Disturbance ecology in the human oral ecosystem

Background/Question/Methods Complex microbial communities inhabit the subgingival crevices of the human oral cavity in both periodontal health and gum disease. Previous studies on oral ecology have shown that the distinction between health and disease is one of microbial community composition and relative abundances rather than the presence of particular microorganisms. However, the ecological forces that regulate these communities remain relatively unexplored. Professional teeth cleaning is one ecological force used to maintain and restore periodontal health. We examined the consequences of this disturbance on subgingival microbial communities in one healthy volunteer. We hypothesized that the community composition would (1) remain constant prior to disturbance, but shift directly following, and (2) display resiliency, returning to the pre-disturbance community over time. To test our hypothesis, we surveyed the composition of microbial communities from four subgingival sites before and after teeth cleaning. Dental plaque was sampled from each site over four time points. All visible microbial biomass was removed by cleaning, and we sampled the recovering plaque community over seven additional time points. Throughout the entire experiment, the subject was told to continue to follow a normal oral hygiene routine. Sample DNA was extracted, and the V3 region of the microbial ssRNA gene was amplified and sequenced. Results/Conclusions Unifrac Principle Components Analysis on sequences did not reveal clustering of communities by time of sampling from any of the four sites surveyed. Sequences were identified to genera using RDP Classifier. Preliminary data analysis suggests that the identities of dominant genera at each site remain stable, but their relative abundances fluctuate over time. This was true even among the four time points analyzed before the disturbance, indicating the community is relatively dynamic. Genera richness decreased immediately following disturbance and had not recovered within a month, although richness a week after the cleaning was greater than the hours immediately following it. Disturbance did not appreciably alter the communities' tendency toward variability in the relative abundances of genera present. Notably, however, the genus Fusobacterium, appeared to increase in abundance following disturbance in three of the four subgingival sites. This is interesting because Fusobacterium is thought to be a keystone taxon in the subgingival biofilm; it is has been shown to co-adhere to all other oral microbial taxa. Overall, however, professional teeth cleaning may be no more disruptive to healthy oral community dynamics than standard daily personal hygiene. Additional healthy and diseased mouths are currently being analyzed.