Functional analysis of VicK kinase activity in Streptococcus mutans

OBJECTIVE: To investigate the regulatory function on physiology and virulence of VicK kinase activity in Streptococcus mutans. METHODS: PCR ligation mutagenesis was used to construct a vicK knock-out mutant, and kinase activity abolished VicK was expressed by a streptococcal vector in this vicK null mutant. Colony morphology, overnight culture, biofilm formation and gene expression involved in biofilm formation were analyzed. Delta VicK, strains harboring a complemented wild-type vicK, and a vector without insert were used as controls. RESULTS: Colonies of VicK(H217A) were smoother and more elevated than that of wild-type UA159 and complementary strain SMCVicK; cells from VicK(H217A) overnight culture coaggregated on the bottom of glass tubes; no obvious alteration was observed in VicK(H217A) biofilm; expressions of gbpB, ftf, gtfD were repressed while gtfB/C were up-regulated (P < 0.05). CONCLUSION: VicK kinase activity is important for maintaining normal growth, biofilm formation and expression of genes involved in biofilm formation in Streptococcus mutans.