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Horstmann N, Myers KS, Tran CN, Flores AR, Shelburne III SA. CovS inactivation reduces CovR promoter binding at diverse virulence factor encoding genes in group A Streptococcus. PLoS Pathog 2022; 18:e1010341. [PMID: 35180278 PMCID: PMC8893699 DOI: 10.1371/journal.ppat.1010341] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 03/03/2022] [Accepted: 02/04/2022] [Indexed: 11/18/2022] Open
Abstract
The control of virulence gene regulator (CovR), also called caspsule synthesis regulator (CsrR), is critical to how the major human pathogen group A Streptococcus fine-tunes virulence factor production. CovR phosphorylation (CovR~P) levels are determined by its cognate sensor kinase CovS, and functional abrogating mutations in CovS can occur in invasive GAS isolates leading to hypervirulence. Presently, the mechanism of CovR-DNA binding specificity is unclear, and the impact of CovS inactivation on global CovR binding has not been assessed. Thus, we performed CovR chromatin immunoprecipitation sequencing (ChIP-seq) analysis in the emm1 strain MGAS2221 and its CovS kinase deficient derivative strain 2221-CovS-E281A. We identified that CovR bound in the promoter regions of nearly all virulence factor encoding genes in the CovR regulon. Additionally, direct CovR binding was observed for numerous genes encoding proteins involved in amino acid metabolism, but we found limited direct CovR binding to genes encoding other transcriptional regulators. The consensus sequence AATRANAAAARVABTAAA was present in the promoters of genes directly regulated by CovR, and mutations of highly conserved positions within this motif relieved CovR repression of the hasA and MGAS2221_0187 promoters. Analysis of strain 2221-CovS-E281A revealed that binding of CovR at repressed, but not activated, promoters is highly dependent on CovR~P state. CovR repressed virulence factor encoding genes could be grouped dependent on how CovR~P dependent variation in DNA binding correlated with gene transcript levels. Taken together, the data show that CovR repression of virulence factor encoding genes is primarily direct in nature, involves binding to a newly-identified DNA binding motif, and is relieved by CovS inactivation. These data provide new mechanistic insights into one of the most important bacterial virulence regulators and allow for subsequent focused investigations into how CovR-DNA interaction at directly controlled promoters impacts GAS pathogenesis. Tight regulation of virulence factor production is a critical, but poorly understood aspect of bacterial pathogenesis. The OmpR/PhoB family member control of virulence regulator (CovR) is the master virulence factor controller in group A Streptococcus (GAS), a bacterium which commonly causes a diverse array of human infections. Mutations in the cognate kinase of CovR, CovS, are commonly observed among invasive GAS isolates, but the functional impact of CovS on global CovR function is unknown. Herein, we defined CovR global DNA binding locations, identified a consensus CovR binding motif, and determined how inactivation of the CovR cognate sensor kinase, CovS, impacts CovR-DNA interaction. Our findings show that CovR-repressed virulence factor encoding genes are directly regulated by CovR and that CovS inactivation markedly reduces CovR binding at CovR-repressed promoters. Given the widespread nature of CovR homologues in streptococci and other Gram-positive pathogens, these findings extend understanding of mechanisms by which OmpR/PhoB family members impact the ability of bacteria to cause serious infections.
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Affiliation(s)
- Nicola Horstmann
- Department of Infectious Diseases, Infection Control and Employee Health, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
| | - Kevin S. Myers
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Chau Nguyen Tran
- Department of Infectious Diseases, Infection Control and Employee Health, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
| | - Anthony R. Flores
- Center for Antimicrobial Resistance and Microbial Genomics McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, United States of America
- Department of Pediatrics, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, United States of America
| | - Samuel A. Shelburne III
- Department of Infectious Diseases, Infection Control and Employee Health, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
- Department of Genomic Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
- * E-mail:
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Di Giacomo S, Toussaint F, Ledesma-García L, Knoops A, Vande Capelle F, Fremaux C, Horvath P, Ladrière JM, Ait-Abderrahim H, Hols P, Mignolet J. OUP accepted manuscript. FEMS Microbiol Rev 2022; 46:6543703. [PMID: 35254446 PMCID: PMC9300618 DOI: 10.1093/femsre/fuac014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 02/14/2022] [Accepted: 03/01/2022] [Indexed: 11/14/2022] Open
Abstract
Nowadays, the growing human population exacerbates the need for sustainable resources. Inspiration and achievements in nutrient production or human/animal health might emanate from microorganisms and their adaptive strategies. Here, we exemplify the benefits of lactic acid bacteria (LAB) for numerous biotechnological applications and showcase their natural transformability as a fast and robust method to hereditarily influence their phenotype/traits in fundamental and applied research contexts. We described the biogenesis of the transformation machinery and we analyzed the genome of hundreds of LAB strains exploitable for human needs to predict their transformation capabilities. Finally, we provide a stepwise rational path to stimulate and optimize natural transformation with standard and synthetic biology techniques. A comprehensive understanding of the molecular mechanisms driving natural transformation will facilitate and accelerate the improvement of bacteria with properties that serve broad societal interests.
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Affiliation(s)
- Stefano Di Giacomo
- Biochemistry and Genetics of Microorganisms (BGM), Louvain Institute of Biomolecular Science and Technology, Université catholique de Louvain, Croix du Sud 4-5, (box L7.07.06), B-1348 Louvain-la-Neuve, Belgium
| | - Frédéric Toussaint
- Biochemistry and Genetics of Microorganisms (BGM), Louvain Institute of Biomolecular Science and Technology, Université catholique de Louvain, Croix du Sud 4-5, (box L7.07.06), B-1348 Louvain-la-Neuve, Belgium
| | - Laura Ledesma-García
- Biochemistry and Genetics of Microorganisms (BGM), Louvain Institute of Biomolecular Science and Technology, Université catholique de Louvain, Croix du Sud 4-5, (box L7.07.06), B-1348 Louvain-la-Neuve, Belgium
| | - Adrien Knoops
- Biochemistry and Genetics of Microorganisms (BGM), Louvain Institute of Biomolecular Science and Technology, Université catholique de Louvain, Croix du Sud 4-5, (box L7.07.06), B-1348 Louvain-la-Neuve, Belgium
| | - Florence Vande Capelle
- Biochemistry and Genetics of Microorganisms (BGM), Louvain Institute of Biomolecular Science and Technology, Université catholique de Louvain, Croix du Sud 4-5, (box L7.07.06), B-1348 Louvain-la-Neuve, Belgium
| | - Christophe Fremaux
- Health and Biosciences, IFF Danisco France SAS, CS 10010, F-86220 Dangé-Saint-Romain, France
| | - Philippe Horvath
- Health and Biosciences, IFF Danisco France SAS, CS 10010, F-86220 Dangé-Saint-Romain, France
| | - Jean-Marc Ladrière
- Health and Biosciences, IFF Danisco France SAS, CS 10010, F-86220 Dangé-Saint-Romain, France
| | | | - Pascal Hols
- Corresponding author: Biochemistry and Genetics of Microorganisms, Louvain Institute of Biomolecular Science and Technology, Université catholique de Louvain, Croix du Sud 4-5 (box L7.07.06), B-1348 Louvain-La-Neuve, Belgium. Tel: +3210478896; Fax: +3210472825; E-mail:
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3
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Buckley SJ, Harvey RJ, Shan Z. Application of the random forest algorithm to Streptococcus pyogenes response regulator allele variation: from machine learning to evolutionary models. Sci Rep 2021; 11:12687. [PMID: 34135390 PMCID: PMC8209152 DOI: 10.1038/s41598-021-91941-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 05/27/2021] [Indexed: 02/07/2023] Open
Abstract
Group A Streptococcus (GAS) is a globally significant bacterial pathogen. The GAS genotyping gold standard characterises the nucleotide variation of emm, which encodes a surface-exposed protein that is recombinogenic and under immune-based selection pressure. Within a supervised learning methodology, we tested three random forest (RF) algorithms (Guided, Ordinary, and Regularized) and 53 GAS response regulator (RR) allele types to infer six genomic traits (emm-type, emm-subtype, tissue and country of sample, clinical outcomes, and isolate invasiveness). The Guided, Ordinary, and Regularized RF classifiers inferred the emm-type with accuracies of 96.7%, 95.7%, and 95.2%, using ten, three, and four RR alleles in the feature set, respectively. Notably, we inferred the emm-type with 93.7% accuracy using only mga2 and lrp. We demonstrated a utility for inferring emm-subtype (89.9%), country (88.6%), invasiveness (84.7%), but not clinical (56.9%), or tissue (56.4%), which is consistent with the complexity of GAS pathophysiology. We identified a novel cell wall-spanning domain (SF5), and proposed evolutionary pathways depicting the 'contrariwise' and 'likewise' chimeric deletion-fusion of emm and enn. We identified an intermediate strain, which provides evidence of the time-dependent excision of mga regulon genes. Overall, our workflow advances the understanding of the GAS mga regulon and its plasticity.
