Baboon vaginal microbiota: an overlooked aspect of primate physiology

The bacterial population of the vaginal canal is a primate infant’s first exposure to the microbial community inhabiting the outside world. Yet, little is known about this community and the effect it might have on the development and survival of the infant. Humans and Papio baboons share considerable anatomical and physiological similarities in their reproductive tracts. Accordingly, we might expect that the vaginal microbiota of baboons would be similar to that of humans. To characterize the vaginal microbiota of a nonhuman primate, we used denaturing gradient gel electrophoresis (DGGE) to evaluate variations in the vaginal microbiota of a group of 35 baboons housed in a facility where they shared the same diet and the same environmental conditions. We also used a 16S rRNA phylogenetic approach to assess the composition of the baboon vaginal microbiota in a subset of animals from this facility and from the wild. We found that despite the uniform environment, there were appreciable differences in the composition of the microbiota from one individual to another in the captive subjects. Our results also indicate that a simple swab test is sufficient for sampling of the vaginal microbiota in the field, a finding that should help make future, more detailed characterization of the microbiota of wild primates feasible. Previous human vaginal microbiota studies have shown that Firmicutes (mostly Lactobacillus spp.) predominate in the human vagina, with Actinobacteria (Gardnerella vaginalis) and Proteobacteria present in lower numbers. By contrast, Papio baboons harbored species not only of Firmicutes but also of Fusobacteria, Bacteroidetes and Spirochaetes phyla that are not normally abundant in humans. Moreover, the Firmicutes found in baboons were different from those found in humans, consisting mainly of clostridia rather than lactobacilli. A further level of difference was also seen within the same phylogenetic groups where baboon bacterial species clustered separately from those reported in humans. Results of our analyses imply that co-evolution of microbes and hosts cannot account for the major differences between the microbiota of baboons and that of humans, because divergences between the major genera were too ancient to have occurred since primates appeared. Instead, the primate vaginal tracts appear to have acquired discrete subsets of bacteria from the vast diversity of bacteria available in the environment and established a community responsive to and compatible with host species physiology