Composition and development of oral bacterial communities

Abstract

The oral bacterial microbiome encompasses approximately 700 commonly occurring phylotypes, approximately half of which can be present at any time in any individual. These bacteria are largely indigenous to the oral cavity; this limited habitat range suggests that interactions between the various phylotypes, and between the phylotypes and their environment, are crucial for their existence. Molecular cataloging has confirmed many basic observations on the composition of the oral microbiome that were formulated well before ribosomal RNA-based systematics, but the power and the scope of molecular taxonomy have resulted in the discovery of new phylotypes and, more importantly, have made possible a level of bacterial community analysis that was unachievable with classical methods. Bacterial community structure varies with location within the mouth, and changes in community structure are related to disease initiation and disease progression. Factors that influence the formation and the evolution of communities include selective adherence to epithelial or tooth surfaces, specific cell-to-cell binding as a driver of early community composition, and interorganismal interaction leading to alteration of the local environment, which represents the first step on the road to oral disease. A comprehensive understanding of how these factors interact to drive changes in the composition of the oral microbial community can lead to new strategies for the inhibition of periodontal diseases and dental caries.

Fig. 1

In-vitro biofilm model systems. (A) Flowcell for microscopy. (B) Commercial pneumatically driven microcapillary flow system (Fluxion Biosystems, www.fluxionbio.com). (C) Drip-flow reactor. (D) Multiwell plate with pins in lid. (E) Stirred fermenter with coupons held in rods. (F) Constant-depth film fermentor. Images C and E courtesy of Montana State University Center for Biofilm Engineering. Image F courtesy of Dr Jonathan Pratten, UCL Eastman Dental Institute. ePTFE.

Fig. 2

In-vivo oral-biofilm models. (A) foil-jacketed rod for retrieval of subgingival plaque, reprinted by permission from reference (74). (B) Retrievable enamel chip of the model of supragingival plaque.