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Affiliation(s)
- Sean J Buckley
- School of Health and Behavioural Sciences, University of the Sunshine Coast, Locked Bag 4, Maroochydore DC, QLD, 4558, Australia.
| | - Robert J Harvey
- School of Health and Behavioural Sciences, University of the Sunshine Coast, Locked Bag 4, Maroochydore DC, QLD, 4558, Australia
- Sunshine Coast Health Institute, Birtinya, QLD, 4575, Australia
| | - Zack Shan
- Thompson Institute, University of the Sunshine Coast, Birtinya, QLD, 4575, Australia
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4
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Kunthavai PC, Kannan M, Ragunathan P. Structural analysis of alternate sigma factor ComX with RpoC, RpoB and its cognate CIN promoter reveals a distinctive promoter melting mechanism. J Biomol Struct Dyn 2021; 40:6272-6285. [PMID: 33554755 DOI: 10.1080/07391102.2021.1882338] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Alternate sigma factors play a major role in the survival of pathogenic bacteria such as Streptococcus pyogenes in adverse environment conditions. Stress induced sigma factors mediate gene expression under conditions of pathogenesis, dormancy and unusual environmental cues. In the present work, ComX, an alternate sigma factor from S. pyogenes has been characterized. The structures of ComX, RpoB β subunit and RpoC β' subunit of RNA polymerase have been predicted using comparative and homology modelling respectively and validated. Attempts have been made to study RpoB-RpoC-ComX complex interactions with Double Strand (DS) and Single Strand (SS) promoter regions. Stability of these complexes and the promoter melting mechanism have been analysed using Molecular Dynamic (MD) simulations. This study suggests that ComX, although identifies promoter analogous to the alternate sigma factor SigH of M. tuberculosis, follows a distinctive promoter flip out mechanism.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- P C Kunthavai
- Centre of Advanced study in Crystallography and Biophysics, University of Madras, Chennai, India
| | - Muthu Kannan
- Department of Biological sciences, National University of Singapore, Singapore, Singapore
| | - Preethi Ragunathan
- Centre of Advanced study in Crystallography and Biophysics, University of Madras, Chennai, India
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5
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Buckley SJ, Davies MR, McMillan DJ. In silico characterisation of stand-alone response regulators of Streptococcus pyogenes. PLoS One 2020; 15:e0240834. [PMID: 33075055 PMCID: PMC7571705 DOI: 10.1371/journal.pone.0240834] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 10/02/2020] [Indexed: 12/20/2022] Open
Abstract
Bacterial “stand-alone” response regulators (RRs) are pivotal to the control of gene transcription in response to changing cytosolic and extracellular microenvironments during infection. The genome of group A Streptococcus (GAS) encodes more than 30 stand-alone RRs that orchestrate the expression of virulence factors involved in infecting multiple tissues, so causing an array of potentially lethal human diseases. Here, we analysed the molecular epidemiology and biological associations in the coding sequences (CDSs) and upstream intergenic regions (IGRs) of 35 stand-alone RRs from a collection of global GAS genomes. Of the 944 genomes analysed, 97% encoded 32 or more of the 35 tested RRs. The length of RR CDSs ranged from 297 to 1587 nucleotides with an average nucleotide diversity (π) of 0.012, while the IGRs ranged from 51 to 666 nucleotides with average π of 0.017. We present new evidence of recombination in multiple RRs including mga, leading to mga-2 switching, emm-switching and emm-like gene chimerization, and the first instance of an isolate that encodes both mga-1 and mga-2. Recombination was also evident in rofA/nra and msmR loci with 15 emm-types represented in multiple FCT (fibronectin-binding, collagen-binding, T-antigen)-types, including novel emm-type/FCT-type pairings. Strong associations were observed between concatenated RR allele types, and emm-type, MLST-type, core genome phylogroup, and country of sampling. No strong associations were observed between individual loci and disease outcome. We propose that 11 RRs may form part of future refinement of GAS typing systems that reflect core genome evolutionary associations. This subgenomic analysis revealed allelic traits that were informative to the biological function, GAS strain definition, and regional outbreak detection.
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Affiliation(s)
- Sean J. Buckley
- School of Health and Sports Sciences, University of the Sunshine Coast, Sippy Downs, Queensland, Australia
- * E-mail:
| | - Mark R. Davies
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
| | - David J. McMillan
- School of Health and Sports Sciences, University of the Sunshine Coast, Sippy Downs, Queensland, Australia
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6
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Roobthaisong A, Aikawa C, Nozawa T, Maruyama F, Nakagawa I. YvqE and CovRS of Group A Streptococcus Play a Pivotal Role in Viability and Phenotypic Adaptations to Multiple Environmental Stresses. PLoS One 2017; 12:e0170612. [PMID: 28122066 PMCID: PMC5266302 DOI: 10.1371/journal.pone.0170612] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 01/06/2017] [Indexed: 01/14/2023] Open
Abstract
Streptococcus pyogenes (group A Streptococcus, or GAS) is a human pathogen that causes a wide range of diseases. For successful colonization within a variety of host niches, GAS utilizes TCSs to sense and respond to environmental changes and adapts its pathogenic traits accordingly; however, many GAS TCSs and their interactions remain uncharacterized. Here, we elucidated the roles of a poorly characterized TCS, YvqEC, and a well-studied TCS, CovRS, in 2 different GAS strain SSI-1 and JRS4, respectively. Deletion of yvqE and yvqC in JRS4 resulted in lower cell viability and abnormality of cell division when compared to the wild-type strain under standard culture conditions, demonstrating an important role for YvqEC. Furthermore, a double-deletion of yvqEC and covRS in SSI-1 and JRS4 resulted in a significantly impaired ability to survive under various stress conditions, as well as an increased sensitivity to cell wall-targeting antibiotics compared to that observed in either single mutant or wild-type strains suggesting synergistic interactions. Our findings provide new insights into the impact of poorly characterized TCS (YvqEC) and potential synergistic interactions between YvqEC and CovRS and reveal their potential role as novel therapeutic targets against GAS infection.
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Affiliation(s)
- Amonrattana Roobthaisong
- Section of Molecular Craniofacial Embryology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
- Department of Microbiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Chihiro Aikawa
- Department of Microbiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Takashi Nozawa
- Department of Microbiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Fumito Maruyama
- Department of Microbiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Ichiro Nakagawa
- Department of Microbiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- * E-mail:
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7
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Ibrahim J, Eisen JA, Jospin G, Coil DA, Khazen G, Tokajian S. Genome Analysis of Streptococcus pyogenes Associated with Pharyngitis and Skin Infections. PLoS One 2016; 11:e0168177. [PMID: 27977735 PMCID: PMC5158041 DOI: 10.1371/journal.pone.0168177] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 11/25/2016] [Indexed: 12/12/2022] Open
Abstract
Streptococcus pyogenes is a very important human pathogen, commonly associated with skin or throat infections but can also cause life-threatening situations including sepsis, streptococcal toxic shock syndrome, and necrotizing fasciitis. Various studies involving typing and molecular characterization of S. pyogenes have been published to date; however next-generation sequencing (NGS) studies provide a comprehensive collection of an organism’s genetic variation. In this study, the genomes of nine S. pyogenes isolates associated with pharyngitis and skin infection were sequenced and studied for the presence of virulence genes, resistance elements, prophages, genomic recombination, and other genomic features. Additionally, a comparative phylogenetic analysis of the isolates with global clones highlighted their possible evolutionary lineage and their site of infection. The genomes were found to also house a multitude of features including gene regulation systems, virulence factors and antimicrobial resistance mechanisms.
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Affiliation(s)
- Joe Ibrahim
- Department of Natural Sciences, Lebanese American University, School of Arts and Sciences, Byblos, Lebanon
| | - Jonathan A. Eisen
- University of California Davis Genome Center, Davis, California, United States of America
| | - Guillaume Jospin
- University of California Davis Genome Center, Davis, California, United States of America
| | - David A. Coil
- University of California Davis Genome Center, Davis, California, United States of America
| | - Georges Khazen
- Department of Computer Science and Mathematics, Lebanese American University, School of Arts and Sciences, Byblos, Lebanon
| | - Sima Tokajian
- Department of Natural Sciences, Lebanese American University, School of Arts and Sciences, Byblos, Lebanon
- * E-mail:
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8
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Fontaine L, Wahl A, Fléchard M, Mignolet J, Hols P. Regulation of competence for natural transformation in streptococci. INFECTION GENETICS AND EVOLUTION 2015; 33:343-60. [DOI: 10.1016/j.meegid.2014.09.010] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2014] [Revised: 08/28/2014] [Accepted: 09/07/2014] [Indexed: 02/02/2023]
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9
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Transcription of the Streptococcus pyogenes hyaluronic acid capsule biosynthesis operon is regulated by previously unknown upstream elements. Infect Immun 2014; 82:5293-307. [PMID: 25287924 DOI: 10.1128/iai.02035-14] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The important human pathogen Streptococcus pyogenes (group A Streptococcus [GAS]) produces a hyaluronic acid (HA) capsule that plays critical roles in immune evasion. Previous studies showed that the hasABC operon encoding the capsule biosynthesis enzymes is under the control of a single promoter, P1, which is negatively regulated by the two-component regulatory system CovR/S. In this work, we characterize the sequence upstream of P1 and identify a novel regulatory region controlling transcription of the capsule biosynthesis operon in the M1 serotype strain MGAS2221. This region consists of a promoter, P2, which initiates transcription of a novel small RNA, HasS, an intrinsic transcriptional terminator that inefficiently terminates HasS, permitting read-through transcription of hasABC, and a putative promoter which lies upstream of P2. Electrophoretic mobility shift assays, quantitative reverse transcription-PCR, and transcriptional reporter data identified CovR as a negative regulator of P2. We found that the P1 and P2 promoters are completely repressed by CovR, and capsule expression is regulated by the putative promoter upstream of P2. Deletion of hasS or of the terminator eliminates CovR-binding sequences, relieving repression and increasing read-through, hasA transcription, and capsule production. Sequence analysis of 44 GAS genomes revealed a high level of polymorphism in the HasS sequence region. Most of the HasS variations were located in the terminator sequences, suggesting that this region is under strong selective pressure. We discovered that the terminator deletion mutant is highly resistant to neutrophil-mediated killing and is significantly more virulent in a mouse model of GAS invasive disease than the wild-type strain. Together, these results are consistent with the naturally occurring mutations in this region modulating GAS virulence.
