Novel Uncultured Bacterium Associated with Human Oral Plaque

Members of the uncultivated bacterial division TM7 have been found in a broad range of bacterial communities including soil, activated wastewater (sludge), humans, and other organisms.  In humans, TM7 has been associated with periodontitis – a disease that if untreated leads to gum loss and tooth decay. Within the TM7 division, a subgroup called TM7a has been identified in the human oral cavity, but also on the human skin and a range of environmental sites..  We aim to better understand the prevalence and diversity of TM7a in the human oral cavity.   Human subgingival plaque samples taken from six healthy adults with both healthy sites and sites with gingivitis, were analyzed for the presence of total TM7 as well as TM7a using culture-independent molecular techniques based on 16S ribosomal DNA (rDNA) gene sequence.  TM7a rDNA was found in all of our patients and accounted for 4.83% of all TM7 as determined by real-time quantitative PCR (qPCR).  Four new phylotypes of subgroup TM7a were identified, and members of TM7a were found to exhibit diplo-bacillus and filamentous morphology by Fluorescence in situ Hybridization (FISH).  Association of TM7a to human disease was not determined.