Comprehensive Transcriptome Profiles ofStreptococcus mutansUA159 Map Core Streptococcal Competence Genes.
InStreptococcus mutans, an oral colonizer associated with dental caries, development of competence for natural genetic transformation is triggered by either of two types of peptide pheromones, competence-stimulating peptides (CSPs) (18 amino acids [aa]) or SigX-inducing peptides (XIPs) (7 aa). Competence induced by CSP is a late response to the pheromone that requires the response regulator ComE and the XIP-encoding genecomS. XIP binds to ComR to allow expression of the alternative sigma factor SigX and the effector genes it controls. While these regulatory links are established, the precise set of effectors controlled by each regulator is poorly defined. To improve the definition of all three regulons, we used a high-resolution tiling array to map global changes in gene expression in the early and late phases of the CSP response. The early phase of the CSP response was limited to increased gene expression at four loci associated with bacteriocin production and immunity. In the late phase, upregulated regions expanded to a total of 29 loci, includingcomSand genes required for DNA uptake and recombination. The results indicate that the entire late response to CSP depends on the expression ofcomSand that the immediate transcriptional response to CSP, mediated by ComE, is restricted to just four bacteriocin-related loci. Comparison of the new data with published transcriptome data permitted the identification of all of the operons in each regulon: 4 for ComE, 2 for ComR, and 21 for SigX. Finally, a core set of 27 panstreptococcal competence genes was identified within the SigX regulon by comparison of transcriptome data from diverse streptococcal species.IMPORTANCES. mutanshas the hard surfaces of the oral cavity as its natural habitat, where it depends on its ability to form biofilms in order to survive. The comprehensive identification ofS. mutansregulons activated in response to peptide pheromones provides an important basis for understanding howS. mutanscan transition from individual to social behavior. Our study placed 27 of the 29 transcripts activated during competence within three major regulons and revealed a core set of 27 panstreptococcal competence-activated genes within the SigX regulon.
Department of Oral Biology, Faculty of Dentistry, University of Oslo, Oslo, Norway.
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Khan
Department of Oral Biology, Faculty of Dentistry, University of Oslo, Oslo, Norway.
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Rukke
Department of Oral Biology, Faculty of Dentistry, University of Oslo, Oslo, Norway.
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Høvik
Department of Oral Biology, Faculty of Dentistry, University of Oslo, Oslo, Norway.
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Åmdal
The Forsyth Institute, Cambridge, Massachusetts, USA.
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Chen
Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois, USA.
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Morrison
Department of Oral Biology, Faculty of Dentistry, University of Oslo, Oslo, Norway.
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Petersen
CSP; Streptococcus; XIP; genetic competence; natural transformation systems; pheromone; quorum sensing