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10
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Johnston C, Martin B, Fichant G, Polard P, Claverys JP. Bacterial transformation: distribution, shared mechanisms and divergent control. Nat Rev Microbiol 2014; 12:181-96. [DOI: 10.1038/nrmicro3199] [Citation(s) in RCA: 402] [Impact Index Per Article: 40.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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11
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Gera K, McIver KS. Laboratory growth and maintenance of Streptococcus pyogenes (the Group A Streptococcus, GAS). ACTA ACUST UNITED AC 2013; 30:9D.2.1-9D.2.13. [PMID: 24510893 DOI: 10.1002/9780471729259.mc09d02s30] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Streptococcus pyogenes is a Gram-positive bacterium that strictly infects humans. It is the causative agent of a broad spectrum of diseases accounting for millions of infections and at least 517,000 deaths each year worldwide. It is a nutritionally fastidious organism that ferments sugars to produce lactic acid and has strict requirements for growth. To aid in the study of this organism, this unit describes the growth and maintenance of S. pyogenes.
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Affiliation(s)
- Kanika Gera
- Department of Cell Biology and Molecular Genetics, Maryland Pathogen Research Institute, University of Maryland, College Park, Maryland
| | - Kevin S McIver
- Department of Cell Biology and Molecular Genetics, Maryland Pathogen Research Institute, University of Maryland, College Park, Maryland
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12
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Hondorp ER, Hou SC, Hause LL, Gera K, Lee CE, McIver KS. PTS phosphorylation of Mga modulates regulon expression and virulence in the group A streptococcus. Mol Microbiol 2013; 88:1176-93. [PMID: 23651410 DOI: 10.1111/mmi.12250] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/29/2013] [Indexed: 10/26/2022]
Abstract
The ability of a bacterial pathogen to monitor available carbon sources in host tissues provides a clear fitness advantage. In the group A streptococcus (GAS), the virulence regulator Mga contains homology to phosphotransferase system (PTS) regulatory domains (PRDs) found in sugar operon regulators. Here we show that Mga was phosphorylated in vitro by the PTS components EI/HPr at conserved PRD histidines. A ΔptsI (EI-deficient) GAS mutant exhibited decreased Mga activity. However, PTS-mediated phosphorylation inhibited Mga-dependent transcription of emm in vitro. Using alanine (unphosphorylated) and aspartate (phosphomimetic) mutations of PRD histidines, we establish that a doubly phosphorylated PRD1 phosphomimetic (D/DMga4) is completely inactive in vivo, shutting down expression of the Mga regulon. Although D/DMga4 is still able to bind DNA in vitro, homo-multimerization of Mga is disrupted and the protein is unable to activate transcription. PTS-mediated regulation of Mga activity appears to be important for pathogenesis, as bacteria expressing either non-phosphorylated (A/A) or phosphomimetic (D/D) PRD1 Mga mutants were attenuated in a model of GAS invasive skin disease. Thus, PTS-mediated phosphorylation of Mga may allow the bacteria to modulate virulence gene expression in response to carbohydrate status. Furthermore, PRD-containing virulence regulators (PCVRs) appear to be widespread in Gram-positive pathogens.
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Affiliation(s)
- Elise R Hondorp
- Department of Cell Biology & Molecular Genetics and Maryland Pathogen Research Institute, University of Maryland, College Park, MD 20742, USA
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13
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The cryptic competence pathway in Streptococcus pyogenes is controlled by a peptide pheromone. J Bacteriol 2012; 194:4589-600. [PMID: 22730123 DOI: 10.1128/jb.00830-12] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Horizontal gene transfer is an important means of bacterial evolution that is facilitated by transduction, conjugation, and natural genetic transformation. Transformation occurs after bacterial cells enter a state of competence, where naked DNA is acquired from the extracellular environment. Induction of the competent state relies on signals that activate master regulators, causing the expression of genes involved in DNA uptake, processing, and recombination. All streptococcal species contain the master regulator SigX and SigX-dependent effector genes required for natural genetic transformation; however, not all streptococcal species have been shown to be naturally competent. We recently demonstrated that competence development in Streptococcus mutans requires the type II ComRS quorum-sensing circuit, comprising an Rgg transcriptional activator and a novel peptide pheromone (L. Mashburn-Warren, D. A. Morrison, and M. J. Federle, Mol. Microbiol. 78:589-606, 2010). The type II ComRS system is shared by the pyogenic, mutans, and bovis streptococci, including the clinically relevant pathogen Streptococcus pyogenes. Here, we describe the activation of sigX by a small-peptide pheromone and an Rgg regulator of the type II ComRS class. We confirm previous reports that SigX is functional and able to activate sigX-dependent gene expression within the competence regulon, and that SigX stability is influenced by the cytoplasmic protease ClpP. Genomic analyses of available S. pyogenes genomes revealed the presence of intact genes within the competence regulon. While this is the first report to show natural induction of sigX, S. pyogenes remained nontransformable under laboratory conditions. Using radiolabeled DNA, we demonstrate that transformation is blocked at the stage of DNA uptake.
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Egan SA, Ward PN, Watson M, Field TR, Leigh JA. Vru (Sub0144) controls expression of proven and putative virulence determinants and alters the ability of Streptococcus uberis to cause disease in dairy cattle. MICROBIOLOGY-SGM 2012; 158:1581-1592. [PMID: 22383474 PMCID: PMC3541772 DOI: 10.1099/mic.0.055863-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The regulation and control of gene expression in response to differing environmental stimuli is crucial for successful pathogen adaptation and persistence. The regulatory gene vru of Streptococcus uberis encodes a stand-alone response regulator with similarity to the Mga of group A Streptococcus. Mga controls expression of a number of important virulence determinants. Experimental intramammary challenge of dairy cattle with a mutant of S. uberis carrying an inactivating lesion in vru showed reduced ability to colonize the mammary gland and an inability to induce clinical signs of mastitis compared with the wild-type strain. Analysis of transcriptional differences of gene expression in the mutant, determined by microarray analysis, identified a number of coding sequences with altered expression in the absence of Vru. These consisted of known and putative virulence determinants, including Lbp (Sub0145), SclB (Sub1095), PauA (Sub1785) and hasA (Sub1696).
