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Dufour D, Mankovskaia A, Chan Y, Motavaze K, Gong SG, Lévesque CM. A tripartite toxin-antitoxin module induced by quorum sensing is associated with the persistence phenotype in Streptococcus mutans. Mol Oral Microbiol 2018; 33:420-429. [PMID: 30298644 DOI: 10.1111/omi.12245] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 09/29/2018] [Accepted: 10/02/2018] [Indexed: 10/28/2022]
Abstract
The oral pathogen Streptococcus mutans communicates using a canonical Gram-positive quorum sensing system, CSP-ComDE. The CSP pheromone already known to be involved in the development of genetic competence positively influences the formation of persisters, dormant variants of regular cells that are highly tolerant to antimicrobial therapy. It is now believed that the persistence phenotype is the end result of a stochastic switch in the expression of toxin-antitoxin (TA) modules. TAs consist of a pair of genes that encode two components, a stable toxin and its cognate labile antitoxin. Transcription analyses revealed that three core genes encoding a putative TA system, called SmuATR, were members of the S. mutans CSP regulon. We hypothesized that S. mutans is using its CSP-ComDE system as a deterministic mechanism for persister formation through the activation of smuATR locus. We showed here that the SmuATR system constitutes a novel tripartite type II TA system in which the smuA and smuT genes encode an antitoxin and a toxin, respectively, while SmuR is a transcriptional repressor involved in the autoregulation of the operon. Ectopic expression of SmuA - SmuT is associated with the CSP-inducible persistence phenotype. In contrast, overexpression of SmuT alone is bactericidal and causes membrane permeabilization. To our knowledge, SmuATR is the first functional chromosomal tripartite TA system shown to be induced by the bacterial quorum sensing system and involved in persister formation.
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Affiliation(s)
- Delphine Dufour
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada
| | | | - Yuki Chan
- Department of Applied Oral Sciences, Faculty of Dentistry, The University of Hong Kong, Hong Kong, Hong Kong
| | - Kamyar Motavaze
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada
| | - Siew-Ging Gong
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada
| | - Céline M Lévesque
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada.,Department of Applied Oral Sciences, Faculty of Dentistry, The University of Hong Kong, Hong Kong, Hong Kong
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Grohmann E, Goessweiner-Mohr N, Brantl S. DNA-Binding Proteins Regulating pIP501 Transfer and Replication. Front Mol Biosci 2016; 3:42. [PMID: 27563645 PMCID: PMC4981023 DOI: 10.3389/fmolb.2016.00042] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 07/29/2016] [Indexed: 12/21/2022] Open
Abstract
pIP501 is a Gram-positive broad-host-range model plasmid intensively used for studying plasmid replication and conjugative transfer. It is a multiple antibiotic resistance plasmid frequently detected in clinical Enterococcus faecalis and Enterococcus faecium strains. Replication of pIP501 proceeds unidirectionally by a theta mechanism. The minimal replicon of pIP501 is composed of the repR gene encoding the essential rate-limiting replication initiator protein RepR and the origin of replication, oriR, located downstream of repR. RepR is similar to RepE of related streptococcal plasmid pAMβ1, which has been shown to possess RNase activity cleaving free RNA molecules in close proximity of the initiation site of DNA synthesis. Replication of pIP501 is controlled by the concerted action of a small protein, CopR, and an antisense RNA, RNAIII. CopR has a dual function: It acts as transcriptional repressor at the repR promoter and, in addition, prevents convergent transcription of RNAIII and repR mRNA (RNAII), which indirectly increases RNAIII synthesis. CopR binds asymmetrically as a dimer at two consecutive binding sites upstream of and overlapping with the repR promoter. RNAIII induces transcriptional attenuation within the leader region of the repR mRNA (RNAII). Deletion of either control component causes a 10- to 20-fold increase of plasmid copy number, while simultaneous deletions have no additional effect. Conjugative transfer of pIP501 depends on a type IV secretion system (T4SS) encoded in a single operon. Its transfer host-range is considerably broad, as it has been transferred to virtually all Gram-positive bacteria including Streptomyces and even the Gram-negative Escherichia coli. Expression of the 15 genes encoding the T4SS is tightly controlled by binding of the relaxase TraA, the transfer initiator protein, to the operon promoter overlapping with the origin of transfer (oriT). The T4SS operon encodes the DNA-binding proteins TraJ (VirD4-like coupling protein) and the VirB4-like ATPase, TraE. Both proteins are actively involved in conjugative DNA transport. Moreover, the operon encodes TraN, a small cytoplasmic protein, whose specific binding to a sequence upstream of the oriT nic-site was demonstrated. TraN seems to be an effective repressor of pIP501 transfer, as conjugative transfer rates were significantly increased in an E. faecalis pIP501ΔtraN mutant.
