406160 PMCID: PMC7815207 DOI: 10.1371/journal.ppat.1009182] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 01/19/2021] [Accepted: 11/23/2020] [Indexed: 02/06/2023] Open
Abstract
Streptococcus gallolyticus subspecies gallolyticus (Sgg) has a strong clinical association with colorectal cancer (CRC) and actively promotes the development of colon tumors. However, the molecular determinants involved in Sgg pathogenicity in the gut are unknown. Bacterial type VII secretion systems (T7SS) mediate pathogen interactions with their host and are important for virulence in pathogenic mycobacteria and Staphylococcus aureus. Through genome analysis, we identified a locus in Sgg strain TX20005 that encodes a putative type VII secretion system (designated as SggT7SST05). We showed that core genes within the SggT7SST05 locus are expressed in vitro and in the colon of mice. Western blot analysis showed that SggEsxA, a protein predicted to be a T7SS secretion substrate, is detected in the bacterial culture supernatant, indicating that this SggT7SST05 is functional. Deletion of SggT7SST05 (TX20005Δesx) resulted in impaired bacterial adherence to HT29 cells and abolished the ability of Sgg to stimulate HT29 cell proliferation. Analysis of bacterial culture supernatants suggest that SggT7SST05-secreted factors are responsible for the pro-proliferative activity of Sgg, whereas Sgg adherence to host cells requires both SggT7SST05-secreted and bacterial surface-associated factors. In a murine gut colonization model, TX20005Δesx showed significantly reduced colonization compared to the parent strain. Furthermore, in a mouse model of CRC, mice exposed to TX20005 had a significantly higher tumor burden compared to saline-treated mice, whereas those exposed to TX20005Δesx did not. Examination of the Sgg load in the colon in the CRC model suggests that SggT7SST05-mediated activities are directly involved in the promotion of colon tumors. Taken together, these results reveal SggT7SST05 as a previously unrecognized pathogenicity determinant for Sgg colonization of the colon and promotion of colon tumors. Colorectal cancer (CRC) is a leading cause of cancer-related death. The development of CRC can be strongly influenced by specific gut microbes. Understanding how gut microbes modulate CRC is critical to developing novel strategies to improve clinical diagnosis and treatment of this disease. S. gallolyticus subsp. gallolyticus (Sgg) has a strong clinical association with CRC and actively promotes the development of colon tumors. However, the specific Sgg molecules that mediate its pro-tumor activity are unknown. Here we report the first characterization of a type VII secretion system (T7SS) in Sgg, designated as SggT7SST05. We further demonstrate that SggT7SST05-mediated activities are important for Sgg to colonize the colon and to promote the development of colon tumors. These findings reveal SggT7SST05 as a novel pathogenicity determinant of Sgg and provide a critical breakthrough in our efforts to understand how Sgg influences the development of CRC. Future investigations of the biological activities of specific effectors of SggT7SST05 will likely lead to the discovery of Sgg molecules that can be used as diagnostic markers and intervention targets aimed at mitigating the harmful effect of Sgg.
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Affiliation(s)
- John Culver Taylor
- Center for Infectious and Inflammatory Diseases, Texas A&M Health Science Center Institute of Biosciences of Technology, Houston, Texas, United States of America
| | - Xinsheng Gao
- Center for Infectious and Inflammatory Diseases, Texas A&M Health Science Center Institute of Biosciences of Technology, Houston, Texas, United States of America
| | - Juan Xu
- Center for Infectious and Inflammatory Diseases, Texas A&M Health Science Center Institute of Biosciences of Technology, Houston, Texas, United States of America
| | - Michael Holder
- Center for Metagenomics and Microbiome Research, Baylor College of Medicine, Houston, Texas, United States of America
| | - Joseph Petrosino
- Center for Metagenomics and Microbiome Research, Baylor College of Medicine, Houston, Texas, United States of America
| | - Ritesh Kumar
- Center for Infectious and Inflammatory Diseases, Texas A&M Health Science Center Institute of Biosciences of Technology, Houston, Texas, United States of America
| | - Wen Liu
- Center for Infectious and Inflammatory Diseases, Texas A&M Health Science Center Institute of Biosciences of Technology, Houston, Texas, United States of America
| | - Magnus Höök
- Center for Infectious and Inflammatory Diseases, Texas A&M Health Science Center Institute of Biosciences of Technology, Houston, Texas, United States of America
| | - Chris Mackenzie
- Department of Microbiology and Molecular Genetics, McGovern Medical School, UT Health, Houston, Texas, United States of America
| | - Andrew Hillhouse
- Texas A&M Institute for Genome Sciences and Society, Texas A&M, Texas, United States of America
| | - Wesley Brashear
- Texas A&M Institute for Genome Sciences and Society, Texas A&M, Texas, United States of America
| | - Maria Patricia Nunez
- Center for Infectious and Inflammatory Diseases, Texas A&M Health Science Center Institute of Biosciences of Technology, Houston, Texas, United States of America
| | - Yi Xu
- Center for Infectious and Inflammatory Diseases, Texas A&M Health Science Center Institute of Biosciences of Technology, Houston, Texas, United States of America
- Department of Microbiology and Molecular Genetics, McGovern Medical School, UT Health, Houston, Texas, United States of America
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M Health Science Center, Texas, United States of America
- * E-mail:
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Klein TA, Grebenc DW, Gandhi SY, Shah VS, Kim Y, Whitney JC. Structure of the Extracellular Region of the Bacterial Type VIIb Secretion System Subunit EsaA. Structure 2020; 29:177-185.e6. [PMID: 33238147 DOI: 10.1016/j.str.2020.11.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 10/17/2020] [Accepted: 11/02/2020] [Indexed: 12/15/2022]
Abstract
Gram-positive bacteria use type VII secretion systems (T7SSs) to export effector proteins that manipulate the physiology of nearby prokaryotic and eukaryotic cells. Several mycobacterial T7SSs have established roles in virulence. By contrast, the genetically distinct T7SSb pathway found in Firmicutes bacteria more often functions to mediate bacterial competition. A lack of structural information on the T7SSb has limited the understanding of effector export by this protein secretion apparatus. Here, we present the 2.4 Å crystal structure of the extracellular region of the T7SSb subunit EsaA from Streptococcus gallolyticus. Our structure reveals that homodimeric EsaA is an elongated, arrow-shaped protein with a surface-accessible "tip", which in some species of bacteria serves as a receptor for lytic bacteriophages. Because it is the only T7SSb subunit large enough to traverse the peptidoglycan layer of Firmicutes, we propose that EsaA plays a critical role in transporting effectors across the entirety of the Gram-positive cell envelope.
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Affiliation(s)
- Timothy A Klein
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON L8S 4K1, Canada; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - Dirk W Grebenc
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON L8S 4K1, Canada; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - Shil Y Gandhi
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON L8S 4K1, Canada; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - Vraj S Shah
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON L8S 4K1, Canada; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - Youngchang Kim
- Structural Biology Center, X-ray Science, Argonne National Laboratory, Argonne, IL, USA
| | - John C Whitney
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON L8S 4K1, Canada; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4K1, Canada; David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, ON L8S 4K1, Canada.
