Variation in the Group B Streptococcus CsrRS Regulon and Effects on Pathogenicity

Division of Infectious Diseases, Children's Hospital Boston, 300 Longwood Ave., Boston, MA 02115, USA.
Journal of bacteriology (Impact Factor: 2.81). 04/2008; 190(6):1956-65. DOI: 10.1128/JB.01677-07
Source: PubMed


CsrRS (or CovRS) is a two-component regulatory system that controls expression of multiple virulence factors in the important
human pathogen group B Streptococcus (GBS). We now report global gene expression studies in GBS strains 2603V/R and 515 and their isogenic csrR and csrS mutants. Together with data reported previously for strain NEM316, the results reveal a conserved 39-gene CsrRS regulon.
In vitro phosphorylation-dependent binding of recombinant CsrR to promoter regions of both positively and negatively regulated
genes suggests that direct binding of CsrR can mediate activation as well as repression of target gene expression. Distinct
patterns of gene regulation in csrR versus csrS mutants in strain 2603V/R compared to 515 were associated with different hierarchies of relative virulence of wild-type,
csrR, and csrS mutants in murine models of systemic infection and septic arthritis. We conclude that CsrRS regulates a core group of genes
including important virulence factors in diverse strains of GBS but also displays marked variability in the repertoire of
regulated genes and in the relative effects of CsrS signaling on CsrR-mediated gene regulation. Such variation is likely to
play an important role in strain-specific adaptation of GBS to particular host environments and pathogenic potential in susceptible