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Affiliation(s)
- Elisabeth Grohmann
- Division of Infectious Diseases, University Medical Center FreiburgFreiburg im Breisgau, Germany; Life Sciences and Technology, Beuth University of Applied Sciences BerlinBerlin, Germany
| | - Nikolaus Goessweiner-Mohr
- Center for Structural System Biology, University Medical Center Hamburg-EppendorfHamburg, Germany; Deutsches Elektronen-SynchrotronHamburg, Germany; Institute of Molecular Biotechnology, Austrian Academy of SciencesVienna, Austria; Research Institute of Molecular PathologyVienna, Austria
| | - Sabine Brantl
- Lehrstuhl für Genetik, Biologisch-Pharmazeutische Fakultät, AG Bakteriengenetik, Friedrich-Schiller-Universität Jena Jena, Germany
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Loh JMS, Proft T. Stabilized plasmid-based system for bioluminescent labeling of multiple streptococcal species. Biotechnol Lett 2015; 38:139-43. [PMID: 26410784 DOI: 10.1007/s10529-015-1967-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 09/22/2015] [Indexed: 10/23/2022]
Abstract
OBJECTIVE To determine if multiple streptococcal species can be easily labeled for biophotonic imaging using a toxin-antitoxin stabilized reporter plasmid containing the native firefly luciferase gene, originally developed for use in Group A Streptococcus. RESULTS A number of streptococcal species including Group B Streptococcus, Group C Streptococcus, Group G Streptococcus, S. iniae, S. vestibularis, and S. salivarius were successfully transformed with the reporter plasmid. In absence of antibiotic selection, the plasmid had variable stability amongst the six strains. The expression of firefly luciferase was highest in Group B Streptococcus and S. iniae, as observed by the brightest signal and lowest detection limits in vitro. CONCLUSION Multiple streptococcal species can be easily transformed with our toxin-antitoxin stabilized bioluminescent reporter plasmid. However, this plasmid shows variable stability and signal in different species, restricting its use for certain applications.
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Affiliation(s)
- Jacelyn M S Loh
- Department of Molecular Medicine & Pathology, School of Medical Sciences and the Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand.
| | - Thomas Proft
- Department of Molecular Medicine & Pathology, School of Medical Sciences and the Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand.
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Yao X, Chen T, Shen X, Zhao Y, Wang M, Rao X, Yin S, Wang J, Gong Y, Lu S, Le S, Tan Y, Tang J, Fuquan H, Li M. The chromosomal SezAT toxin-antitoxin system promotes the maintenance of the SsPI-1 pathogenicity island in epidemic Streptococcus suis. Mol Microbiol 2015; 98:243-57. [PMID: 26138696 DOI: 10.1111/mmi.13116] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/02/2015] [Indexed: 01/15/2023]
Abstract
Streptococcus suis has emerged as a causative agent of human meningitis and streptococcal toxic shock syndrome over the last years. The high pathogenicity of S. suis may be due in part to a laterally acquired pathogenicity island (renamed SsPI-1), which can spontaneously excise and transfer to recipients. Cells harboring excised SsPI-1 can potentially lose this island if cell division occurs prior to its reintegration; however, attempts to cure SsPI-1 from the host cells have been unsuccessful. Here, we report that an SsPI-1-borne Epsilon/Zeta toxin-antitoxin system (designated SezAT) promotes SsPI-1 stability in bacterial populations. The sezAT locus consists of two closely linked sezT and sezA genes encoding a toxin and its cognate antitoxin, respectively. Overproduction of SezT induces a bactericidal effect that can be neutralized by co-expression of SezA, but not by its later action. When devoid of a functional SezAT system, large-scale deletion of SsPI-1 is straightforward. Thus, SezAT serves to ensure inheritance of SsPI-1 during cell division, which may explain the persistence of epidemic S. suis. This report presents the first functional characterization of TA loci in S. suis, and the first biochemical evidence for the adaptive significance of the Epsilon/Zeta system in the evolution of pathogen virulence.
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Affiliation(s)
- Xinyue Yao
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Tian Chen
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Xiaodong Shen
- Department of Biochemistry and Molecular Biology, Third Military Medical University, Chongqing, 400038, China
| | - Yan Zhao
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Min Wang
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Xiancai Rao
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Supeng Yin
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Jing Wang
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Yali Gong
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Shuguang Lu
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Shuai Le
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Yinling Tan
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Jiaqi Tang
- PLA Research Institute of Clinical Laboratory Medicine, Nanjing General Hospital of Nanjing Military Command, Nanjing, 210002, China
| | - Hu Fuquan
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Ming Li
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
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Miller EW, Cao TN, Pflughoeft KJ, Sumby P. RNA-mediated regulation in Gram-positive pathogens: an overview punctuated with examples from the group A Streptococcus. Mol Microbiol 2014; 94:9-20. [PMID: 25091277 DOI: 10.1111/mmi.12742] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/31/2014] [Indexed: 11/29/2022]
Abstract
RNA-based mechanisms of regulation represent a ubiquitous class of regulators that are associated with diverse processes including nutrient sensing, stress response, modulation of horizontal gene transfer, and virulence factor expression. While better studied in Gram-negative bacteria, the literature is replete with examples of the importance of RNA-mediated regulatory mechanisms to the virulence and fitness of Gram-positives. Regulatory RNAs are classified as cis-acting, e.g. riboswitches, which modulate the transcription, translation, or stability of co-transcribed RNA, or trans-acting, e.g. small regulatory RNAs, which target separate mRNAs or proteins. The group A Streptococcus (GAS, Streptococcus pyogenes) is a Gram-positive bacterial pathogen from which several regulatory RNA mechanisms have been characterized. The study of RNA-mediated regulation in GAS has uncovered novel concepts with respect to how small regulatory RNAs may positively regulate target mRNA stability, and to how CRISPR RNAs are processed from longer precursors. This review provides an overview of RNA-mediated regulation in Gram-positive bacteria, and is highlighted with specific examples from GAS research. The key roles that these systems play in regulating bacterial virulence are discussed and future perspectives outlined.