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23
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Alhajjar N, Chatterjee A, Spencer BL, Burcham LR, Willett JLE, Dunny GM, Duerkop BA, Doran KS. Genome-Wide Mutagenesis Identifies Factors Involved in Enterococcus faecalis Vaginal Adherence and Persistence. Infect Immun 2020; 88:e00270-20. [PMID: 32778611 PMCID: PMC7504943 DOI: 10.1128/iai.00270-20] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 07/26/2020] [Indexed: 02/08/2023] Open
Abstract
Enterococcus faecalis is a Gram-positive commensal bacterium native to the gastrointestinal tract and an opportunistic pathogen of increasing clinical concern. E. faecalis also colonizes the female reproductive tract, and reports suggest vaginal colonization increases following antibiotic treatment or in patients with aerobic vaginitis. Currently, little is known about specific factors that promote E. faecalis vaginal colonization and subsequent infection. We modified an established mouse vaginal colonization model to explore E. faecalis vaginal carriage and demonstrate that both vancomycin-resistant and -sensitive strains colonize the murine vaginal tract. Following vaginal colonization, we observed E. faecalis in vaginal, cervical, and uterine tissue. A mutant lacking endocarditis- and biofilm-associated pili (Ebp) exhibited a decreased ability to associate with human vaginal and cervical cells in vitro but did not contribute to colonization in vivo Thus, we screened a low-complexity transposon (Tn) mutant library to identify novel genes important for E. faecalis colonization and persistence in the vaginal tract. This screen revealed 383 mutants that were underrepresented during vaginal colonization at 1, 5, and 8 days postinoculation compared to growth in culture medium. We confirmed that mutants deficient in ethanolamine catabolism or in the type VII secretion system were attenuated in persisting during vaginal colonization. These results reveal the complex nature of vaginal colonization and suggest that multiple factors contribute to E. faecalis persistence in the reproductive tract.
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Affiliation(s)
- Norhan Alhajjar
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | - Anushila Chatterjee
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | - Brady L Spencer
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | - Lindsey R Burcham
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | - Julia L E Willett
- Department of Microbiology and Immunology, University of Minnesota Medical School, Minneapolis, Minnesota, USA
| | - Gary M Dunny
- Department of Microbiology and Immunology, University of Minnesota Medical School, Minneapolis, Minnesota, USA
| | - Breck A Duerkop
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | - Kelly S Doran
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
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24
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The type VII secretion system protects Staphylococcus aureus against antimicrobial host fatty acids. Sci Rep 2020; 10:14838. [PMID: 32908165 PMCID: PMC7481793 DOI: 10.1038/s41598-020-71653-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 08/17/2020] [Indexed: 02/06/2023] Open
Abstract
The Staphylococcus aureus type VII secretion system (T7SS) exports several proteins that are pivotal for bacterial virulence. The mechanisms underlying T7SS-mediated staphylococcal survival during infection nevertheless remain unclear. Here we report that S. aureus lacking T7SS components are more susceptible to host-derived antimicrobial fatty acids. Unsaturated fatty acids such as linoleic acid (LA) elicited an increased inhibition of S. aureus mutants lacking T7SS effectors EsxC, EsxA and EsxB, or the membrane-bound ATPase EssC, compared to the wild-type (WT). T7SS mutants generated in different S. aureus strain backgrounds also displayed an increased sensitivity to LA. Analysis of bacterial membrane lipid profiles revealed that the esxC mutant was less able to incorporate LA into its membrane phospholipids. Although the ability to bind labelled LA did not differ between the WT and mutant strains, LA induced more cell membrane damage in the T7SS mutants compared to the WT. Furthermore, proteomic analyses of WT and mutant cell fractions revealed that, in addition to compromising membranes, T7SS defects induce oxidative stress and hamper their response to LA challenge. Thus, our findings indicate that T7SS contribute to maintaining S. aureus membrane integrity and homeostasis when bacteria encounter antimicrobial fatty acids.
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A membrane-depolarizing toxin substrate of the Staphylococcus aureus type VII secretion system mediates intraspecies competition. Proc Natl Acad Sci U S A 2020; 117:20836-20847. [PMID: 32769205 PMCID: PMC7456083 DOI: 10.1073/pnas.2006110117] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The type VII protein secretion system (T7SS) is conserved across Staphylococcus aureus strains and plays important roles in virulence and interbacterial competition. To date, only one T7SS substrate protein, encoded in a subset of S. aureus genomes, has been functionally characterized. Here, using an unbiased proteomic approach, we identify TspA as a further T7SS substrate. TspA is encoded distantly from the T7SS gene cluster and is found across all S. aureus strains as well as in Listeria and Enterococci. Heterologous expression of TspA from S. aureus strain RN6390 indicates its C-terminal domain is toxic when targeted to the Escherichia coli periplasm and that it depolarizes the cytoplasmic membrane. The membrane-depolarizing activity is alleviated by coproduction of the membrane-bound TsaI immunity protein, which is encoded adjacent to tspA on the S. aureus chromosome. Using a zebrafish hindbrain ventricle infection model, we demonstrate that the T7SS of strain RN6390 promotes bacterial replication in vivo, and deletion of tspA leads to increased bacterial clearance. The toxin domain of TspA is highly polymorphic and S. aureus strains encode multiple tsaI homologs at the tspA locus, suggestive of additional roles in intraspecies competition. In agreement, we demonstrate TspA-dependent growth inhibition of RN6390 by strain COL in the zebrafish infection model that is alleviated by the presence of TsaI homologs.
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26
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Ruhe ZC, Low DA, Hayes CS. Polymorphic Toxins and Their Immunity Proteins: Diversity, Evolution, and Mechanisms of Delivery. Annu Rev Microbiol 2020; 74:497-520. [PMID: 32680451 DOI: 10.1146/annurev-micro-020518-115638] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
All bacteria must compete for growth niches and other limited environmental resources. These existential battles are waged at several levels, but one common strategy entails the transfer of growth-inhibitory protein toxins between competing cells. These antibacterial effectors are invariably encoded with immunity proteins that protect cells from intoxication by neighboring siblings. Several effector classes have been described, each designed to breach the cell envelope of target bacteria. Although effector architectures and export pathways tend to be clade specific, phylogenetically distant species often deploy closely related toxin domains. Thus, diverse competition systems are linked through a common reservoir of toxin-immunity pairs that is shared via horizontal gene transfer. These toxin-immunity protein pairs are extraordinarily diverse in sequence, and this polymorphism underpins an important mechanism of self/nonself discrimination in bacteria. This review focuses on the structures, functions, and delivery mechanisms of polymorphic toxin effectors that mediate bacterial competition.