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Affiliation(s)
- Sharon A Egan
- The School of Veterinary Medicine and Science, The University of Nottingham, Sutton Bonington Campus, Sutton Bonington, Leicestershire LE12 5RD, UK
| | - Philip N Ward
- Nuffield Department of Clinical Laboratory Sciences, Oxford University, John Radcliffe Hospital, Headington, Oxfordshire OX3 9DU, UK
| | - Michael Watson
- Institute for Animal Health, Compton, Berkshire RG20 7NN, UK.,ARK-Genomics, The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK
| | - Terence R Field
- Institute for Animal Health, Compton, Berkshire RG20 7NN, UK
| | - James A Leigh
- The School of Veterinary Medicine and Science, The University of Nottingham, Sutton Bonington Campus, Sutton Bonington, Leicestershire LE12 5RD, UK
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Xue X, Li J, Wang W, Sztajer H, Wagner-Döbler I. The global impact of the delta subunit RpoE of the RNA polymerase on the proteome of Streptococcus mutans. Microbiology (Reading) 2012; 158:191-206. [DOI: 10.1099/mic.0.047936-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Affiliation(s)
- Xiaoli Xue
- Research Group Microbial Communication, Division of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstr. 7, D-38124 Braunschweig, Germany
| | - Jinshan Li
- Institute of Microbiology, Chinese Academy of Sciences, No. 1 West Beichen Road, Chaoyang District, 100101 Beijing, PR China
- Institute of Bioprocess and Biosystems Engineering, Technical University Hamburg-Harburg, Denickestr. 15, D-21071 Hamburg, Germany
| | - Wei Wang
- Institute of Bioprocess and Biosystems Engineering, Technical University Hamburg-Harburg, Denickestr. 15, D-21071 Hamburg, Germany
| | - Helena Sztajer
- Research Group Microbial Communication, Division of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstr. 7, D-38124 Braunschweig, Germany
| | - Irene Wagner-Döbler
- Research Group Microbial Communication, Division of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstr. 7, D-38124 Braunschweig, Germany
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16
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Martinez MA, Zaballa ME, Schaeffer F, Bellinzoni M, Albanesi D, Schujman GE, Vila AJ, Alzari PM, de Mendoza D. A novel role of malonyl-ACP in lipid homeostasis. Biochemistry 2010; 49:3161-7. [PMID: 20201588 DOI: 10.1021/bi100136n] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The FapR protein of Bacillus subtilis has been shown to play an important role in membrane lipid homeostasis. FapR acts as a repressor of many genes involved in fatty acid and phospholipid metabolism (the fap regulon). FapR binding to DNA is antagonized by malonyl-CoA, and thus FapR acts as a sensor of the status of fatty acid biosynthesis. However, malonyl-CoA is utilized for fatty acid synthesis only following its conversion to malonyl-ACP, which plays a central role in the initiation and elongation cycles carried out by the type II fatty acid synthase. Using in vitro transcription studies and isothermal titration calorimetry, we show here that malonyl-ACP binds FapR, disrupting the repressor-operator complex with an affinity similar to that of its precursor malonyl-CoA. NMR experiments reveal that there is no protein-protein recognition between ACP and FapR. These findings are consistent with the crystal structure of malonyl-ACP, which shows that the malonyl-phosphopantetheine moiety protrudes away from the protein core and thus can act as an effector ligand. Therefore, FapR regulates the expression of the fap regulon in response to the composition of the malonyl-phosphopantetheine pool. This mechanism ensures that fatty acid biosynthesis in B. subtilis is finely regulated at the transcriptional level by sensing the concentrations of the two first intermediates (malonyl-CoA and malonyl-ACP) in order to balance the production of membrane phospholipids.
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Affiliation(s)
- Mariano A Martinez
- Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina
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17
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Martinez MA, de Mendoza D, Schujman GE. Transcriptional and functional characterization of the gene encoding acyl carrier protein in Bacillus subtilis. MICROBIOLOGY-SGM 2009; 156:484-495. [PMID: 19850612 DOI: 10.1099/mic.0.033316-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Acyl carrier protein (ACP) is a universal and highly conserved carrier of acyl intermediates during fatty acid biosynthesis. The molecular mechanisms of regulation of the acpP structural gene, as well as the function of its gene product, are poorly characterized in Bacillus subtilis and other Gram-positive organisms. Here, we report that transcription of acpP takes place from two different promoters: PfapR and PacpP. Expression of acpP from PfapR is coordinated with a cluster of genes involved in lipid synthesis (the fapR operon); the operon consists of fapR-plsX-fabD-fabG-acpP. PacpP is located immediately upstream of the acpP coding sequence, and is necessary and sufficient for normal fatty acid synthesis. We also report that acpP is essential for growth and differentiation, and that ACP localizes in the mother-cell compartment of the sporangium during spore formation. These results provide the first detailed characterization of the expression of the ACP-encoding gene in a Gram-positive bacterium, and highlight the importance of this protein in B. subtilis physiology.
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Affiliation(s)
- Mariano A Martinez
- Instituto de Biología Molecular y Celular de Rosario, and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Diego de Mendoza
- Instituto de Biología Molecular y Celular de Rosario, and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Gustavo E Schujman
- Instituto de Biología Molecular y Celular de Rosario, and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
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18
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CcpA and LacD.1 affect temporal regulation of Streptococcus pyogenes virulence genes. Infect Immun 2009; 78:241-52. [PMID: 19841076 DOI: 10.1128/iai.00746-09] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Production of H(2)O(2) follows a growth phase-dependent pattern that mimics that of many virulence factors of Streptococcus pyogenes. To gain greater insight into mechanisms coupling virulence factor expression to growth phase, we investigated the molecular basis for H(2)O(2) generation and its regulation. Deletion of the gene encoding lactate oxidase (lctO) or culture in the presence of glucose eliminated H(2)O(2) production, implicating carbohydrate regulation of lctO as a key element of growth phase control. In examining known carbohydrate-responsive regulators, deletion of the gene encoding CcpA but not that encoding LacD.1 resulted in both derepression and an uncoupling of lctO transcription from its growth phase pattern. Expanding this analysis to additional virulence factors demonstrated both negative (cfa, encoding CAMP factor) and positive (speB, encoding a cysteine protease) regulation by CcpA and that CcpA mutants were highly cytotoxic for cultured macrophages. This latter property resulted from enhanced transcription of the streptolysin S biogenesis operon. Examination of CcpA-promoter interactions using a DNA pull-down assay mimicking physiological conditions showed direct binding to the promoters of lctO and speB but not those of sagA. CcpA but not LacD.1 mutants were attenuated in a murine model of soft-tissue infection, and analysis of gene expression in infected tissue indicated that CcpA mutants had altered expression of lctO, cfa, and speB but not the indirectly regulated sagA gene. Taken together, these data show that CcpA regulates virulence genes via at least three distinct mechanisms and that disruption of growth phase regulation alters transcriptional patterns in infected tissues.
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19
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emm1/sequence type 28 strains of group A streptococci that express covR at early stationary phase are associated with increased growth and earlier SpeB secretion. J Clin Microbiol 2009; 47:3161-9. [PMID: 19710271 DOI: 10.1128/jcm.00202-09] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Streptococcus pyogenes (group A streptococcus [GAS]) is a versatile human pathogen, and emm1/sequence type 28 (ST28) is the most frequently isolated type from GAS infections. The emm1/ST28 strain is associated with necrotizing fasciitis and streptococcal toxic shock syndrome. Growth-phase regulation is one of the important regulatory mechanisms in GAS, which controls gene expression at restricted phases of growth. CovRS, a two-component regulatory system, is considered the regulator of streptococcal pyrogenic exotoxin B (SpeB) and is thought to be activated in the exponential phase of growth. In the present study, Northern hybridization analysis showed that 52% of the analyzed GAS strains expressed covR at the exponential phase, but 48% of the strains expressed covR at the early stationary phase of growth. Strains transcribing covR at the early stationary phase showed better growth and earlier SpeB expression than the other group of strains. Multilocus sequence typing and pulsed-field gel electrophoresis analysis showed only emm1/ST28 strains (which comprise a clonal cluster) were expressing covR at the early stationary phase of growth, indicating that emm1/ST28 strains have special characteristics which may be related to their worldwide distribution.
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20
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Generation of metabolically diverse strains of Streptococcus pyogenes during survival in stationary phase. J Bacteriol 2009; 191:6242-52. [PMID: 19666718 DOI: 10.1128/jb.00440-09] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Streptococcus pyogenes, in addition to causing fulminant disease, can be carried asymptomatically and may survive in the host without causing disease. Long-term stationary-phase cultures were used to characterize the metabolism of cultures surviving after glucose depletion. Survival of stationary-phase cultures in glucose-depleted rich medium was truncated by switching the cells to phosphate-buffered saline or by the addition of antibiotics, suggesting that survival depended on the presence of nutrients and metabolic activity. The metabolites of the pyruvate-to-acetate (PA) pathway (acetate and formate) and amino acid catabolic pathways (ammonia) accumulated throughout long-term stationary phase (12 weeks). Acid and ammonia production was balanced so that the culture pH was maintained above pH 5.6. Strains isolated from long-term stationary-phase cultures accumulated mutations that resulted in unique exponential-phase metabolisms, with some strains expressing the PA pathway, some strains producing ammonia, and some strains expressing both in the presence of glucose. Strains expressing high levels of PA pathway activity during exponential growth were unable to survive when regrown in pure culture due to the production of excess acid. These data suggest that S. pyogenes diversifies during survival in stationary phase into distinct strains with different metabolisms and that complementary metabolism is required to control the pH in stationary-phase cultures. One of three survivor strains isolated from tonsillar discard material from patients expressed high levels of the PA pathway during exponential growth. Sequencing of multiple group A streptococcus regulators revealed two different mutations in two different strains, suggesting that random mutation occurs during survival.
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21
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Churchward G, Bates C, Gusa AA, Stringer V, Scott JR. Regulation of streptokinase expression by CovR/S in Streptococcus pyogenes: CovR acts through a single high-affinity binding site. MICROBIOLOGY-SGM 2009; 155:566-575. [PMID: 19202105 DOI: 10.1099/mic.0.024620-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The important human pathogen Streptococcus pyogenes (the group A streptococcus or GAS) produces many virulence factors that are regulated by the two-component signal transduction system CovRS (CsrRS). Dissemination of GAS infection originating at the skin has been shown to require production of streptokinase, whose transcription is repressed by CovR. In this work we have studied the interaction of CovR and phosphorylated CovR (CovR-P) with the promoter for streptokinase, Pska. We found that, in contrast to the other CovR-repressed promoters, Pska regulation by CovR occurs through binding at a single ATTARA consensus binding sequence (CB) that overlaps the -10 region of the promoter. Binding of CovR to other nearby consensus sequences occurs upon phosphorylation of the protein, but these other CBs do not contribute to the regulation of Pska by CovR. Thus, binding at a specific site does not necessarily indicate that the site is involved in regulation by CovR. In addition, at Pska, CovR binding to the different sites does not appear to involve cooperative interactions, which simplifies the analysis of CovR binding and gives us insight into the modes of interaction that occur between CovR and its specific DNA-binding sites. Finally, the observation that regulation of transcription from Pska occurs at a very low concentration of phosphorylated CovR may have important implications for the regulation of virulence gene expression during GAS infection.
