Multiple Streptococcus mutans Genes Are Involved in Biofilm Formation

Abstract

Streptococcus mutans has been strongly implicated as the principal etiological agent in dental caries. One of the important virulence properties of these organisms is their ability to form biofilms known as dental plaque on tooth surfaces. Since the roles of sucrose and glucosyltransferases in S. mutans biofilm formation have been well documented, we focused our attention on sucrose-independent factors. We have initially identified several mutants that appear to be defective in biofilm formation on abiotic surfaces by an insertional inactivation mutagenesis strategy applied to S. mutans. A total of 27 biofilm-defective mutants were isolated and analyzed in this study. From these mutants, three genes were identified. One of the mutants was defective in the Bacillus subtilis lytR homologue. Another of the biofilm-defective mutants isolated was a yulF homologue, which encodes a hypothetical protein of B. subtilis whose function in biofilm formation is unknown. The vast majority of the mutants were defective in the comB gene required for competence. We therefore have constructed and examined comACDE null mutants. These mutants were also found to be attenuated in biofilm formation. Biofilm formation by several other regulatory gene mutants were also characterized using an in vitro biofilm-forming assay. These results suggest that competence genes as well as the sgp and dgk genes may play important roles in S. mutans biofilm formation.

Quantitative analyses of Streptococcus mutans biofilms with quartz crystal microbalance, microjet impingement and confocal microscopy

“…The order of adhesiveness of S. mutans to the different surfaces is polystyrene > HA > glass. This finding is also consistent with previous observations (Yoshida & Kuramitsu, 2002). COMSTAT analysis of S. mutans biofilm structures grown with indicated sucrose concentrations.…”

“…The most widely used is the microtiter plate assay for measuring the amount of biofilm formation (O'Toole & Kolter, 1998). Although not a means of direct measurement, this method has been used by a number of laboratories for screening mutants that affect biofilm formation (O'Toole & Kolter, 1998;Yoshida & Kuramitsu, 2002;Friedman & Kolter, 2004). Although semi-quantitative and easy to perform, the microtiter plate assay does not provide information on the kinetics of biofilm formation or the architecture of the biofilm.…”

Kinase activity of the dgk gene product is involved in the virulence of Streptococcus mutans

“…Considering the results of the animal experiment, that the dgk mutation did not effectively affect fissure caries formation, but drastically reduced smooth-surface caries formation, decreased sucrosedependent colonization of the dgk mutant may contribute to a decrease in S. mutans infection levels. However, in vitro experiments revealed that the dgk mutation did not affect sucrose-dependent biofilm formation at all, while a slight effect on glucose-dependent (without sucrose) biofilm formation was observed (data not shown), consistent with the result of the previous study (Yoshida & Kuramitsu, 2002). These results suggest that the Dgk may be not involved in sucrose-dependent colonization of S. mutans in vitro.…”

Antimicrobial and anti-biofilm activities of Lactobacillus kefiranofaciens DD2 against oral pathogens

“…Streptococci are also known to aggregate to form oral biofilms; for instance, S. mutans rapidly increases biofilm thickness by producing surface-associated and biofilm regulatory proteins [7,9,10]. As such, reducing the size of cariogenic bacterial populations and suppressing biofilm formation are essential strategies for the prevention of oral diseases [11].…”