The prevalence of the uncultivated bacterium TM7a in human subgingival plaque

Most bacteria are yet to be cultivated, and some uncultivated bacteria have been associated with human diseases. TM7, an uncultivated candidate division of bacteria, has been recently associated with periodontitis, a disease if left untreated causes tooth degradation and gum decay. A subgroup of TM7, known as TM7a, has been found in both human samples and activated wastewater. TM7a from these two locations are as high as 99.7% similar by 16S rRNA gene sequence analysis, leading researchers to believe both TM7a strains are very similar functionally. TM7a has been extensively studied in activated wastewater. However, little is known of its prevalence in the human oral cavity. This research surveyed for the first time the prevalence of TM7a in human subgingival plaque by using a quantitative PCR assay (qPCR) optimized for this study. The oral cavities of six healthy individuals were sampled. A total of 34 subgingival plaque samples were collected from 5 – 6 teeth per patient. It was determined by qPCR that TM7a was present in five of six (83%) patients and in 22 of 34 (64.7%) samples. The average abundance of TM7a in the human oral cavity was 3.36x107 ± 2.53x10 6 cells g-1 and comprised 2.88x10-1 % ± 2.16x10-1% – 1.00x10-3% ± 8.65x10-4% total bacteria. TM7a was also found to be significantly more abundant in plaques collected from the facial sites (p < 0.0005), and in posterior sites (p < 0.05). These data suggest that the prevalence of TM7a is dynamic in the human oral cavity and provides the basis for a potential large-scale study to quantify TM7a in a population