Identification of the streptococcal competence-pheromone receptor

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Genetic transformation in streptococci is induced by a secreted pheromone acting as a quorum-sensing signal.
• The competence factor (CF) coordinates the expression of late competence genes.
• Streptococcus pneumoniae utilizes competence-stimulating peptide (CSP) for this process.

Purpose of the Study:

• To identify and characterize the genes responsible for CSP production and pheromone response in Streptococcus gordonii.
• To elucidate the mechanism by which CSP regulates genetic competence.
• To determine the role of the ComD histidine kinase in CSP signaling.

Main Methods:

• Allele identification of the comC gene in Streptococcus gordonii strains.
• Nucleic acid sequencing of genes downstream of comC.
• Analysis of a two-component signal transduction system (ComD and ComE).
• Tracing CSP specificity to strain-specific comD alleles.

Main Results:

• Two alleles of the comC gene were identified in Streptococcus gordonii strains with distinct pheromones.
• Genes encoding a histidine kinase (ComD) and response regulator (ComE) were identified downstream of comC.
• Evidence suggests ComD acts downstream of CSP in competence regulation.
• Strain-specific alleles of comD correlate with CSP specificity, indicating ComD is the receptor.

Conclusions:

• The histidine kinase ComD functions as the receptor for the competence-stimulating peptide (CSP) in Streptococcus gordonii.
• This finding clarifies the molecular mechanism of quorum sensing and genetic competence regulation in streptococci.
• The study provides insights into the evolution of signal transduction pathways involved in bacterial communication.