Streptococcal Antagonism in Oral Biofilms:Streptococcus sanguinisandStreptococcus gordoniiInterference withStreptococcus mutans

Abstract

ABSTRACTBiofilms are polymicrobial, with diverse bacterial species competing for limited space and nutrients. Under healthy conditions, the different species in biofilms maintain an ecological balance. This balance can be disturbed by environmental factors and interspecies interactions. These perturbations can enable dominant growth of certain species, leading to disease. To model clinically relevant interspecies antagonism, we studied three well-characterized and closely related oral species,Streptococcus gordonii, Streptococcus sanguinis, and cariogenicStreptococcus mutans. S. sanguinisandS. gordoniiused oxygen availability and the differential production of hydrogen peroxide (H2O2) to compete effectively againstS. mutans. Interspecies antagonism was influenced by glucose with reduced production of H2O2. Furthermore, aerobic conditions stimulated the competence system and the expression of the bacteriocin mutacin IV ofS. mutans, as well as the H2O2-dependent release of heterologous DNA from mixed cultures ofS. sanguinisandS. gordonii. These data provide new insights into ecological factors that determine the outcome of competition between pioneer colonizing oral streptococci and the survival mechanisms ofS. mutansin the oral biofilm.