The human salivary microbiome may play a role in diseases of the oral cavity, and it may interact with microbiomes from other parts of the human body, particularly the intestinal tract. Yet, little is known about normal variation in the salivary microbiome. Nasidze, et al’s study analyzed 14,115 partial (~500 bp) 16S ribosomal RNA sequences from 120 saliva samples from healthy humans in 12 worldwide locations. These sequences could be assigned to 101 known bacterial genera; of these, 39 were not previously reported from the human oral cavity. Phylogenetic analysis suggests that an additional 64 unknown genera are present. There is high diversity in the salivary microbiome within and between individuals, but little geographic structure. Overall, 13.5% of the total variance in the genera composition is due to differences among individuals, which is similar to the fraction of the total variance in neutral genetic markers that can be attributed to differences among human populations. When certain environmental variables were investigated, a significant association between the genetic distances among locations and the distance of each location from the equator was noted. Further characterizing the high diversity in the salivary microbiome will clarify its role in health and disease as well as its role in the identification of potentially informative species for studies of human population history.
(Source: Genome Research Web site, February 27, 2009)
