The bacterial microbiota in the oral mucosa of rural Amerindians

The oral microbiota plays an important role in buccal health and in diseases such as periodontitis and meningitis. The study of the human oral bacteria has so far focused on subjects from Western societies, while little is known about subjects from isolated communities. This work determined the composition of the oral mucosa microbiota from six Amazon Amerindians, and tested a sample preservation alternative to freezing. Paired oral swabs were taken from six adults of Guahibo ethnicity living in the community of Platanillal, Amazonas State, Venezuela. Replicate swabs were preserved in liquid nitrogen and in Aware Messenger fluid (Calypte). Buccal DNA was extracted, and the V2 region of the 16S rRNA gene was amplified and pyrosequenced. A total of 17 214 oral bacterial sequences were obtained from the six subjects; these were binned into 1034 OTUs from 10 phyla, 30 families and 51 genera. The oral mucosa was highly dominated by four phyla: Firmicutes (mostly the genera Streptococcus and Veillonella), Proteobacteria (mostly Neisseria), Bacterioidetes (Prevotella) and Actinobacteria (Micrococcineae). Although the microbiota were similar at the phylum level, the Amerindians shared only 62% of the families and 23% of the genera with non-Amerindians from previous studies, and had a lower richness of genera (51 vs 177 reported in non-Amerindians). The Amerindians carried unidentified members of the phyla Bacteroidetes, Firmicutes and Proteobacteria and their microbiota included soil bacteria Gp1 (Acidobacteriaceae) and Xylanibacter (Prevotellaceae), and the rare genus Phocoenobacter (Pasteurellaceae). Preserving buccal swabs in the Aware Messenger oral fluid collection device substantially altered the bacterial composition in comparison to freezing, and therefore this method cannot be used to preserve samples for the study of microbial communities.