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Affiliation(s)
- Zachary C Ruhe
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA;
| | - David A Low
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA; .,Biomolecular Science and Engineering Program, University of California, Santa Barbara, California 93106, USA
| | - Christopher S Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA; .,Biomolecular Science and Engineering Program, University of California, Santa Barbara, California 93106, USA
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27
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Substrate Interaction with the EssC Coupling Protein of the Type VIIb Secretion System. J Bacteriol 2020; 202:JB.00646-19. [PMID: 31964696 DOI: 10.1128/jb.00646-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 01/08/2020] [Indexed: 01/05/2023] Open
Abstract
Staphylococcus aureus employs the type VIIb secretion system (T7SSb) to secrete effector proteins that either have antibacterial activities or promote bacterial persistence in mouse infection models. Here, we present the crystal structure of the ATPase domain D3 of the EssC coupling protein from S. aureus USA300_FPR3757, an integral component of the T7SSb complex, resolved at a 1.7-Å resolution. EssC-D3 shares structural homology with FtsK/SpoIII-like ATPase domains of T7SSa and T7SSb and exhibits a conserved pocket on the surface with differential amino acid composition. In T7SSa, substrate EsxB interacts with the D3 domain through this pocket. Here, we identify amino acids in this pocket that are essential for effector protein secretion in the T7SSb. Our results reveal that the adjacent ATPase domain D2 is a substrate binding site on EssC and that substrates bound to D2 require domain D3 for further transport. Point mutations in the Walker B motif of domain D3 have diametric effects on secretion activity, either abolishing or boosting it, pointing to a critical role of domain D3 in the substrate transport. Finally, we identify ATPase domain D3 as a virulence determinant of S. aureus USA300_FPR3757 using an invertebrate in vivo infection model.IMPORTANCE The emergence of antibiotic-resistant bacteria poses a rising problem in antibiotic treatment (S. Boyle-Vavra and R. S. Daum, Lab Invest 87:3-9, 2007, https://doi.org/10.1038/labinvest.3700501). We have used the multidrug-resistant S. aureus USA300_FPR3757 as a model organism to study the T7SSb. Effector proteins of this system have been associated with abscess formation and bacterial persistence in mouse models (M. L. Burts, A. C. DeDent, and D. M. Missiakas, Mol Microbiol 69:736-746, 2008, https://doi.org/10.1111/j.1365-2958.2008.06324.x; M. L. Burts, W. A. Williams, K. DeBord, and D. M. Missiakas, Proc Natl Acad Sci U S A 102:1169-1174, 2005, https://doi.org/10.1073/pnas.0405620102). We determined the structure of the essential ATPase domain D3 of the T7SSb at atomic resolution and validated a surface-exposed pocket as a potential drug target to block secretion. Furthermore, our study provides new mechanistic insights into the T7SSb substrate transport.
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Klein TA, Ahmad S, Whitney JC. Contact-Dependent Interbacterial Antagonism Mediated by Protein Secretion Machines. Trends Microbiol 2020; 28:387-400. [PMID: 32298616 DOI: 10.1016/j.tim.2020.01.003] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2019] [Revised: 12/18/2019] [Accepted: 01/16/2020] [Indexed: 12/29/2022]
Abstract
To establish and maintain an ecological niche, bacteria employ a wide range of pathways to inhibit the growth of their microbial competitors. Some of these pathways, such as those that produce antibiotics or bacteriocins, exert toxicity on nearby cells in a cell contact-independent manner. More recently, however, several mechanisms of interbacterial antagonism requiring cell-to-cell contact have been identified. This form of microbial competition is mediated by antibacterial protein toxins whose delivery to target bacteria uses protein secretion apparatuses embedded within the cell envelope of toxin-producing bacteria. In this review, we discuss recent work implicating the bacterial Type I, IV, VI, and VII secretion systems in the export of antibacterial 'effector' proteins that mediate contact-dependent interbacterial antagonism.
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Affiliation(s)
- Timothy A Klein
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada L8S 4K1; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada L8S 4K1
| | - Shehryar Ahmad
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada L8S 4K1; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada L8S 4K1
| | - John C Whitney
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada L8S 4K1; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada L8S 4K1; David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, ON, Canada L8S 4K1.
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29
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Macori G, Bellio A, Bianchi DM, Chiesa F, Gallina S, Romano A, Zuccon F, Cabrera-Rubio R, Cauquil A, Merda D, Auvray F, Decastelli L. Genome-Wide Profiling of Enterotoxigenic Staphylococcus aureus Strains Used for the Production of Naturally Contaminated Cheeses. Genes (Basel) 2019; 11:E33. [PMID: 31892220 PMCID: PMC7016664 DOI: 10.3390/genes11010033] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2019] [Revised: 12/19/2019] [Accepted: 12/22/2019] [Indexed: 12/12/2022] Open
Abstract
Staphylococcus aureus is a major human pathogen and an important cause of livestock infections. More than 20 staphylococcal enterotoxins with emetic activity can be produced by specific strains responsible for staphylococcal food poisoning, one of the most common food-borne diseases. Whole genome sequencing provides a comprehensive view of the genome structure and gene content that have largely been applied in outbreak investigations and genomic comparisons. In this study, six enterotoxigenic S. aureus strains were characterised using a combination of molecular, phenotypical and computational methods. The genomes were analysed for the presence of virulence factors (VFs), where we identified 110 genes and classified them into five categories: adherence (n = 31), exoenzymes (n = 28), genes involved in host immune system evasion (n = 7); iron uptake regulatory system (n = 8); secretion machinery factors and toxins' genes (n = 36), and 39 genes coding for transcriptional regulators related to staphylococcal VFs. Each group of VFs revealed correlations among the six enterotoxigenic strains, and further analysis revealed their accessory genomic content, including mobile genetic elements. The plasmids pLUH02 and pSK67 were detected in the strain ProNaCC1 and ProNaCC7, respectively, carrying out the genes sed, ser, and selj. The genes carried out by prophages were detected in the strain ProNaCC2 (see), ProNaCC4, and ProNaCC7 (both positive for sea). The strain ProNaCC5 resulted positive for the genes seg, sei, sem, sen, seo grouped in an exotoxin gene cluster, and the strain ProNaCC6 resulted positive for seh, a transposon-associated gene. The six strains were used for the production of naturally contaminated cheeses which were tested with the European Screening Method for staphylococcal enterotoxins. The results obtained from the analysis of toxins produced in cheese, combined with the genomic features represent a portrait of the strains that can be used for the production of staphylococcal enterotoxin-positive cheese as reference material.
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Affiliation(s)
- Guerrino Macori
- National Reference Laboratory for Coagulase-Positive Staphylococci including Staphylococcus aureus, Istituto Zooprofilattico Sperimentale del Piemonte, Liguria e Valle d’Aosta, Via Bologna 148, 10154 Torino, Italy; (A.B.); (D.M.B.); (S.G.); (A.R.); (F.Z.); (L.D.)
| | - Alberto Bellio
- National Reference Laboratory for Coagulase-Positive Staphylococci including Staphylococcus aureus, Istituto Zooprofilattico Sperimentale del Piemonte, Liguria e Valle d’Aosta, Via Bologna 148, 10154 Torino, Italy; (A.B.); (D.M.B.); (S.G.); (A.R.); (F.Z.); (L.D.)
| | - Daniela Manila Bianchi
- National Reference Laboratory for Coagulase-Positive Staphylococci including Staphylococcus aureus, Istituto Zooprofilattico Sperimentale del Piemonte, Liguria e Valle d’Aosta, Via Bologna 148, 10154 Torino, Italy; (A.B.); (D.M.B.); (S.G.); (A.R.); (F.Z.); (L.D.)