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Affiliation(s)
- Gordon Churchward
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Christopher Bates
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Asiya A Gusa
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Virginia Stringer
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - June R Scott
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA
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22
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Sitkiewicz I, Musser JM. Analysis of growth-phase regulated genes in Streptococcus agalactiae by global transcript profiling. BMC Microbiol 2009; 9:32. [PMID: 19208240 PMCID: PMC2660347 DOI: 10.1186/1471-2180-9-32] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Accepted: 02/10/2009] [Indexed: 01/04/2023] Open
Abstract
Background Bacteria employ multiple mechanisms to control gene expression and react to their constantly changing environment. Bacterial growth in rich laboratory medium is a dynamic process in which bacteria utilize nutrients from simple to complex and change physical properties of the medium, as pH, during the process. To determine which genes are differentially expressed throughout growth from mid log to stationary phase, we performed global transcript analysis. Results The S. agalactiae transcriptome is dynamic in response to growth conditions. Several genes and regulons involved in virulence factor production and utilization of alternate carbon sources were differentially expressed throughout growth. Conclusion These data provide new information about the magnitude of plasticity of the S. agalactiae transcriptome and its adaptive response to changing environmental conditions. The resulting information will greatly assist investigators studying S. agalactiae physiology and pathogenesis.
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Affiliation(s)
- Izabela Sitkiewicz
- Center for Molecular and Translational Human Infectious Diseases Research, The Methodist Hospital Research Institute, Houston, Texas 77030, USA.
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23
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TrxR, a new CovR-repressed response regulator that activates the Mga virulence regulon in group A Streptococcus. Infect Immun 2008; 76:4659-68. [PMID: 18678666 DOI: 10.1128/iai.00597-08] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Coordinate regulation of virulence factors by the group A streptococcus (GAS) Streptococcus pyogenes is important in this pathogen's ability to cause disease. To further elucidate the regulatory network in this human pathogen, the CovR-repressed two-component system (TCS) trxSR was chosen for further analysis based on its homology to a virulence-related TCS in Streptococcus pneumoniae. In a murine skin infection model, an insertion mutation in the response regulator gene, trxR, led to a significant reduction in lesion size, lesion severity, and lethality. Curing the trxR mutation restored virulence comparable to the wild-type strain. The trxSR operon was defined in vivo, and CovR was found to directly repress its promoter in vitro. DNA microarray analysis established that TrxR activates transcription of Mga-regulated virulence genes, which may explain the virulence attenuation of the trxR mutant. This regulation appears to occur by activation of the mga promoter, Pmga, as demonstrated by analysis of a luciferase reporter fusion. Complementation of the trxR mutant with trxR on a plasmid restored expression of Mga regulon genes and restored virulence in the mouse model to wild-type levels. TrxR is the first TCS shown to regulate Mga expression. Because it is CovR repressed, TrxR defines a new pathway by which CovR can influence Mga to affect pathogenesis in the GAS.
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24
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Abstract
Spo0A, a classical two-component-type response regulator in Bacillus subtilis, binds to a specific DNA sequence found in many promoters to repress or activate the transcription of over 100 genes. On the spoIIG promoter, one of the Spo0A binding sites, centered at position -40, overlaps a consensus -35 element that may also interact with region 4 of the sigma A (sigma(A)) subunit of RNA polymerase. Molecular modeling corroborated by genetic evidence led us to propose that the binding of Spo0A to this site repositions sigma(A) region 4 on the promoter. Therefore, we used a chemical nuclease, p-bromoacetamidobenzyl-EDTA-Fe, that was covalently tethered to a single cysteine in region 4 of sigma(A) to map the position of sigma(A) on the promoter. The results indicated that in the absence of Spo0A, sigma(A) region 4 of the RNA polymerase was located near the -35 element sequence centered at position -40. However, in the presence of Spo0A, sigma(A) region 4 was displaced downstream from the -35 element by 4 bp. These and other results support the model in which the binding of Spo0A to the spoIIG promoter stimulates promoter utilization by repositioning prebound RNA polymerase and stabilizing the repositioned RNA polymerase-promoter complex at a new position that aligns sigma(A) region 2 with the -10 region sequences of the promoter, thus facilitating open complex formation.
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25
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26
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Roberts SA, Scott JR. RivR and the small RNA RivX: the missing links between the CovR regulatory cascade and the Mga regulon. Mol Microbiol 2007; 66:1506-22. [PMID: 18005100 DOI: 10.1111/j.1365-2958.2007.06015.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The CovR/S two-component system regulates the transcription of many genes that are crucial for the virulence of Streptococcus pyogenes (group A Streptococcus, GAS). Previously, we demonstrated that one gene repressed directly by CovR is rivR, which encodes a member of the RofA-like family of transcriptional regulators. In this study, we deleted rivR and its downstream gene rivX in a DeltacovR background. Microarray analysis revealed that the products of the rivRX locus exert positive control over the transcription of members of the Mga regulon. Using mutational analysis, we established that rivX encodes a small regulatory RNA. We found that RivR enhances transcriptional activation by Mga in vivo and in vitro. An M1 DeltacovRDeltarivRX strain is attenuated for virulence in a murine model of invasive soft tissue infection and this attenuation is complemented by rivRX expressed from a plasmid, demonstrating the importance of the rivRX locus in pathogenesis. This study provides the first link between the CovR and Mga regulatory networks. By integrating the signals received through these two global regulators, GAS is able to select from its repertoire different combinations of specific virulence factors to express in response to a broad spectrum of environmental conditions.
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Affiliation(s)
- Samantha A Roberts
- Department of Microbiology and Immunology, School of Medicine, Emory University, Atlanta, GA 30322, USA
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27
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Abstract
The group A streptococcus (GAS) causes a variety of human diseases, including toxic shock syndrome and necrotizing fasciitis, which are both associated with significant mortality. Even the superficial self-limiting diseases caused by GAS, such as pharyngitis, impose a significant economic burden on society. GAS can cause a wide spectrum of diseases because it elaborates virulence factors that enable it to spread and survive in different environmental niches within the human host. The production of many of these virulence factors is directly controlled by the activity of the CovR/S two-component regulatory system. CovS acts in one direction as a kinase primarily to activate the response regulator CovR and repress the expression of major virulence factors and in the other direction as a phosphatase to permit gene expression in response to environmental changes that mimic conditions found during human infection. This Janus-like behaviour of the CovR/S system is recapitulated in the binding of CovR to the promoters that it directly regulates. Interactions between different faces of the CovR DNA binding domain appear to depend upon DNA sequence, leading to the potential for differential regulation of virulence gene expression.
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Affiliation(s)
- Gordon Churchward
- Department of Microbiology and Immunology, Emory University, Atlanta, GA 30322, USA.
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28
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Dmitriev AV, McDowell EJ, Kappeler KV, Chaussee MA, Rieck LD, Chaussee MS. The Rgg regulator of Streptococcus pyogenes influences utilization of nonglucose carbohydrates, prophage induction, and expression of the NAD-glycohydrolase virulence operon. J Bacteriol 2006; 188:7230-41. [PMID: 17015662 PMCID: PMC1636216 DOI: 10.1128/jb.00877-06] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The expression of many virulence-associated genes in Streptococcus pyogenes is controlled in a growth phase-dependent manner. Unlike the model organisms Escherichia coli and Bacillus subtilis, such regulation is apparently not dependent upon alternative sigma factors but appears to rely on complex interactions among several transcriptional regulators, including Rgg. The purpose of this study was to identify changes in gene expression associated with inactivation of the rgg gene in S. pyogenes strain NZ131 (serotype M49). To this end, the transcriptomes of wild-type and rgg mutant strains were analyzed during both the exponential and postexponential phases of growth using Affymetrix NimbleExpress gene chips. Genomewide differences in transcript levels were identified in both phases of growth. Inactivation of rgg disrupted coordinate expression of genes associated with the metabolism of nonglucose carbon sources, such as fructose, mannose, and sucrose. The changes were associated with an inability of the mutant strain to grow using these compounds as the primary carbon source. Bacteriophage transcript levels were also altered in the mutant strain and were associated with decreased induction of at least one prophage. Finally, transcripts encoding virulence factors involved in cytolysin-mediated translocation of NAD-glycohydrolase, including the immunity factor IFS and the cytolysin (streptolysin O [SLO]), were more abundant in the mutant strain, which correlated with the amount of NADase and SLO activities in culture supernatant fluids. The results provide further evidence that Rgg contributes to growth phase-dependent gene regulation in strain NZ131.
