The Relationship between Microbiome Structure, Community Biomass and Inflammation in Chronic Periodontitis

A better understanding of the ecology of oral subgingival communities in relation to periodontal destruction and inflammation is required. This study evaluated whether increased inflammation, clinically measured as bleeding upon probing, is associated with a distinct microbiome. We characterized via 454-pyrosequencing of 16S rRNA gene libraries and quantitative PCR the subgingival microbiome of 22 subjects with chronic periodontitis, sampled at sites with similar periodontal destruction but differing by the presence of bleeding. Communities in periodontitis were also compared to those from 10 healthy individuals. In periodontitis, presence of bleeding was not associated with differences in alpha-diversity or community composition. Bleeding sites, however, had higher total bacterial load than those without bleeding. On the contrary, communities in health and periodontitis largely differed, with greater diversity and higher biomass in periodontitis and differences in community structure that resembled ecological succession, characterized by emergence of newly dominant community members in periodontitis without replacement of primary health-associated species. Thus, periodontitis communities showed increased proportions of taxa from the phyla Spirochaetes, Synergistetes, Firmicutes and Chloroflexi, while the proportion, but not the absolute levels, of Actinobacteria, particularly Actinomyces, were decreased in comparison to health. It was also found that higher bacterial load in periodontitis communities negatively correlated with the relative abundance of periodontitis-associated taxa, such as Tannerella and Johnsonella. It thus appears that inflammation is related to increased community biomass, which in turn, is the result of a delicate balance in the proportion of taxa within the highly diverse bacterial communities associated with periodontitis.