Abstract
OBJECTIVE: Interspecies interactions of oral streptococci involve the production and excretion of antimicrobial compounds to compete successfully during colonization. Bacteriocin production by Streptococcus mutans and hydrogen peroxide (H2O2) production by Streptococcus sanguinis have been demonstrated as crucial for the clinical relevant antagonism between both species. A potential target of H2O2 is the cell-envelop of S. mutans. In the present study, the role of cell-envelop associated eukaryotic serine/threonine protein kinase (STPK) in S. mutans during interspecies competition has been investigated. DESIGN: Allelic replacement via homologous recombination of the STPK encoding gene with a kanamycin resistant determinant has been constructed. The mutant has been screened for the susceptibility towards cell-envelope stress. A previously developed spotting assay was used to simulate interspecies competition. RESULTS: The STPK(-) mutant showed an increased susceptibility towards envelop stress caused by H2O2 and was significantly more inhibited during interspecies competition assays. CONCLUSIONS: S. mutans is able to sense antimicrobial compounds excreted by competing species and can potentially adjust the cell-envelop towards an increased resistance.