Regulation of the Competence Pathway as a Novel Role Associated with a Streptococcal Bacteriocin

<jats:title>ABSTRACT</jats:title> <jats:p> The oral biofilm organism <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Streptococcus mutans</jats:named-content> must face numerous environmental stresses to survive in its natural habitat. Under specific stresses, <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">S. mutans</jats:named-content> expresses the competence-stimulating peptide (CSP) pheromone known to induce autolysis and facilitate the uptake and incorporation of exogenous DNA, a process called DNA transformation. We have previously demonstrated that the CSP-induced CipB bacteriocin (mutacin V) is a major factor involved in both cellular processes. Our objective in this work was to characterize the role of CipB bacteriocin during DNA transformation. Although other bacteriocin mutants were impaired in their ability to acquire DNA under CSP-induced conditions, the Δ <jats:italic>cipB</jats:italic> mutant was the only mutant showing a sharp decrease in transformation efficiency. The autolysis function of CipB bacteriocin does not participate in the DNA transformation process, as factors released via lysis of a subpopulation of cells did not contribute to the development of genetic competence in the surviving population. Moreover, CipB does not seem to participate in membrane depolarization to assist passage of DNA. Microarray-based expression profiling showed that under CSP-induced conditions, CipB regulated ∼130 genes, among which are the <jats:italic>comDE</jats:italic> locus and <jats:italic>comR</jats:italic> and <jats:italic>comX</jats:italic> genes, encoding critical factors that influence competency development in <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">S. mutans</jats:named-content> . We also discovered that the CipI protein conferring immunity to CipB-induced autolysis also prevented the transcriptional regulatory activity of CipB. Our data suggest that besides its role in cell lysis, the <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">S. mutans</jats:named-content> CipB bacteriocin also functions as a peptide regulator for the transcriptional control of the competence regulon. </jats:p>