Conserved Pheromone Production, Response and Degradation by .

, a bacterium with high cariogenic potential, coordinates competence for natural transformation and bacteriocin production via the XIP and CSP pheromones. CSP is effective in inducing bacteriocin responses but not competence in chemically defined media (CDM). This is in contrast to XIP, which is a strong inducer of competence in CDM but can also stimulate bacteriocin genes as a late response. Interconnections between the pathways activated by the two pheromones have been characterized in certain detail in UA159, but it is mostly unknown whether such findings are representative for the species. In this study, we used bioassays based on luciferase reporters for the bacteriocin gene and the alternative sigma factor to investigate various isolates for production and response to CSP and XIP pheromones in CDM. Similar to UA159, endogenous CSP was undetectable in the culture supernatants of all tested strains. During optimization of the bioassay using the reporter, we discovered that the activity of exogenous CSP used as a standard was reduced over time during growth. Using a FRET-CSP reporter peptide, we found that UA159 was able to degrade CSP, and that such activity was not significantly different in isogenic mutants with deletion of the protease gene or the competence genes , , and . CSP cleavage was also detected in all the wild type strains, indicating that this is a conserved feature in . For the XIP pheromone, endogenous production was observed in the supernatants of all 34 tested strains at peak concentrations in culture supernatants that varied between 200 and 26000 nM. Transformation in the presence of exogenous XIP was detected in all but one of the isolates. The efficiency of transformation varied, however, among the different strains, and for those with the highest transformation rates, endogenous XIP peak concentrations in the supernatants were above 2000 nM XIP. We conclude that XIP production and inducing effect on transformation, as well as the ability to degrade CSP, are conserved functions among different isolates. Understanding the functionality and conservation of pheromone systems in may lead to novel strategies to prevent or treat unbalances in oral microbiomes that may favor diseases.