Regulation of Bacteriocin Production in Streptococcus mutans by the Quorum-Sensing System Required for Development of Genetic Competence

Abstract

In Streptococcus mutans, competence for genetic transformation and biofilm formation are dependent on the two-component signal transduction system ComDE together with the inducer peptide pheromone competencestimulating peptide (CSP) (encoded by comC). Here, it is shown that the same system is also required for expression of the nlmAB genes, which encode a two-peptide nonlantibiotic bacteriocin. Expression from a transcriptional nlmAB-lacZ fusion was highest at high cell density and was increased up to 60-fold following addition of CSP, but it was abolished when the comDE genes were interrupted. Two more genes, encoding another putative bacteriocin and a putative bacteriocin immunity protein, were also regulated by this system. The regions upstream of these genes and of two further putative bacteriocin-encoding genes and a gene encoding a putative bacteriocin immunity protein contained a conserved 9-bp repeat element just upstream of the transcription start, which suggests that expression of these genes is also dependent on the ComCDE regulatory system. Mutations in the repeat element of the nlmAB promoter region led to a decrease in CSP-dependent expression of nlmAB-lacZ. In agreement with these results, a comDE mutant and mutants unable to synthesize or export CSP did not produce bacteriocins. It is speculated that, at high cell density, bacteriocin production is induced to liberate DNA from competing streptococci.

Global transcriptional analysis of acid-inducible genes in Streptococcus mutans: multiple two-component systems involved in acid adaptation

“…The results showed that, similar to the microarray data, comYA and comX were indeed downregulated at pH 5.5, but comE and the two bacteriocin-related genes were upregulated at this pH (Table 2). These results are surprising, since the ComCDE quorum sensing system in S. mutans is known to control both genetic competence and bacteriocin production (Li et al, 2001a;van der Ploeg, 2005). One may expect the same impact when the ComCDE signal pathway is activated.…”

Antimicrobial peptide GH12 suppresses cariogenic virulence factors of Streptococcus mutans

“…comD encodes the histidine kinase receptor to response to competence-stimulating peptide (CSP), and comE encodes an intracellular response regulator to mediate expressions of downstream genes. Activated ComE enables the production of mutacin Ⅳ and Ⅴ, as well as genetic competence [49]. Significant downregulation of comDE was also observed in the 1/2 MIC group, and downregulation of comDE by 1/2 MIC of GH12 suppresses regulation of genetic competence and intra-species cell–cell communication.…”

The AlternativeTranslational Profile That Underlies the Immune-Evasive State of Persistence in Chlamydiaceae Exploits Differential Tryptophan Contents of the Protein Repertoire

“…If the host immune surveillance system has not yet activated IDO (with its consequence of Trp depletion), then sufficient Trp nutrients will exist to support the full expression of the competent state. Cells in the competent state may confer certain temporary growth advantages, such as the ability to utilize DNA as a source of nutrients such as carbon, nitrogen, and phosphorus (e.g., as speculated by van der Ploeg [130]). Yet competence is at the same time a fragile physiological state.…”