Interaction between Streptococcus spp. and Veillonella tobetsuensis in the Early Stages of Oral Biofilm Formation

Abstract

Dental plaque is a multispecies oral biofilm, the development of which is initiated by adherence of the pioneerStreptococcusspp. OralVeillonellaspp., includingV. atypica,V. denticariosi,V. dispar,V. parvula,V. rogosae, andV. tobetsuensis, are known as early colonizers in oral biofilm formation. These species have been reported to coaggregate withStreptococcusspp. in a metabolic cooperation-dependent manner to form biofilms in human oral cavities, especially in the early stages of biofilm formation. However, in our previous study,Streptococcus gordoniishowed biofilm formation to the greatest extent in the presence ofV. tobetsuensis, without coaggregation between species. These results suggest thatV. tobetsuensisproduces signaling molecules that promote the proliferation ofS. gordoniiin biofilm formation. It is well known in many bacterial species that the quorum-sensing (QS) system regulates diverse functions such as biofilm formation. However, little is known about the QS system with autoinducers (AIs) with respect toVeillonella and Streptococcusspp. Recently, autoinducer 1 (AI-1) and AI-2 were detected and identified in the culture supernatants ofV. tobetsuensisas strong signaling molecules in biofilm formation withS. gordonii. In particular, the supernatant fromV. tobetsuensisshowed the highest AI-2 activity among 6 oralVeillonellaspecies, indicating that AIs, mainly AI-2, produced byV. tobetsuensismay be important factors and may facilitate biofilm formation ofS. gordonii. Clarifying the mechanism that underlies the QS system betweenS. gordoniiandV. tobetsuensismay lead to the development of novel methods for the prevention of oral infectious diseases caused by oral biofilms.