| | - Francesco Chiesa
- Dipartimento di Scienze Veterinarie, Università di Torino, 10095 Grugliasco, Italy;
| | - Silvia Gallina
- National Reference Laboratory for Coagulase-Positive Staphylococci including Staphylococcus aureus, Istituto Zooprofilattico Sperimentale del Piemonte, Liguria e Valle d’Aosta, Via Bologna 148, 10154 Torino, Italy; (A.B.); (D.M.B.); (S.G.); (A.R.); (F.Z.); (L.D.)
| | - Angelo Romano
- National Reference Laboratory for Coagulase-Positive Staphylococci including Staphylococcus aureus, Istituto Zooprofilattico Sperimentale del Piemonte, Liguria e Valle d’Aosta, Via Bologna 148, 10154 Torino, Italy; (A.B.); (D.M.B.); (S.G.); (A.R.); (F.Z.); (L.D.)
| | - Fabio Zuccon
- National Reference Laboratory for Coagulase-Positive Staphylococci including Staphylococcus aureus, Istituto Zooprofilattico Sperimentale del Piemonte, Liguria e Valle d’Aosta, Via Bologna 148, 10154 Torino, Italy; (A.B.); (D.M.B.); (S.G.); (A.R.); (F.Z.); (L.D.)
| | - Raúl Cabrera-Rubio
- Teagasc Food Research Centre, Moorepark, Fermoy, P61 C996, Ireland-APC Microbiome Ireland, University College Cork, T12YT20 Cork, Ireland;
| | - Alexandra Cauquil
- European Laboratory for Coagulase-Positive Staphylococci including Staphylococcus aureus, Laboratory for Food Safety, ANSES, Université Paris-Est, F-94700 Maisons-Alfort, France; (A.C.); (D.M.); (F.A.)
| | - Déborah Merda
- European Laboratory for Coagulase-Positive Staphylococci including Staphylococcus aureus, Laboratory for Food Safety, ANSES, Université Paris-Est, F-94700 Maisons-Alfort, France; (A.C.); (D.M.); (F.A.)
| | - Fréderic Auvray
- European Laboratory for Coagulase-Positive Staphylococci including Staphylococcus aureus, Laboratory for Food Safety, ANSES, Université Paris-Est, F-94700 Maisons-Alfort, France; (A.C.); (D.M.); (F.A.)
| | - Lucia Decastelli
- National Reference Laboratory for Coagulase-Positive Staphylococci including Staphylococcus aureus, Istituto Zooprofilattico Sperimentale del Piemonte, Liguria e Valle d’Aosta, Via Bologna 148, 10154 Torino, Italy; (A.B.); (D.M.B.); (S.G.); (A.R.); (F.Z.); (L.D.)
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EssH Peptidoglycan Hydrolase Enables Staphylococcus aureus Type VII Secretion across the Bacterial Cell Wall Envelope. J Bacteriol 2018; 200:JB.00268-18. [PMID: 30082459 DOI: 10.1128/jb.00268-18] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 07/31/2018] [Indexed: 11/20/2022] Open
Abstract
The ESAT-6-like secretion system (ESS) of Staphylococcus aureus is assembled in the bacterial membrane from core components that promote the secretion of WXG-like proteins (EsxA, EsxB, EsxC, and EsxD) and the EssD effector. Genes encoding the ESS secretion machinery components, effector, and WXG-like proteins are located in the ess locus. Here, we identify essH, a heretofore uncharacterized gene of the ess locus, whose product is secreted via an N-terminal signal peptide into the extracellular medium of staphylococcal cultures. EssH exhibits two peptidoglycan hydrolase activities, cleaving the pentaglycine cross bridge and the amide bond of N-acetylmuramyl-l-alanine, thereby separating glycan chains and wall peptides with cleaved cross bridges. Unlike other peptidoglycan hydrolases, EssH does not promote the lysis of staphylococci. EssH residues Cys199 and His254, which are conserved in other CHAP domain enzymes, are required for peptidoglycan hydrolase activity and for S. aureus ESS secretion. These data suggest that EssH and its murein hydrolase activity are required for protein secretion by the ESS pathway.IMPORTANCE Gene clusters encoding WXG-like proteins and FtsK/SpoIIIE-like P loop ATPases in Firmicutes encode type 7b secretion systems (T7bSS) for the transport of select protein substrates. The Staphylococcus aureus T7bSS assembles in the bacterial membrane and promotes the secretion of WXG-like proteins and effectors. The mechanisms whereby staphylococci extend the T7SS across the bacterial cell wall envelope are not known. Here, we show that staphylococci secrete EssH to cleave their peptidoglycan, thereby enabling T7bSS transport of proteins across the bacterial cell wall envelope.
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Molecular Basis for Immunity Protein Recognition of a Type VII Secretion System Exported Antibacterial Toxin. J Mol Biol 2018; 430:4344-4358. [PMID: 30194969 PMCID: PMC6193138 DOI: 10.1016/j.jmb.2018.08.027] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 08/29/2018] [Accepted: 08/30/2018] [Indexed: 02/07/2023]
Abstract
Gram-positive bacteria deploy the type VII secretion system (T7SS) to facilitate interactions between eukaryotic and prokaryotic cells. In recent work, we identified the TelC protein from Streptococcus intermedius as a T7SS-exported lipid II phosphatase that mediates interbacterial competition. TelC exerts toxicity in the inner wall zone of Gram-positive bacteria; however, intercellular intoxication of sister cells does not occur because they express the TipC immunity protein. In the present study, we sought to characterize the molecular basis of self-protection by TipC. Using sub-cellular localization and protease protection assays, we show that TipC is a membrane protein with an N-terminal transmembrane segment and a C-terminal TelC-inhibitory domain that protrudes into the inner wall zone. The 1.9-Å X-ray crystal structure of a non-protective TipC paralogue reveals that the soluble domain of TipC proteins adopts a crescent-shaped fold that is composed of three α-helices and a seven-stranded β-sheet. Subsequent homology-guided mutagenesis demonstrates that a concave surface formed by the predicted β-sheet of TipC is required for both its interaction with TelC and its TelC-inhibitory activity. S. intermedius cells lacking the tipC gene are susceptible to growth inhibition by TelC delivered between cells; however, we find that the growth of this strain is unaffected by endogenous or overexpressed TelC, although the toxin accumulates in culture supernatants. Together, these data indicate that the TelC-inhibitory activity of TipC is only required for intercellularly transferred TelC and that the T7SS apparatus transports TelC across the cell envelope in a single step, bypassing the cellular compartment in which it exerts toxicity en route. Antibacterial TelC toxin is neutralized in the inner wall zone by membrane-anchored TipC immunity protein. TipC is a crescent-shaped protein that interacts with TelC via its concave surface. TelC and TipC are physically separated by the plasma membrane in TelC-producing cells. The type VII secretion system prevents TelC access to the inner wall zone in TelC-producing bacteria.
