Interspecies Interactions Promote Multispecies Communities

Abstract

Multispecies communities, not a collection of single-species colonies, compose human oral biofilms. The human oral microbiome is the most intensely studied and, perhaps, the best-characterized ecosystem in humans, but the organization of these species into multispecies communities at any point in time remains poorly understood. Genomic inquiry of community members will enable a fuller vision of each member’s metabolic contribution to the community. A central contributor to colonization of oral bacteria in biofilms is the universal ability of these species to attach to a surface: to teeth or to epithelial cell surfaces or to the bacterial surface of an already attached cell. Cells suspended in saliva are unable to multiply within a typical between-swallows interval due to the rapid salivary flow. Thus, adherence is essential before multispecies communities can develop and colonize the surface. Following coadherence and coaggregation, attached cells grow, as evidenced by incorporation of radiolabeled nucleosides and by cell division planes observed in the biofilms of intraoral mounted pieces of enamel or glass. Evidence-based two-species and three-species biofilms contribute in understanding species succession leading to a crossroad between health and disease in dental plaque biofilms. Virulence mechanisms exhibited by red complex periodontal pathogens are discussed in an inspired review of the interplay between pathogenic and commensal bacteria in disrupting host homeostasis. It is recognized that multispecies communities respond differently than pure cultures to antimicrobials.