Role of Streptococcus mutans eukaryotic-type serine/threonine protein kinase in interspecies interactions with Streptococcus sanguinis

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 hydrogenperoxide (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.

Keywords: Interspecies interactions, Streptococcus mutans, Streptococcus sanguinis, Oral biofilm