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Michalska K, Quan Nhan D, Willett JLE, Stols LM, Eschenfeldt WH, Jones AM, Nguyen JY, Koskiniemi S, Low DA, Goulding CW, Joachimiak A, Hayes CS. Functional plasticity of antibacterial EndoU toxins. Mol Microbiol 2018; 109:509-527. [PMID: 29923643 PMCID: PMC6173971 DOI: 10.1111/mmi.14007] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/15/2018] [Indexed: 01/05/2023]
Abstract
Bacteria use several different secretion systems to deliver toxic EndoU ribonucleases into neighboring cells. Here, we present the first structure of a prokaryotic EndoU toxin in complex with its cognate immunity protein. The contact-dependent growth inhibition toxin CdiA-CTSTECO31 from Escherichia coli STEC_O31 adopts the eukaryotic EndoU fold and shares greatest structural homology with the nuclease domain of coronavirus Nsp15. The toxin contains a canonical His-His-Lys catalytic triad in the same arrangement as eukaryotic EndoU domains, but lacks the uridylate-specific ribonuclease activity that characterizes the superfamily. Comparative sequence analysis indicates that bacterial EndoU domains segregate into at least three major clades based on structural variations in the N-terminal subdomain. Representative EndoU nucleases from clades I and II degrade tRNA molecules with little specificity. In contrast, CdiA-CTSTECO31 and other clade III toxins are specific anticodon nucleases that cleave tRNAGlu between nucleotides C37 and m2 A38. These findings suggest that the EndoU fold is a versatile scaffold for the evolution of novel substrate specificities. Such functional plasticity may account for the widespread use of EndoU effectors by diverse inter-bacterial toxin delivery systems.
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Affiliation(s)
- Karolina Michalska
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL, USA.,Structural Biology Center, Biosciences Division, Argonne National Laboratory, Argonne, IL, USA
| | - Dinh Quan Nhan
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Julia L E Willett
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Lucy M Stols
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL, USA
| | - William H Eschenfeldt
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL, USA
| | - Allison M Jones
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Josephine Y Nguyen
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Sanna Koskiniemi
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - David A Low
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA.,Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, USA
| | - Celia W Goulding
- Department of Molecular Biology & Biochemistry, University of California, Irvine, CA, USA.,Pharmaceutical Sciences, University of California, Irvine, CA, USA
| | - Andrzej Joachimiak
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL, USA.,Structural Biology Center, Biosciences Division, Argonne National Laboratory, Argonne, IL, USA.,Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA
| | - Christopher S Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA.,Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, USA
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The C-terminus of the ESAT6-like secretion system virulence factor EsxC mediates divalent cation-dependent homodimerization. Toxicon 2018; 146:129-137. [PMID: 29499245 DOI: 10.1016/j.toxicon.2018.02.047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 01/29/2018] [Accepted: 02/26/2018] [Indexed: 11/21/2022]
Abstract
The human pathogen Staphylococcus aureus encodes the ESAT6-like Secretion System (ESS). The ESS pathway secretes pathogenic substrates such as EsxA, EsxB, EsxC, EsxD and EssD that mediate staphylococcal establishment in persistent abscess lesions. The biochemical behavior of these substrates is not fully understood. EsxC is species-specific lysine-rich homodimer that lacks recognizable topogenic sequence. Studies have shown that EsxC is required for the secretion of other substrates, thereby revealing its biomedical importance. Here, EsxC self-association was investigated in the presence of several metal ion chelators. Results show that EsxC homodimerization is abolished in the presence of EDTA and EGTA, suggesting a role for calcium in mediating EsxC self-association. Complementation experiments confirm that EsxC homodimerization is calcium-dependent. N- and C-terminal truncations of EsxC were constructed, followed by bacterial two-hybrid screening. Results show that EsxC self-association is mediated by its C-terminal domain. Affinity purification of recombinant EsxC to apparent homogeneity, followed by chemical crosslinking and SDS-PAGE led to the detection of the monomeric and dimeric forms of the protein. In contrast and when a purified EsxC variant lacking the C-terminus was subjected to similar conditions, only the monomeric form was observed. These in vivo and in vitro data highlight the contribution of the C-terminus of the virulence factor EsxC to self-association, and document a previously unreported role for calcium in mediating protein-protein interactions in this pathogenic secretion system.
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Jamet A, Charbit A, Nassif X. Antibacterial Toxins: Gram-Positive Bacteria Strike Back! Trends Microbiol 2018; 26:89-91. [DOI: 10.1016/j.tim.2017.11.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 11/02/2017] [Accepted: 11/06/2017] [Indexed: 11/27/2022]
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Mielich-Süss B, Wagner RM, Mietrach N, Hertlein T, Marincola G, Ohlsen K, Geibel S, Lopez D. Flotillin scaffold activity contributes to type VII secretion system assembly in Staphylococcus aureus. PLoS Pathog 2017; 13:e1006728. [PMID: 29166667 PMCID: PMC5718613 DOI: 10.1371/journal.ppat.1006728] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 12/06/2017] [Accepted: 11/02/2017] [Indexed: 12/13/2022] Open
Abstract
Scaffold proteins are ubiquitous chaperones that promote efficient interactions between partners of multi-enzymatic protein complexes; although they are well studied in eukaryotes, their role in prokaryotic systems is poorly understood. Bacterial membranes have functional membrane microdomains (FMM), a structure homologous to eukaryotic lipid rafts. Similar to their eukaryotic counterparts, bacterial FMM harbor a scaffold protein termed flotillin that is thought to promote interactions between proteins spatially confined to the FMM. Here we used biochemical approaches to define the scaffold activity of the flotillin homolog FloA of the human pathogen Staphylococcus aureus, using assembly of interacting protein partners of the type VII secretion system (T7SS) as a case study. Staphylococcus aureus cells that lacked FloA showed reduced T7SS function, and thus reduced secretion of T7SS-related effectors, probably due to the supporting scaffold activity of flotillin. We found that the presence of flotillin mediates intermolecular interactions of T7SS proteins. We tested several small molecules that interfere with flotillin scaffold activity, which perturbed T7SS activity in vitro and in vivo. Our results suggest that flotillin assists in the assembly of S. aureus membrane components that participate in infection and influences the infective potential of this pathogen. The recently discovered functional membrane microdomains (FMM) of prokaryotic cells contain a protein homologous to the scaffold protein flotillin found in eukaryotic lipid rafts. It remains to be elucidated whether, like their eukaryotic counterparts, flotillin homolog proteins have a scaffold function in bacteria. Here we show that the Staphylococcus aureus flotillin FloA acts as a scaffold protein, to promote more efficient assembly of membrane-associated protein interacting partners of multi-enzyme complexes. In a case study, we provide biochemical evidence that FloA participates in assembly of the Type VII secretion system and thus contributes to S. aureus infective potential. Targeted dispersion of FMM-related processes using anti-FMM molecules opens up new perspectives for microbial therapies to treat persistent S. aureus infections.
