Competence‐Stimulating Peptides in Oral Bacterial Signaling: Possible Implications in a Community Life

Abstract

The first studies focusing on the competence-stimulating peptide (CSP) system were prompted by investigations to understand competence development for natural transformation. CSP signals and regulatory pathways are found in most oral streptococci. The molecular mechanisms involved in CSP signaling have been described in more detail for Streptococcus pneumoniae than for other streptococci. The CSP autoinducing system is remarkably closely related to well-characterized bacteriocin autoinducing systems. Genetic competence and bacteriocin production appear to be closely linked in streptococci. It is possible, that the mechanisms involved in competence for genetic transformation are somehow uncoupled with the stress response to spectinomycin. The absence of one of the two components of the histidine kinase/response regulator ComDE impairs the increased biofilm formed in the presence of CSP, supporting the specificity of the response. The possible contribution of lysis and DNA binding to the CSP effect on biofilm formation is supported by the findings that mutants of Staphylococcus mutans deficient in the DNA binding and uptake machinery form less biofilm and that degradation of extracellular DNA reduces biofilm formation in streptococci. In the multicellular communities found in the oral cavity, natural interference with autoinducing signaling systems such as the CSP signaling pathway might be a natural scenario, depending on how the bacteria are structurally distributed in biofilms. Present efforts to sequence microbes commonly colonizing humans will certainly provide important tools to deepen our understanding of the interactions between microorganisms in complex communities, and the human responses to these communities.