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    • "The TCS CovRS (also known as CsrRS) is shared by several streptococcal species (including Group A Streptococcus or GAS) and is considered as the master regulator of virulence gene expression in GBS [8] [9]. Accordingly, the CovRS system regulates up to 7% of the GBS genes, most of which encode putative secreted or surface components, including several small molecule transport systems, cytolysins, and adhesins [7] [10]. "
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    ABSTRACT: Unlabelled: The two-component regulatory system CovRS is the main regulator of virulence gene expression in Group B Streptococcus (GBS), the leading cause of invasive infections in neonates. In this study we analyzed by mass spectrometry the GBS extracellular protein complex (i.e. the exoproteome) of NEM316 wild-type (WT) strain and its isogenic covRS deletion mutant (ΔcovRS). A total of 53 proteins, 49 of which had classical secretion signals, were identified: 12 were released by both strains while 21 and 20 were released exclusively by WT and ΔcovRS strains, respectively. In addition to known surface proteins, we detected here unstudied cell-wall associated proteins and/or orthologs of putative virulence factors present in other pathogenic streptococci. While the functional role of these proteins remains to be elucidated, our data suggest that the analysis of the exoproteome of bacterial pathogens under different gene expression conditions may be a powerful tool for the rapid identification of novel virulence factors and vaccine candidates. Biological significance: We believe that this manuscript will be of interest to Journal of Proteomics readers since the paper describes the identification of several putative virulence factors and vaccine candidates of the group B streptococcus, an important pathogen, using a simple proteomics strategy involving LC-MS analysis of culture supernatants obtained from two strains with divergent gene expression patterns. This technique provided the most comprehensive inventory of extracellular proteins obtained from a single streptococcal species thus far. The approach described has the added benefit of being easily applicable to a large number of different strains, making it ideal for the identification of conserved vaccine candidates.
    Journal of proteomics 06/2013; 89. DOI:10.1016/j.jprot.2013.06.003 · 3.89 Impact Factor
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    • "Probes were printed 5X on aminosilane-coated slides (SCHOTT Nexterion). The microarrays (version 6) were kindly provided by the Pathogen Functional Genomics Resource Center (PFGRC) at the J. Craig Venter Institute and experiments were performed as previously described [19]. Briefly, 2 μg of the total RNAs to be compared were reverse transcribed into single-stranded cDNA using 200 U Superscript II reverse transcriptase (Invitrogen), 6 μg random hexamers (Invitrogen), 1X first strand buffer (Invitrogen), 10 mM dithiothreitol (DTT), 0.5 mM dATP, 0.5 mM dCTP, 0.5 mM dGTP, 0.3 mM dTTP and 0.2 mM of aminoallyl-modified nucleotide (Invitrogen). "
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    ABSTRACT: Background Streptococcus pneumoniae is a leading cause of childhood morbidity and mortality worldwide, despite the availability of effective pneumococcal vaccines. Understanding the molecular interactions between the bacterium and the host will contribute to the control and prevention of pneumococcal disease. Results We used a combination of adherence assays, mutagenesis and functional genomics to identify novel factors involved in adherence. By contrasting these processes in two pneumococcal strains, TIGR4 and G54, we showed that adherence and invasion capacities vary markedly by strain. Electron microscopy showed more adherent bacteria in association with membranous pseudopodia in the TIGR4 strain. Operons for cell wall phosphorylcholine incorporation (lic), manganese transport (psa) and phosphate utilization (phn) were up-regulated in both strains on exposure to epithelial cells. Pneumolysin, pili, stress protection genes (adhC-czcD) and genes of the type II fatty acid synthesis pathway were highly expressed in the naturally more invasive strain, TIGR4. Deletion mutagenesis of five gene regions identified as regulated in this study revealed attenuation in adherence. Most strikingly, ∆SP_1922 which was predicted to contain a B-cell epitope and revealed significant attenuation in adherence, appeared to be expressed as a part of an operon that includes the gene encoding the cytoplasmic pore-forming toxin and vaccine candidate, pneumolysin. Conclusion This work identifies a list of novel potential pneumococcal adherence determinants.
    BMC Genomics 06/2013; 14(1):383. DOI:10.1186/1471-2164-14-383 · 3.99 Impact Factor
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    • "For analysis of the human host cell response, microarrays with PCR amplicons of 41,000 cDNA clones were used (kindly provided by Norman Lee at George Washington University, Washington, DC, USA). Preparation of labeled cDNA target and hybridization experiments were done as previously described [30] with the exception that for the human host cell response, the starting amount of RNA used to synthesize cDNA was 5 μg. Total RNA was isolated from 3 independent cultures (biological replicates) of TIGR4 strain and D562 cells. "
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    ABSTRACT: Background Viral upper respiratory tract infections are associated with increased colonization by Streptococcus pneumoniae but the mechanisms underlying this relationship are unclear. The objective of this study is to describe a comprehensive picture of the cellular interaction between the adhering bacteria and host cells in the presence or absence of a viral co-infection. Results Gene expression profiles of Detroit-562 pharyngeal cells, which were either mock-infected or infected with human respiratory syncytial virus (RSV) or human parainfluenza virus 3 (HPIV3), were analyzed using human microarrays. Transcription response of S. pneumoniae strain TIGR4 (serotype 4) in the presence of either mock- or viral-infected cells was analyzed by pneumococcal microarray. Significantly regulated genes were identified by both significance analysis of microarray (SAM) and a ≥ 2-fold change ratio cut-off. The adherence of S. pneumoniae to human pharyngeal cells was significantly augmented in the presence of RSV or HPIV3 infection. Global gene expression profiling of the host cells during infection with RSV or HPIV3 revealed increased transcription of carcinoembryonic antigen-related cell adhesion molecules (CEACAM1), CD47, fibronectin, interferon-stimulated genes and many other host cell adhesion molecules. Pneumococci increased transcription of several genes involved in adhesive functions (psaA, pilus islet), choline uptake and incorporation (lic operon), as well as transport and binding. Conclusions We have identified a core transcriptome that represents the basic machinery required for adherence of pneumococci to D562 cells infected or not infected with a virus. These bacterial genes and cell adhesion molecules can potentially be used to control pneumococcal adherence occurring secondary to a viral infection.
    BMC Genomics 06/2013; 14(1):378. DOI:10.1186/1471-2164-14-378 · 3.99 Impact Factor
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