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Affiliation(s)
- Benjamin Mielich-Süss
- Research Center for Infectious Diseases ZINF, University of Würzburg, Würzburg, Germany
- Institute for Molecular Infection Biology IMIB, University of Würzburg, Würzburg, Germany
| | - Rabea M. Wagner
- Research Center for Infectious Diseases ZINF, University of Würzburg, Würzburg, Germany
- Institute for Molecular Infection Biology IMIB, University of Würzburg, Würzburg, Germany
- National Center for Biotechnology, Consejo Superior de Investigaciones Científicas (CNB-CSIC), Madrid, Spain
| | - Nicole Mietrach
- Research Center for Infectious Diseases ZINF, University of Würzburg, Würzburg, Germany
- Institute for Molecular Infection Biology IMIB, University of Würzburg, Würzburg, Germany
- Rudolf Virchow Center - DFG Research Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany
| | - Tobias Hertlein
- Institute for Molecular Infection Biology IMIB, University of Würzburg, Würzburg, Germany
| | - Gabriella Marincola
- Research Center for Infectious Diseases ZINF, University of Würzburg, Würzburg, Germany
- Institute for Molecular Infection Biology IMIB, University of Würzburg, Würzburg, Germany
| | - Knut Ohlsen
- Institute for Molecular Infection Biology IMIB, University of Würzburg, Würzburg, Germany
| | - Sebastian Geibel
- Research Center for Infectious Diseases ZINF, University of Würzburg, Würzburg, Germany
- Institute for Molecular Infection Biology IMIB, University of Würzburg, Würzburg, Germany
- Rudolf Virchow Center - DFG Research Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany
| | - Daniel Lopez
- Research Center for Infectious Diseases ZINF, University of Würzburg, Würzburg, Germany
- Institute for Molecular Infection Biology IMIB, University of Würzburg, Würzburg, Germany
- National Center for Biotechnology, Consejo Superior de Investigaciones Científicas (CNB-CSIC), Madrid, Spain
- * E-mail:
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Cuthbert BJ, Burley KH, Goulding CW. Introducing the new bacterial branch of the RNase A superfamily. RNA Biol 2017; 15:9-12. [PMID: 29099294 DOI: 10.1080/15476286.2017.1387710] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Bovine pancreatic ribonuclease (RNase A) is the founding member of the RNase A superfamily. Members of this superfamily of ribonucleases have high sequence diversity, but possess a similar structural fold, together with a conserved His-Lys-His catalytic triad and structural disulfide bonds. Until recently, RNase A proteins had exclusively been identified in eukaryotes within vertebrae. Here, we discuss the discovery by Batot et al. of a bacterial RNase A superfamily member, CdiA-CTYkris: a toxin that belongs to an inter-bacterial competition system from Yersinia kristensenii. CdiA-CTYkris exhibits the same structural fold as conventional RNase A family members and displays in vitro and in vivo ribonuclease activity. However, CdiA-CTYkris shares little to no sequence similarity with RNase A, and lacks the conserved disulfide bonds and catalytic triad of RNase A. Interestingly, the CdiA-CTYkris active site more closely resembles the active site composition of various eukaryotic endonucleases. Despite lacking sequence similarity to eukaryotic RNase A family members, CdiA-CTYkris does share high sequence similarity with numerous Gram-negative and Gram-positive bacterial proteins/domains. Nearly all of these bacterial homologs are toxins associated with virulence and bacterial competition, suggesting that the RNase A superfamily has a distinct bacterial subfamily branch, which likely arose by way of convergent evolution. Finally, RNase A interacts directly with the immunity protein of CdiA-CTYkris, thus the cognate immunity protein for the bacterial RNase A member could be engineered as a new eukaryotic RNase A inhibitor.
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Affiliation(s)
- Bonnie J Cuthbert
- a Department of Molecular Biology and Biochemistry , University of California Irvine , Irvine , CA , USA
| | - Kalistyn H Burley
- b Department of Pharmaceutical Sciences , University of California Irvine , Irvine , CA , USA
| | - Celia W Goulding
- a Department of Molecular Biology and Biochemistry , University of California Irvine , Irvine , CA , USA.,b Department of Pharmaceutical Sciences , University of California Irvine , Irvine , CA , USA
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Isolation of a Membrane Protein Complex for Type VII Secretion in Staphylococcus aureus. J Bacteriol 2017; 199:JB.00482-17. [PMID: 28874412 DOI: 10.1128/jb.00482-17] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 08/29/2017] [Indexed: 11/20/2022] Open
Abstract
The ESAT6-like secretion system (ESS) of Staphylococcus aureus promotes effector protein transport across the bacterial envelope. Genes in the ESS cluster are required for S. aureus establishment of persistent abscess lesions and the modulation of immune responses during bloodstream infections. However, the biochemical functions of most of the ESS gene products, specifically the identity of secretion machine components, are unknown. Earlier work demonstrated that deletion of essB, which encodes a membrane protein, abolishes S. aureus ESS secretion. Loss-of-function mutations truncating the essB gene product cause dominant-negative phenotypes on ESS secretion, suggesting that EssB is a central component of the secretion machinery. To test this prediction, we purified native and affinity-tagged EssB from staphylococcal membranes via dodecyl-maltoside extraction, identifying a complex assembled from five proteins, EsaA, EssA, EssB, EssD, and EsxA. All five proteins are essential for secretion, as knockout mutations in the corresponding genes abolish ESS transport. Biochemical and bacterial two-hybrid analyses revealed a direct interaction between EssB and EsaA that, by engaging a mobile machine component, EsxA, may also recruit EssA and EssD.IMPORTANCE Type VII secretion systems support the lifestyle of Gram-positive bacteria, including important human pathogens such as Bacillus anthracis, Mycobacterium tuberculosis, and Staphylococcus aureus Genes encoding SpoIIIE-FtsK-like ATPases and WXG100-secreted products are conserved features of type VII secretion pathways; however, most of the genes in T7SS clusters are not conserved between different bacterial species. Here, we isolate a complex of proteins from the membranes of S. aureus that appears to represent the core secretion machinery, designated ESS. These results suggest that three membrane proteins, EsaA, EssB, and EssA, form a secretion complex that associates with EssC, the SpoIIIE-FtsK-like ATPase, and with EsxA, a mobile machine component and member of the WXG100 protein family.
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38
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Batot G, Michalska K, Ekberg G, Irimpan EM, Joachimiak G, Jedrzejczak R, Babnigg G, Hayes CS, Joachimiak A, Goulding CW. The CDI toxin of Yersinia kristensenii is a novel bacterial member of the RNase A superfamily. Nucleic Acids Res 2017; 45:5013-5025. [PMID: 28398546 PMCID: PMC5435912 DOI: 10.1093/nar/gkx230] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 03/31/2017] [Indexed: 01/01/2023] Open
Abstract
Contact-dependent growth inhibition (CDI) is an important mechanism of inter-bacterial competition found in many Gram-negative pathogens. CDI+ cells express cell-surface CdiA proteins that bind neighboring bacteria and deliver C-terminal toxin domains (CdiA-CT) to inhibit target-cell growth. CDI+ bacteria also produce CdiI immunity proteins, which specifically neutralize cognate CdiA-CT toxins to prevent self-inhibition. Here, we present the crystal structure of the CdiA-CT/CdiIYkris complex from Yersinia kristensenii ATCC 33638. CdiA-CTYkris adopts the same fold as angiogenin and other RNase A paralogs, but the toxin does not share sequence similarity with these nucleases and lacks the characteristic disulfide bonds of the superfamily. Consistent with the structural homology, CdiA-CTYkris has potent RNase activity in vitro and in vivo. Structure-guided mutagenesis reveals that His175, Arg186, Thr276 and Tyr278 contribute to CdiA-CTYkris activity, suggesting that these residues participate in substrate binding and/or catalysis. CdiIYkris binds directly over the putative active site and likely neutralizes toxicity by blocking access to RNA substrates. Significantly, CdiA-CTYkris is the first non-vertebrate protein found to possess the RNase A superfamily fold, and homologs of this toxin are associated with secretion systems in many Gram-negative and Gram-positive bacteria. These observations suggest that RNase A-like toxins are commonly deployed in inter-bacterial competition.
