Figure 3.

The core subgingival microbiome in health and periodontitis. OTUs that are part of the core microbiome were first defined as those present in at least 50% of subjects in both the healthy and periodontitis groups (gray), in at least 50% of healthy subjects (green) or in at least 50% of subjects with periodontitis (red). Prevalence and relative abundance data were used for further filtering. OTUs in gray represent the core subgingval OTUs, present at equal prevalence and relative abundance in health and periodontitis. OTUs in green represent the core health-associated species, appearing at increased prevalence and relative abundance in health compared to disease. OTUs in red represent the core periodontitis-associated species, present at increased prevalence and relative abundance in periodontitis compared to health. Inner circles labeled with 1, contain highly prevalent and highly abundant OTUs, that is, present in at least 2/3 of samples from each group (core, health or periodontitis) and numerically dominant with a mean relative abundance of ⩾2% of total sequences. Middle circles labeled with 2 contain OTUs highly prevalent but present in low abundance, that is present in at least 2/3 of samples from the specific group but with a mean relative abundance of <2% of total sequences. Outer circles labeled with 3 contain OTUs moderately prevalent and present in low abundance, that is OTUs present in 1/2 to 2/3 of samples from each group and with a mean relative abundance of <2% of total sequences.