Diversity and Morphology of Members of the Phylum “ Synergistetes ” in Periodontal Health and Disease

Abstract

ABSTRACT Members of the phylum “ Synergistetes ” have frequently been detected in the human oral cavity at sites of dental disease, but they have rarely been detected in studies of oral health. Only two oral “ Synergistetes ” taxa are cultivable. The aims of this study were to investigate the diversity of “ Synergistetes ” in the oral cavity, to establish whether “ Synergistetes ” taxa are more strongly associated with periodontitis than with oral health, and to visualize unculturable “ Synergistetes ” in situ. Sixty samples (saliva, dental plaque, and mucosal swabs) were collected from five subjects with periodontitis and five periodontally healthy controls. Using phylum-specific 16S rRNA gene primers, “ Synergistetes ” were identified by PCR, cloning, and sequencing of 48 clones per PCR-positive sample. Subgingival plaque samples were labeled with probes targeting rRNA of unculturable oral “ Synergistetes ” using fluorescent in situ hybridization (FISH). Analysis of 1,664 clones revealed 12 “ Synergistetes ” operational taxonomic units (OTUs) at the 99% sequence identity level, 5 of which were novel. “ Synergistetes ” OTU 4.2 was found in significantly more subjects with periodontitis than controls ( P = 0.048) and was more abundant in subgingival plaque at diseased sites than at healthy sites in subjects with periodontitis ( P = 0.019) or controls ( P = 0.019). FISH analysis revealed that unculturable oral “ Synergistetes ” cells were large curved bacilli. The human oral cavity harbors a diverse population of “ Synergistetes. ” “ Synergistetes ” OTU 4.2 is associated with periodontitis and may have a pathogenic role.