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Affiliation(s)
- Eric W Miller
- Center for Molecular Medicine, Department of Microbiology & Immunology, University of Nevada, School of Medicine, Reno, NV, USA
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Brzozowska I, Zielenkiewicz U. The ClpXP protease is responsible for the degradation of the Epsilon antidote to the Zeta toxin of the streptococcal pSM19035 plasmid. J Biol Chem 2014; 289:7514-23. [PMID: 24492616 DOI: 10.1074/jbc.m113.519488] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Most bacterial genomes contain different types of toxin-antitoxin (TA) systems. The ω-ε-ζ proteinaceous type II TA cassette from the streptococcal pSM19035 plasmid is a member of the ε/ζ family, which is commonly found in multiresistance plasmids and chromosomes of various human pathogens. Regulation of type II TA systems relies on the proteolysis of antitoxin proteins. Under normal conditions, the Epsilon antidote neutralizes the Zeta toxin through the formation of a tight complex. In this study, we show, using both in vivo and in vitro analyses, that the ClpXP protease is responsible for Epsilon antitoxin degradation. Using in vivo studies, we examined the stability of the plasmids with active or inactive ω-ε-ζ TA cassettes in B. subtilis mutants that were defective for different proteases. Using in vitro assays, the degradation of purified His6-Epsilon by the His6-LonBs, ClpPBs, and ClpXBs proteases from B. subtilis was analyzed. Additionally, we showed that purified Zeta toxin protects the Epsilon protein from rapid ClpXP-catalyzed degradation.
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Affiliation(s)
- Iwona Brzozowska
- From the Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
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Regulation of toxin–antitoxin systems by proteolysis. Plasmid 2013; 70:33-41. [DOI: 10.1016/j.plasmid.2013.01.007] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 01/24/2013] [Accepted: 01/25/2013] [Indexed: 11/19/2022]
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Ma Z, Geng J, Yi L, Xu B, Jia R, Li Y, Meng Q, Fan H, Hu S. Insight into the specific virulence related genes and toxin-antitoxin virulent pathogenicity islands in swine streptococcosis pathogen Streptococcus equi ssp. zooepidemicus strain ATCC35246. BMC Genomics 2013; 14:377. [PMID: 23742619 PMCID: PMC3750634 DOI: 10.1186/1471-2164-14-377] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 05/28/2013] [Indexed: 01/10/2023] Open
Abstract
Background Streptococcus equi ssp. zooepidemicus (S. zooepidemicus) is an important pathogen causing swine streptococcosis in China. Pathogenicity islands (PAIs) of S. zooepidemicus have been transferred among bacteria through horizontal gene transfer (HGT) and play important roles in the adaptation and increased virulence of S. zooepidemicus. The present study used comparative genomics to examine the different pathogenicities of S. zooepidemicus. Results Genome of S. zooepidemicus ATCC35246 (Sz35246) comprises 2,167,264-bp of a single circular chromosome, with a GC content of 41.65%. Comparative genome analysis of Sz35246, S. zooepidemicus MGCS10565 (Sz10565), Streptococcus equi. ssp. equi. 4047 (Se4047) and S. zooepidemicus H70 (Sz70) identified 320 Sz35246-specific genes, clustered into three toxin-antitoxin (TA) systems PAIs and one restriction modification system (RM system) PAI. These four acquired PAIs encode proteins that may contribute to the overall pathogenic capacity and fitness of this bacterium to adapt to different hosts. Analysis of the in vivo and in vitro transcriptomes of this bacterium revealed differentially expressed PAI genes and non-PAI genes, suggesting that Sz35246 possess mechanisms for infecting animals and adapting to a wide range of host environments. Analysis of the genome identified potential Sz35246 virulence genes. Genes of the Fim III operon were presumed to be involved in breaking the host-restriction of Sz35246. Conclusion Genome wide comparisons of Sz35246 with three other strains and transcriptome analysis revealed novel genes related to bacterial virulence and breaking the host-restriction. Four specific PAIs, which were judged to have been transferred into Sz35246 genome through HGT, were identified for the first time. Further analysis of the TA and RM systems in the PAIs will improve our understanding of the pathogenicity of this bacterium and could lead to the development of diagnostics and vaccines.
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Affiliation(s)
- Zhe Ma
- College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, People's Republic of China
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