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Affiliation(s)
- Gaëlle Batot
- Department of Molecular Biology & Biochemistry, University of California Irvine, Irvine, CA 92697, USA
- These authors contributed equally to this work as first authors
| | - Karolina Michalska
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL 60439, USA
- Structural Biology Center, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
- These authors contributed equally to this work as first authors
| | - Greg Ekberg
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9625, USA
- These authors contributed equally to this work as first authors
| | - Ervin M. Irimpan
- Department of Molecular Biology & Biochemistry, University of California Irvine, Irvine, CA 92697, USA
| | - Grazyna Joachimiak
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Robert Jedrzejczak
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Gyorgy Babnigg
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Christopher S. Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9625, USA
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, Santa Barbara, CA 93106-9625, USA
| | - Andrzej Joachimiak
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL 60439, USA
- Structural Biology Center, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA
| | - Celia W. Goulding
- Department of Molecular Biology & Biochemistry, University of California Irvine, Irvine, CA 92697, USA
- Department of Pharmaceutical Sciences, University of California Irvine, Irvine, CA 92697, USA
- To whom correspondence should be addressed. Tel: +1 949 824 0337; Fax: +1 949 824 8551
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Cruciani M, Etna MP, Camilli R, Giacomini E, Percario ZA, Severa M, Sandini S, Rizzo F, Brandi V, Balsamo G, Polticelli F, Affabris E, Pantosti A, Bagnoli F, Coccia EM. Staphylococcus aureus Esx Factors Control Human Dendritic Cell Functions Conditioning Th1/Th17 Response. Front Cell Infect Microbiol 2017; 7:330. [PMID: 28785545 PMCID: PMC5519619 DOI: 10.3389/fcimb.2017.00330] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 07/05/2017] [Indexed: 02/01/2023] Open
Abstract
The opportunistic pathogen Staphylococcus aureus (S. aureus) is a major cause of nosocomial- and community-acquired infections. In addition, many antibiotic-resistant strains are emerging worldwide, thus, there is an urgent unmet need to pinpoint novel therapeutic and prophylactic strategies. In the present study, we characterized the impact of infection with the pandemic methicillin-resistant USA300 S. aureus strain on human primary dendritic cells (DC), key initiators and regulators of immune responses. In particular, among staphylococcal virulence factors, the function of EsxA and EsxB, two small acidic dimeric proteins secreted by the type VII-like secretion system Ess (ESAT-6-like secretion system), was investigated in human DC setting. A comparative analysis of bacterial entry, replication rate as well as DC maturation, apoptosis, signaling pathway activation and cytokine production was performed by using wild type (wt) USA300 and three isogenic mutants carrying the deletion of esxA (ΔesxA), esxB (ΔesxB), or both genes (ΔesxAB). The S. aureus mutant lacking only the EsxA protein (ΔesxA) stimulated a stronger pro-apoptotic phenotype in infected DC as compared to wt USA300, ΔesxAB, and ΔesxB strains. When the mutant carrying the esxB deletion (ΔesxB) was analyzed, a higher production of both regulatory and pro-inflammatory mediators was found in the infected DC with respect to those challenged with the wt counterpart and the other esx mutants. In accordance with these data, supernatant derived from ΔesxB-infected DC promoted a stronger release of both IFN-γ and IL-17 from CD4+ T cells as compared with those conditioned with supernatants derived from wild type USA300-, ΔesxAB-, and ΔesxA-infected cultures. Although, the interaction of S. aureus with human DC is not yet fully understood, our data suggest that both cytokine production and apoptotic process are modulated by Esx factors, thus indicating a possible role of these proteins in the modulation of DC-mediated immunity to S. aureus.
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Affiliation(s)
- Melania Cruciani
- Department of Science, University Roma TreRome, Italy.,Department of Infectious Diseases, Istituto Superiore di SanitàRome, Italy
| | - Marilena P Etna
- Department of Infectious Diseases, Istituto Superiore di SanitàRome, Italy
| | - Romina Camilli
- Department of Infectious Diseases, Istituto Superiore di SanitàRome, Italy
| | - Elena Giacomini
- Department of Infectious Diseases, Istituto Superiore di SanitàRome, Italy
| | | | - Martina Severa
- Department of Infectious Diseases, Istituto Superiore di SanitàRome, Italy
| | - Silvia Sandini
- Department of Infectious Diseases, Istituto Superiore di SanitàRome, Italy
| | - Fabiana Rizzo
- Department of Infectious Diseases, Istituto Superiore di SanitàRome, Italy
| | | | | | - Fabio Polticelli
- Department of Science, University Roma TreRome, Italy.,National Institute of Nuclear Physics, Roma Tre UniversityRome, Italy
| | | | - Annalisa Pantosti
- Department of Infectious Diseases, Istituto Superiore di SanitàRome, Italy
| | | | - Eliana M Coccia
- Department of Infectious Diseases, Istituto Superiore di SanitàRome, Italy
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Whitney JC, Peterson SB, Kim J, Pazos M, Verster AJ, Radey MC, Kulasekara HD, Ching MQ, Bullen NP, Bryant D, Goo YA, Surette MG, Borenstein E, Vollmer W, Mougous JD. A broadly distributed toxin family mediates contact-dependent antagonism between gram-positive bacteria. eLife 2017; 6. [PMID: 28696203 PMCID: PMC5555719 DOI: 10.7554/elife.26938] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 07/10/2017] [Indexed: 12/24/2022] Open
Abstract
The Firmicutes are a phylum of bacteria that dominate numerous polymicrobial habitats of importance to human health and industry. Although these communities are often densely colonized, a broadly distributed contact-dependent mechanism of interbacterial antagonism utilized by Firmicutes has not been elucidated. Here we show that proteins belonging to the LXG polymorphic toxin family present in Streptococcus intermedius mediate cell contact- and Esx secretion pathway-dependent growth inhibition of diverse Firmicute species. The structure of one such toxin revealed a previously unobserved protein fold that we demonstrate directs the degradation of a uniquely bacterial molecule required for cell wall biosynthesis, lipid II. Consistent with our functional data linking LXG toxins to interbacterial interactions in S. intermedius, we show that LXG genes are prevalent in the human gut microbiome, a polymicrobial community dominated by Firmicutes. We speculate that interbacterial antagonism mediated by LXG toxins plays a critical role in shaping Firmicute-rich bacterial communities. DOI:http://dx.doi.org/10.7554/eLife.26938.001 Most bacteria live in densely colonized environments, such as the human gut, in which they must constantly compete with other microbes for space and nutrients. As a result, bacteria have evolved a wide array of strategies to directly fight their neighbors. For example, some bacteria release antimicrobial compounds into their surroundings, while others ‘inject’ protein toxins directly into adjacent cells. Bacteria can be classified into two groups known as Gram-positive and Gram-negative. Previous studies found that Gram-negative bacteria inject toxins into neighboring cells, but no comparable toxins in Gram-positive bacteria had been identified. Before a bacterium can inject molecules into an adjacent cell, it needs to move the toxins from its interior to the cell surface. It had been suggested that a transport system in Gram-positive bacteria called the Esx pathway may export toxins known as LXG proteins. However, it was not clear whether these proteins help Gram-positive bacteria to compete against other bacteria. Whitney et al. studied the LXG proteins in Gram-positive bacteria known as Firmicutes. The experiments reveal that Firmicutes found in the human gut possess LXG genes. A Firmicute known as Streptococcus intermedius produces three LXG proteins that are all toxic to bacteria. To avoid being harmed by its own LXG proteins, S. intermedius also produces matching antidote proteins. Further experiments show that LXG proteins are exported out of S. intermedius cells and into adjacent competitor bacteria by the Esx pathway. Examining one of these LXG proteins in more detail showed that it can degrade a molecule that bacteria need to make their cell wall. Together, these findings suggest that LXG proteins may influence the species living in many important microbial communities, including the human gut. Changes in the communities of gut microbes have been linked with many diseases. Therefore, understanding more about how the LXG proteins work may help us to develop ways to manipulate these communities to improve human health. DOI:http://dx.doi.org/10.7554/eLife.26938.002