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Affiliation(s)
- Alexander V Dmitriev
- Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Lee Medical Building, 414 East Clark Street, Vermillion, SD 57069-2390, USA
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29
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Gusa AA, Froehlich BJ, Desai D, Stringer V, Scott JR. CovR activation of the dipeptide permease promoter (PdppA) in Group A Streptococcus. J Bacteriol 2006; 189:1407-16. [PMID: 16997962 PMCID: PMC1797356 DOI: 10.1128/jb.01036-06] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
CovR, the two-component response regulator of Streptococcus pyogenes (group A streptococcus [GAS]) directly or indirectly represses about 15% of the genome, including genes encoding many virulence factors and itself. Transcriptome analyses also showed that some genes are activated by CovR. We asked whether the regulation by CovR of one of these genes, dppA, the first gene in an operon encoding a dipeptide permease, is direct or indirect. Direct regulation by CovR was suggested by the presence of five CovR consensus binding sequences (CBs) near the putative promoter. In this study, we identified the 5' end of the dppA transcript synthesized in vivo and showed that the start of dppA transcription in vitro is the same. We found that CovR binds specifically to the dppA promoter region (PdppA) in vitro with an affinity similar to that at which it binds to other CovR-regulated promoters. Disruption of any of the five CBs by a substitution of GG for TT inhibited CovR binding to that site in vitro, and binding at two of the CBs appeared cooperative. In vivo, CovR activation of transcription was not affected by individual mutations of any of the four CBs that we could study. This suggests that the binding sites are redundant in vivo. In vitro, CovR did not activate transcription from PdppA in experiments using purified GAS RNA polymerase and either linear or supercoiled DNA template. Therefore, we propose that in vivo, CovR may interfere with the binding of a repressor of PdppA.
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Affiliation(s)
- Asiya A Gusa
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA
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30
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Schujman GE, Guerin M, Buschiazzo A, Schaeffer F, Llarrull LI, Reh G, Vila AJ, Alzari PM, de Mendoza D. Structural basis of lipid biosynthesis regulation in Gram-positive bacteria. EMBO J 2006; 25:4074-83. [PMID: 16932747 PMCID: PMC1560364 DOI: 10.1038/sj.emboj.7601284] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2006] [Accepted: 07/25/2006] [Indexed: 11/08/2022] Open
Abstract
Malonyl-CoA is an essential intermediate in fatty acid synthesis in all living cells. Here we demonstrate a new role for this molecule as a global regulator of lipid homeostasis in Gram-positive bacteria. Using in vitro transcription and binding studies, we demonstrate that malonyl-CoA is a direct and specific inducer of Bacillus subtilis FapR, a conserved transcriptional repressor that regulates the expression of several genes involved in bacterial fatty acid and phospholipid synthesis. The crystal structure of the effector-binding domain of FapR reveals a homodimeric protein with a thioesterase-like 'hot-dog' fold. Binding of malonyl-CoA promotes a disorder-to-order transition, which transforms an open ligand-binding groove into a long tunnel occupied by the effector molecule in the complex. This ligand-induced modification propagates to the helix-turn-helix motifs, impairing their productive association for DNA binding. Structure-based mutations that disrupt the FapR-malonyl-CoA interaction prevent DNA-binding regulation and result in a lethal phenotype in B. subtilis, suggesting this homeostatic signaling pathway as a promising target for novel chemotherapeutic agents against Gram-positive pathogens.
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Affiliation(s)
- Gustavo E Schujman
- Instituto de Biología Molecular y Celular de Rosario (IBR), Universidad Nacional de Rosario, Rosario, Argentina
- Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Marcelo Guerin
- Unité de Biochimie Structurale & URA 2185 CNRS, Institut Pasteur, Paris, France
| | | | - Francis Schaeffer
- Unité de Biochimie Structurale & URA 2185 CNRS, Institut Pasteur, Paris, France
| | - Leticia I Llarrull
- Instituto de Biología Molecular y Celular de Rosario (IBR), Universidad Nacional de Rosario, Rosario, Argentina
- Departamento de Química Biológica, Área Biofísica, Universidad Nacional de Rosario, Rosario, Argentina
| | - Georgina Reh
- Instituto de Biología Molecular y Celular de Rosario (IBR), Universidad Nacional de Rosario, Rosario, Argentina
- Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Alejandro J Vila
- Instituto de Biología Molecular y Celular de Rosario (IBR), Universidad Nacional de Rosario, Rosario, Argentina
- Departamento de Química Biológica, Área Biofísica, Universidad Nacional de Rosario, Rosario, Argentina
| | - Pedro M Alzari
- Unité de Biochimie Structurale & URA 2185 CNRS, Institut Pasteur, Paris, France
- Unité de Biochimie Structurale, Institut Pasteur, URA 2185 CNRS, 25 rue du Docteur Roux, Paris 75724, France. Tel.: +33 1 4568 8607; Fax: +33 1 4568 8604; E-mail:
| | - Diego de Mendoza
- Instituto de Biología Molecular y Celular de Rosario (IBR), Universidad Nacional de Rosario, Rosario, Argentina
- Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
- IBR-CONICET, Suipacha 531, Rosario 2000, Argentina. Tel.: +54 341 435 1235 ext 111; Fax: +54 341 439-0465; E-mail:
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31
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Woodbury RL, Wang X, Moran CP. Sigma X induces competence gene expression in Streptococcus pyogenes. Res Microbiol 2006; 157:851-6. [PMID: 16963231 DOI: 10.1016/j.resmic.2006.07.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Revised: 06/29/2006] [Accepted: 07/11/2006] [Indexed: 01/31/2023]
Abstract
Although not thought to become competent for DNA uptake, the bacterium Streptococcus pyogenes appears to encode within its genome the DNA uptake and recombination machinery required for competence. The promoters of these genes contain a conserved sequence, CIN-box, which is recognized by the S. pyogenes alternative RNA polymerase sigma factor X. Using microarray technology, we found that sigma X induced the expression of competence genes in S. pyogenes. Real-time RT-PCR was performed to confirm that the expression of these transcripts was induced 2-265-fold by sigma X. Of the eight CIN-box loci induced, femB, the ortholog a virulence factor in Staphylococcus aureus, was shown to be transcribed in vitro by RNA polymerase containing sigma X, indicating that sigma X directly activates expression of this CIN-box gene. Sigma X-dependent induction of genes encoding competence machinery in S. pyogenes raises the possibility that some strains of this human pathogen can develop competence for genetic transformation.
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Affiliation(s)
- Robyn L Woodbury
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA
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Heng NCK, Tagg JR, Tompkins GR. Identification and characterization of the loci encoding the competence-associated alternative sigma factor of Streptococcus gordonii. FEMS Microbiol Lett 2006; 259:27-34. [PMID: 16684098 DOI: 10.1111/j.1574-6968.2006.00238.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
In naturally-competent streptococci such as Streptococcus pneumoniae, expression of the late competence operons is regulated by ComX (sigma(X)), the competence-specific alternative sigma factor. In this study, duplicate genes (comR1 and comR2) encoding the putative ComX homologue of the oral bacterium Streptococcus gordonii were identified. Like the identical twin comX loci of S. pneumoniae, both comR determinants are independently functional as well as responsive to the ComDE signal transduction system activated by competence-stimulating peptide. However, in contrast to the comX system, nucleotide sequence analyses in combination with in trans complementation studies with a comR null mutant demonstrate that the identical 83 bp tracts (Region I) located immediately upstream of the comR structural genes are insufficient to confer wild-type competence levels. Wild-type transformation levels required additional distal nonhomologous DNA segments (Region II). Our findings suggest that alternative regulatory elements, under overall control of the ComDE pathway, may influence expression of the comR loci.
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Affiliation(s)
- Nicholas C K Heng
- Department of Oral Sciences, University of Otago School of Dentistry, Dunedin, New Zealand.
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Martin B, Quentin Y, Fichant G, Claverys JP. Independent evolution of competence regulatory cascades in streptococci? Trends Microbiol 2006; 14:339-45. [PMID: 16820295 DOI: 10.1016/j.tim.2006.06.007] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Revised: 05/11/2006] [Accepted: 06/15/2006] [Indexed: 02/02/2023]
Abstract
Natural genetic transformation is a mechanism of horizontal gene transfer that is widely distributed in bacteria and requires assembly of a DNA uptake machinery. Transformable bacteria use fundamentally the same machine, which in most species is assembled only in cells that are developing competence. Competence regulation usually differs between unrelated species. Here, we examine whether related streptococci use the same competence regulatory cascade. Phylogenetic analyses of streptococcal genome sequences reveal the existence of two paralogous two-component regulatory systems, either of which might control competence. This suggests the distribution of streptococci into two groups that use competence regulatory cascades that have at least partly evolved independently. Comparison of data obtained with two transformable streptococci, Streptococcus pneumoniae and Streptococcus mutans, provides support to this suggestion.
