Comprehensive Transcriptome Profiles of Streptococcus mutans UA159 Map Core Streptococcal Competence Genes

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Streptococcus mutans, a key player in dental caries, utilizes peptide pheromones like competence-stimulating peptides (CSPs) and SigX-inducing peptides (XIPs) to regulate natural genetic transformation.
• Competence development in S. mutans involves complex regulatory pathways, including response regulators like ComE and ComR, and the alternative sigma factor SigX, but the precise effector sets for each regulator remain poorly defined.

Purpose of the Study:

• To comprehensively define the regulons controlled by ComE, ComR, and SigX in Streptococcus mutans.
• To elucidate the early and late transcriptional responses to competence-stimulating peptides (CSPs).
• To identify a core set of pan-streptococcal competence genes.

Main Methods:

• Utilized high-resolution tiling arrays to map global gene expression changes during the early and late phases of the CSP response in S. mutans.
• Integrated new transcriptome data with previously published datasets.
• Compared transcriptome data across diverse streptococcal species to identify conserved competence genes.

Main Results:

• The early CSP response in S. mutans is limited to four bacteriocin-related loci, mediated by ComE.
• The late CSP response, dependent on comS expression, encompasses 29 loci, including genes for DNA uptake and recombination.
• Identified 4 ComE regulons, 2 ComR regulons, and 21 SigX regulons, with a core of 27 pan-streptococcal competence genes within the SigX regulon.

Conclusions:

• The study precisely defines the effector sets for ComE, ComR, and SigX regulons in S. mutans.
• CSP-mediated competence involves a restricted early response and a broader late response dependent on comS.
• A conserved set of competence genes across streptococcal species has been identified, providing insights into streptococcal social behavior and biofilm formation.