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Affiliation(s)
- John C Whitney
- Department of Microbiology, University of Washington School of Medicine, Seattle, United States
| | - S Brook Peterson
- Department of Microbiology, University of Washington School of Medicine, Seattle, United States
| | - Jungyun Kim
- Department of Microbiology, University of Washington School of Medicine, Seattle, United States
| | - Manuel Pazos
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle, United Kingdom
| | - Adrian J Verster
- Department of Genome Sciences, University of Washington, Seattle, United States
| | - Matthew C Radey
- Department of Microbiology, University of Washington School of Medicine, Seattle, United States
| | - Hemantha D Kulasekara
- Department of Microbiology, University of Washington School of Medicine, Seattle, United States
| | - Mary Q Ching
- Department of Microbiology, University of Washington School of Medicine, Seattle, United States
| | - Nathan P Bullen
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Canada.,Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Canada
| | - Diane Bryant
- Experimental Systems Group, Advanced Light Source, Berkeley, United States
| | - Young Ah Goo
- Northwestern Proteomics Core Facility, Northwestern University, Chicago, United States
| | - Michael G Surette
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Canada.,Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Canada.,Department of Medicine, Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, Canada
| | - Elhanan Borenstein
- Department of Genome Sciences, University of Washington, Seattle, United States.,Department of Computer Science and Engineering, University of Washington, Seattle, United States.,Santa Fe Institute, Santa Fe, United States
| | - Waldemar Vollmer
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle, United Kingdom
| | - Joseph D Mougous
- Department of Microbiology, University of Washington School of Medicine, Seattle, United States.,Howard Hughes Medical Institute, University of Washington School of Medicine, Seattle, United States
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41
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Dai Y, Wang Y, Liu Q, Gao Q, Lu H, Meng H, Qin J, Hu M, Li M. A Novel ESAT-6 Secretion System-Secreted Protein EsxX of Community-Associated Staphylococcus aureus Lineage ST398 Contributes to Immune Evasion and Virulence. Front Microbiol 2017; 8:819. [PMID: 28529509 PMCID: PMC5418362 DOI: 10.3389/fmicb.2017.00819] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 04/21/2017] [Indexed: 11/13/2022] Open
Abstract
The ESAT-6 secretion system (ESS) has been reported to contribute to the virulence and pathogenicity of several Staphylococcus aureus strains such as USA300 and Newman. However, the role of the ESS in community-associated S. aureus (CA-SA) lineage ST398 in China is not well understood. By comparing the ess locus of ST398 with the published S. aureus sequence in the NCBI database, we found one gene in the ess locus encoding a novel WXG superfamily protein that is highly conserved only in ST398. LC-MS/MS and Western blot analysis revealed that this protein is a novel secreted protein controlled by the ST398 ESS, and we named the protein EsxX. Although EsxX was not under the control of the accessory gene regulator like many other virulence factors and had no influence on several phenotypes of ST398, such as growth, hemolysis, and biofilm formation, it showed important impacts on immune evasion and virulence in ST398. An esxX deletion mutant led to significantly reduced resistance to neutrophil killing and decreased virulence in murine skin and blood infection models, indicating its essential contribution to the evasion of innate host defense and virulence to support the pathogenesis of ST398 infections. The function of this novel secreted protein EsxX might help us better understand the role of the ESS in the virulence and epidemic success of the CA-SA lineage ST398.
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Affiliation(s)
- Yingxin Dai
- Department of Laboratory Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong UniversityShanghai, China
| | - Yanan Wang
- Department of Laboratory Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong UniversityShanghai, China
| | - Qian Liu
- Department of Laboratory Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong UniversityShanghai, China
| | - Qianqian Gao
- Department of Laboratory Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong UniversityShanghai, China
| | - Huiying Lu
- Department of Laboratory Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong UniversityShanghai, China
| | - Hongwei Meng
- Department of Laboratory Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong UniversityShanghai, China
| | - Juanxiu Qin
- Department of Laboratory Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong UniversityShanghai, China
| | - Mo Hu
- Institute of Analytical Chemistry and Synthetic and Functional Biomolecules Center, College of Chemistry and Molecular Engineering, Peking UniversityBeijing, China
| | - Min Li
- Department of Laboratory Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong UniversityShanghai, China
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42
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EssE Promotes Staphylococcus aureus ESS-Dependent Protein Secretion To Modify Host Immune Responses during Infection. J Bacteriol 2016; 199:JB.00527-16. [PMID: 27795322 DOI: 10.1128/jb.00527-16] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 10/06/2016] [Indexed: 01/04/2023] Open
Abstract
Staphylococcus aureus, an invasive pathogen of humans and animals, requires a specialized ESS pathway to secrete proteins (EsxA, EsxB, EsxC, and EsxD) during infection. Expression of ess genes is required for S. aureus establishment of persistent abscess lesions following bloodstream infection; however, the mechanisms whereby effectors of the ESS pathway implement their virulence strategies were heretofore not known. Here, we show that EssE forms a complex with other members of the ESS secretion pathway and its substrates, promoting the secretion of EsxA, EsxB, EsxC, EsxD, and EssD. During bloodstream infection of mice, the S. aureus essE mutant displays defects in host cytokine responses, specifically in the production of interleukin-12 (IL-12) (p40/p70) and the suppression of RANTES (CCL5), activators of TH1 T cell responses and immune cell chemotaxis, respectively. Thus, essE-mediated secretion of protein effectors via the ESS pathway may enable S. aureus to manipulate host immune responses by modifying the production of cytokines. IMPORTANCE Staphylococcus aureus and other firmicutes evolved a specialized ESS (EsxA/ESAT-6-like secretion system) pathway for the secretion of small subsets of proteins lacking canonical signal peptides. The molecular mechanisms for ESS-dependent secretion and their functional purpose are still unknown. We demonstrate here that S. aureus EssE functions as a membrane assembly platform for elements of the secretion machinery and their substrates. Furthermore, S. aureus EssE-mediated secretion contributes to the production or the suppression of specific cytokines during host infection, thereby modifying immune responses toward this pathogen.
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