Additive attenuation of virulence and cariogenic potential of Streptococcus mutans by simultaneous inactivation of the ComCDE quorum-sensing system and HK/RR11 two-component regulatory system

Abstract

The genome of Streptococcus mutans harbours 13 two-component signal transduction systems (TCSTSs). Of these, a peptide-mediated quorum-sensing system, ComCDE, and the HK/RR11 two-component system are well known to regulate several virulence-associated traits in in vitro experiments, including genetic competence, bacteriocin production, biofilm formation and stress responses. In this study, we investigated the hypothesis that inactivation of ComCDE, HK/RR11 or both systems would attenuate the virulence and cariogenicity of S. mutans. The results showed that simultaneous inactivation of both signal transduction systems additively attenuated S. mutans virulence and cariogenicity, since inactivation of either of these systems alone did not result in the same degree of effect. The double deletion mutant SMcde-hk11 was defective in genetic competence, had a reduced acid production, was unable to grow at pH 5.0 and formed an abnormal biofilm with reduced biomass. Animal studies showed that this mutant had reduced capabilities for oral colonization, succession and initiation of dental caries. A competitive index (CI) analysis using a mixed-infection animal model revealed that all the mutants, particularly SMcde-hk11, had reduced fitness in their ecological niches and were unable to compete with the wild-type strain for persistence in dental biofilms. The evidence from this study suggests that the ComCDE and HK/RR11 signal transduction systems can be considered to be novel targets for the development of strategies in the prevention and treatment of S. mutans infections.

The BceABRS Four-Component System Regulates the Bacitracin-Induced Cell Envelope Stress Response in Streptococcus mutans

“…The transformants grown on THYE plus erythromycin (10 g/ml) were genetically confirmed by a PCR strategy using primers P1 and P4 in combination with the primers designed for the erm r cassette (18,22). The presence of the Erm marker with predicted sizes of the flanking region in the mutant but not in the parent strain indicated successful deletion and replacement by the erm r cassette at the desired locus (22). The same strategy was also used to construct the rest of the gene deletion mutants.…”

StreptococcusAdherence and Colonization

“…6). In addition, the TCSS HK/RR11 (Table 3) controls biofilm architecture, and HK11 may act as a second receptor for CSP (355). CSP-mediated communication has also been shown to be important for biofilm formation in 432 NOBBS ET AL.…”

Stress Physiology of Lactic Acid Bacteria

“…Notwithstanding this, the number of investigations that directly associate S. mutans acid stress survival pathways with caries formation is still rather limited. In addition to the aforementioned in vivo studies with Clp chaperones/proteases and the Spx oxidative stress regulators, which are also important for acid stress survival (304,346), several caries studies were carried out using S. mutans strains lacking different TCS regulators or the PknB serine/threonine kinase (539)(540)(541)). An S. mutans fabM mutant did not produce unsaturated membrane fatty acids, was extremely acid sensitive, was poorly transmitted from host to host, and exhibited fewer and less severe carious lesions than those caused by the parent strain (542,543).…”