Figure 2.

Schematic representation of the purported roles of Veillonella spp. in a commensal biofilm associated with health vs. a dysbiotic microbial community associated with periodontitis. Veillonella spp. are highly abundant within oral biofilms and besides their well-established bridging role in commensal biofilms (top panel), their alternative ecological role of as accessory pathogens has recently emerged (lower panel). Upper panel: Veillonella spp. have a key role in the colonization of mineralized (e.g., tooth enamel or cementum) and metal (e.g., dental implants) surfaces within the oral environment. Demonstrating symbiotic mutualism with commensal streptococci, they are early and abundant colonizers that also provide immune stimulation by their mildly potent LPS, which may be beneficial to the host for heightened immune surveillance that contributes to the establishment of a dynamic healthy equilibrium. Lower panel: In the inflammatory environment of the crevice in the presence of biofilms with high plaque biomass the microenvironmental conditions vary within the biofilm. Differences in lactate concentrations, the prime carbon source for Veillonella, and differences in oxygen availability may trigger virulent mechanisms in certain Veillonella strains, such as hemagglutinin-1 that provide adhesion positions for P. gingivalis or small molecules that support P. gingivalis early growth and colonization.