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Affiliation(s)
- Bernard Martin
- Laboratoire de Microbiologie et Génétique Moléculaires, UMR 5100 CNRS-Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex 9, France
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Almengor AC, Walters MS, McIver KS. Mga is sufficient to activate transcription in vitro of sof-sfbX and other Mga-regulated virulence genes in the group A Streptococcus. J Bacteriol 2006; 188:2038-47. [PMID: 16513733 PMCID: PMC1428152 DOI: 10.1128/jb.188.6.2038-2047.2006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The group A streptococcus (GAS), or Streptococcus pyogenes, is a strict human pathogen of medical significance, causing infections ranging from pharyngitis (strep throat) to necrotizing fasciitis (flesh-eating disease). Several virulence genes that encode factors important for colonization, internalization, and immune evasion are under the control of the multiple gene regulator of the GAS, or Mga. Mga functions as a DNA-binding protein that interacts with sites both proximal (Pemm and PscpA) and distal (PsclA) to the start of transcription for the genes that it regulates. The genes encoding serum opacity factor, sof, and a novel fibronectin-binding protein, sfbX, are cotranscribed and represent two uncharacterized Mga-regulated virulence genes in the GAS. Analysis of the promoter region of sof-sfbX identified a putative Mga-binding site 278 bp upstream of the regulated start of transcription as determined by primer extension. Electrophoretic mobility shift assays demonstrated that Mga is able to bind specifically to the single distal site in a fashion similar to the previously characterized PsclA. In order to better understand the events that take place at this and other Mga-regulated promoters, an in vitro transcription assay was established. Using this assay, we showed that Mga is sufficient to activate transcription in vitro for Mga-regulated promoters containing both proximal (Pemm) and distal (PsclA and Psof-sfbX) binding sites. These results indicate that additional factors are not required for Mga-specific activation at diverse promoters in vitro, although they do not rule out the potential influence of other components on the Mga virulence regulon in vivo.
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Affiliation(s)
- Audry C Almengor
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9048, USA
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35
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Gusa AA, Scott JR. The CovR response regulator of group A streptococcus (GAS) acts directly to repress its own promoter. Mol Microbiol 2005; 56:1195-207. [PMID: 15882414 DOI: 10.1111/j.1365-2958.2005.04623.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The CovR/S (CsrR/S) two component system is a global regulator of virulence gene expression in the group A streptococcus (GAS, Streptococcus pyogenes). The response regulator, CovR, regulates about 15% of the genes of GAS, including its own operon. Using in vitro DNA binding assays with purified CovR protein, we found that CovR binds a DNA fragment including the covR promoter (Pcov). DNaseI footprint analyses showed that phosphorylation of CovR enhanced and extended the protected regions. The proposed CovR consensus binding sequence (ATTARA) was present at most, but not all protected regions. The effect of replacing the two thymine residues in the consensus binding sequence (CB) with guanine residues was evaluated both in vitro and in vivo. Most, but not all, CB mutations reduced binding of CovR in vitro. Using a transcriptional reporter introduced in single copy into the GAS chromosome, we found that mutations at each CB completely or partially relieved CovR-mediated repression in vivo. This suggests that CovR regulation of Pcov is direct. Further support for this conclusion comes from use of an in vitro GAS transcription system in which CovR was sufficient to mediate repression of Pcov. This repression was enhanced by phosphorylation of the protein. In addition, we found that the CovR binding region overlapping the promoter was essential for wild type repression of Pcov both in vitro and in vivo, suggesting that promoter occlusion is a primary mechanism of Pcov repression by CovR.
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Affiliation(s)
- Asiya A Gusa
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA
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Chaussee MA, Callegari EA, Chaussee MS. Rgg regulates growth phase-dependent expression of proteins associated with secondary metabolism and stress in Streptococcus pyogenes. J Bacteriol 2004; 186:7091-9. [PMID: 15489420 PMCID: PMC523193 DOI: 10.1128/jb.186.21.7091-7099.2004] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The transcriptional regulatory protein Rgg coordinates amino acid catabolism and virulence factor expression in Streptococcus pyogenes. We used a proteomic approach to compare cytoplasmic proteins isolated from S. pyogenes wild-type strain NZ131 (serotype M49) to proteins isolated from an rgg mutant strain during the exponential and stationary phases of growth. Proteins were separated by two-dimensional gel electrophoresis, and 125 protein spots of interest were identified by tandem mass spectrometry. Comparative analysis of proteins isolated from the isogenic strains revealed that growth phase-associated regulation of enzymes involved in the metabolism of arginine (ArcABC), histidine (HutI), and serine (SdhA) was abrogated in the rgg mutant strain, which synthesized the proteins in the exponential phase of growth. In contrast, the enzymes were detected only among wild-type proteins isolated from organisms in the stationary phase of growth. The differences in protein composition were correlated with previously described metabolic changes. In addition, proteins associated with thermal and oxidative stress responses, including ClpE and ClpL, were present in samples isolated from the rgg mutant strain but not in samples isolated from the wild-type strain. The rgg mutant strain was more tolerant to elevated temperature and puromycin than the wild-type strain; however, the mutant was less tolerant to paraquat. We concluded that Rgg is a global regulatory factor that contributes to growth phase-dependent synthesis of proteins associated with secondary metabolism and oxidative and thermal stress responses.
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Affiliation(s)
- Michelle A Chaussee
- Division of Basic Biomedical Sciences, University of South Dakota College of Medicine, Lee Medical Building, 414 East Clark Street, Vermillion, SD 57069-2390, USA.
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Luo P, Li H, Morrison DA. ComX is a unique link between multiple quorum sensing outputs and competence in Streptococcus pneumoniae. Mol Microbiol 2004; 50:623-33. [PMID: 14617184 DOI: 10.1046/j.1365-2958.2003.03714.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Natural competence for genetic transformation in Streptococcus pneumoniae is achieved directly by specific proteins that are involved in DNA uptake and chromosomal recombination, and is regulated indirectly by a quorum-sensing system encoded by two loci, comAB and comCDE. The alternative sigma factor, ComX, is thought to be the unique link between quorum sensing and competence-specific genes. To test this hypothesis, we replaced the quorum-sensing inducible promoter (PQ) of the comX gene with either a constitutive promoter (PC) or a raffinose-inducible promoter (PR), so that comX transcription would be independent of quorum sensing. Surprisingly, both competence and expression of late genes, such as ssbB, cglA or celB, were found to depend on CSP in these mutants. An unknown, CSP-dependent regulator was needed when comX was expressed from these ectopic promoters, and it appears to act post-transcriptionally. However, when a multicopy nisin-inducible ComX-overexpressing plasmid was introduced, pneumococcal cells developed competence in the presence of nisin even despite deletion of comE. At 1% of the normal protein peak level, ComX protein stimulated competence without the participation of the pheromone response circuit. Thus, ComX is a unique link to competence-specific genes, but depends on multiple outputs of quorum sensing for maximal expression.
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Affiliation(s)
- Ping Luo
- Laboratory for Molecular Biology, Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
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Peterson SN, Sung CK, Cline R, Desai BV, Snesrud EC, Luo P, Walling J, Li H, Mintz M, Tsegaye G, Burr PC, Do Y, Ahn S, Gilbert J, Fleischmann RD, Morrison DA. Identification of competence pheromone responsive genes in Streptococcus pneumoniae by use of DNA microarrays. Mol Microbiol 2003; 51:1051-70. [PMID: 14763980 DOI: 10.1046/j.1365-2958.2003.03907.x] [Citation(s) in RCA: 282] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Natural genetic transformation in Streptococcus pneumoniae is controlled in part by a quorum-sensing system mediated by a peptide pheromone called competence-stimulating peptide (CSP), which acts to coordinate transient activation of genes required for competence. To characterize the transcriptional response and regulatory events occurring when cells are exposed to competence pheromone, we constructed DNA microarrays and analysed the temporal expression profiles of 1817 among the 2129 unique predicted open reading frames present in the S. pneumoniae TIGR4 genome (84%). After CSP stimulation, responsive genes exhibited four temporally distinct expression profiles: early, late and delayed gene induction, and gene repression. At least eight early genes participate in competence regulation including comX, which encodes an alternative sigma factor. Late genes were dependent on ComX for CSP-induced expression, many playing important roles in transformation. Genes in the delayed class (third temporal wave) appear to be stress related. Genes repressed during the CSP response include ribosomal protein loci and other genes involved in protein synthesis. This study increased the number of identified CSP-responsive genes from approximately 40 to 188. Given the relatively large number of induced genes (6% of the genome), it was of interest to determine which genes provide functions essential to transformation. Many of the induced loci were subjected to gene disruption mutagenesis, allowing us to establish that among 124 CSP-inducible genes, 67 were individually dispensable for transformation, whereas 23 were required for transformation.
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Affiliation(s)
- Scott N Peterson
- The Pathogen Functional Genomics Resource Center, The Institute for Genomic Research, Rockville, MD 20850, USA
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Opdyke JA, Scott JR, Moran CP. Expression of the secondary sigma factor sigmaX in Streptococcus pyogenes is restricted at two levels. J Bacteriol 2003; 185:4291-7. [PMID: 12867436 PMCID: PMC165779 DOI: 10.1128/jb.185.15.4291-4297.2003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Secondary RNA polymerase sigma factors in many bacteria are responsible for regulating a vast range of processes including virulence. A protein (sigma(X)) in the gram-positive human pathogen Streptococcus pyogenes (the group A Streptococcus or GAS) was recently shown to function in vitro as a secondary sigma factor. We report here the isolation of a mutant in which both sigX genes are inactivated, show that sigma(X) functions in GAS cells, and show that the amount of sigma(X) is controlled at two levels. Primer extension analysis indicates that sigX transcription is low in GAS cells grown in Todd-Hewitt yeast broth, and immunoblot assays with a sigma(X)-specific polyclonal antibody demonstrate that the protein does not accumulate in these cells. To increase the level of sigX transcription in GAS, we constructed a strain that constitutively expresses the sigX gene from a heterologous promoter. Expression of sigX from this promoter led to transcription of the sigma(X)-dependent cinA promoter in GAS cells. We found that expression of the sigX gene in a clpP mutant strain resulted in greater accumulation of sigma(X) protein, which resulted in higher levels of transcription from the sigma(X)-dependent promoters cinA, smf, and cglA. In addition, a clpP mutant containing sigX only at its wild-type loci on the chromosome generated more transcription from the sigma(X)-dependent cinA promoter than did the wild-type parental strain. Therefore, sigma(X) activity in GAS is limited by low-level transcription of the sigX structural genes and by clpP, which appears to negatively regulate sigma(X) accumulation.
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Affiliation(s)
- Jason A Opdyke
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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Morikawa K, Inose Y, Okamura H, Maruyama A, Hayashi H, Takeyasu K, Ohta T. A new staphylococcal sigma factor in the conserved gene cassette: functional significance and implication for the evolutionary processes. Genes Cells 2003; 8:699-712. [PMID: 12875655 DOI: 10.1046/j.1365-2443.2003.00668.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND Staphylococcus aureus is a major human pathogen and causes a serious hospital infection due to the acquired multidrug resistance. Unlike the well-studied bacteria such as Escherichia coli and Bacillus subtilis, which have seven and 18 sigma factors, respectively, only two sigma factors have been known for S. aureus. We searched for possible sigma factor genes by examining the S. aureus genome with a special attention to the gene arrangement around the sigma factor genes of a close relative, B. subtilis. RESULTS A new sigma factor gene was identified in Staphylococcus. The gene constituted a conserved gene cluster with other genes including translation- and transcription-related genes. Phylogenetic analysis and comparison of the gene sequences among species indicated that the staphylococcal sigma factor originated from a common ancestor of B. subtilis SigH. An over-expression of this sigma factor in S. aureus resulted in a drastic induction of the expression of the com operons that encode proteins required for the natural genetic competence. CONCLUSIONS We demonstrated that the newly identified staphylococcal sigma factor participated in a regulatory network of transcription that controlled the genetic competence genes. In our phylogenetic tree, the factor was classified as a single group with a common function.
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Affiliation(s)
- Kazuya Morikawa
- Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba, 305-8577 Japan
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Kreikemeyer B, McIver KS, Podbielski A. Virulence factor regulation and regulatory networks in Streptococcus pyogenes and their impact on pathogen-host interactions. Trends Microbiol 2003; 11:224-32. [PMID: 12781526 DOI: 10.1016/s0966-842x(03)00098-2] [Citation(s) in RCA: 228] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Streptococcus pyogenes (group A streptococcus, GAS) is a very important human pathogen with remarkable adaptation capabilities. Survival within the harsh host surroundings requires sensing potential on the bacterial side, which leads in particular to coordinately regulated virulence factor expression. GAS 'stand-alone' response regulators (RRs) and two-component signal transduction systems (TCSs) link the signals from the host environment with adaptive responses of the bacterial cell. Numerous putative regulatory systems emerged from GAS genome sequences. Only three RRs [Mga, RofA-like protein (RALP) and Rgg/RopB] and three TCSs (CsrRS/CovRS, FasBCAX and Ihk/Irr) have been studied in some detail with respect to their growth-phase-dependent activity and their influence on GAS-host cell interaction. In particular, the Mga-, RALP- and Rgg/RopB-regulated pathways display interconnected activities that appear to influence GAS colonization, persistence and spreading mechanisms, in a growth-phase-related fashion. Here, we have summarized our current knowledge about these RRs and TCSs to highlight the questions that should be addressed in future research on GAS pathogenicity.
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Affiliation(s)
- Bernd Kreikemeyer
- University Hospital Rostock, Department of Medical Microbiology and Hospital Hygiene, Schillingallee 70, 18055 Rostock, Germany.
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42
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Claverys JP, Martin B. Bacterial "competence" genes: signatures of active transformation, or only remnants? Trends Microbiol 2003; 11:161-5. [PMID: 12706993 DOI: 10.1016/s0966-842x(03)00064-7] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
An exhaustive review published ten years ago reported natural genetic transformation, a potential mechanism for intra- and interspecies gene transfer, in approximately 40 species belonging to different taxonomic and trophic groups. Since then, considerable progress has been made in characterizing DNA-uptake machineries and regulatory circuits controlling their expression in cells competent for genetic transformation. In this article, in light of the recent description of a Group A streptococcal isolate capable of DNA transfer in mixed cultures, we discuss whether the detection in completely sequenced microbial genomes of intact homologues of key competence-regulatory and/or DNA-uptake proteins enables the prediction of new transformable species.
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Affiliation(s)
- Jean-Pierre Claverys
- Laboratoire de Microbiologie et Génétique Moléculaires, UMR 5100 CNRS-Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex, France.
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43
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Luo P, Morrison DA. Transient association of an alternative sigma factor, ComX, with RNA polymerase during the period of competence for genetic transformation in Streptococcus pneumoniae. J Bacteriol 2003; 185:349-58. [PMID: 12486073 PMCID: PMC141820 DOI: 10.1128/jb.185.1.349-358.2003] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Natural transformation in Streptococcus pneumoniae is regulated by a quorum-sensing system that acts through accumulation and sensing of a peptide pheromone (competence-stimulating peptide [CSP]) to control many competence-specific genes acting in DNA uptake, processing, and integration. The period of competence induced by CSP lasts only 15 min (quarter-height peak width). The recently identified regulator ComX is required for the CSP-dependent expression of many competence-specific genes that share an unusual consensus sequence (TACGAATA) at their promoter regions. To test the hypothesis that this regulator acts as a transient alternative sigma factor, ComX was purified from an Escherichia coli overexpression strain and core RNA polymerase was purified from a comX-deficient S. pneumoniae strain. The reconstituted ComX-polymerase holoenzyme produced transcripts for the competence-specific genes ssbB, cinA, cglA, celA, and dalA and was inhibited by anti-ComX antibody, but not by anti-sigma(70) antibody. Western blotting using antibodies specific for ComX, sigma(70), and poly-His revealed a transient presence of ComX for a period of 15 to 20 min after CSP treatment, while RNA polymerase remained at a constant level and sigma(A) remained between 60 and 125% of its normal level. ComX reached a molar ratio to RNA polymerase of at least 1.5. We conclude that ComX is unstable and acts as a competence-specific sigma factor.
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Affiliation(s)
- Ping Luo
- Laboratory for Molecular Biology, Department of Biological Sciences, University of Illinois at Chicago, 900 S. Ashland Avenue, Chicago, IL 60607, USA
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Hidalgo-Grass C, Ravins M, Dan-Goor M, Jaffe J, Moses AE, Hanski E. A locus of group A Streptococcus involved in invasive disease and DNA transfer. Mol Microbiol 2002; 46:87-99. [PMID: 12366833 DOI: 10.1046/j.1365-2958.2002.03127.x] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Group A streptococcus (GAS) causes diseases ranging from benign to severe infections such as necrotizing fasciitis (NF). The reasons for the differences in severity of streptococcal infections are unexplained. We developed the polymorphic-tag-lengths-transposon-mutagenesis (PTTM) method to identify virulence genes in vivo. We applied PTTM on an emm14 strain isolated from a patient with NF and screened for mutants of decreased virulence, using a mouse model of human soft-tissue infection. A mutant that survived in the skin but was attenuated in its ability to reach the spleen and to cause a lethal infection was identified. The transposon was inserted into a small open reading frame (ORF) in a locus termed sil, streptococcal invasion locus. sil contains at least five genes (silA-E) and is highly homologous to the quorum-sensing competence regulons of Streptococcus pneumoniae. silA and silB encode a putative two-component system whereas silD and silE encode two putative ABC transporters. silC is a small ORF of unknown function preceded by a combox promoter. Insertion and deletion mutants of sil had a diminished lethality in the animal model. Virulence of a deletion mutant of silC was restored when injected together with the avirulent emm14-deletion mutant, but not when these mutants were injected into opposite flanks of a mouse. DNA transfer between these mutants occurred in vivo but could not account for the complementation of virulence. DNA exchange between the emm14-deletion mutant and mutants of sil occurred also in vitro, at a frequency of approximately 10-8 for a single antibiotic marker. Whereas silC and silD mutants exchanged markers with the emm14 mutant, silB mutant did not. Thus, we identified a novel locus, which controls GAS spreading into deeper tissues and could be involved in DNA transfer.
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Affiliation(s)
- Carlos Hidalgo-Grass
- Department of Clinical Microbiology, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
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