Making “Scents” of the Baboon Vaginal Microbiome

Research on the evolutionary role microbiomes play in their animal hosts has received a great deal of attention over the past few decades. Most of this work has focused on the complex and mutually beneficial relationships between the gut microbiome and animal host. To better understand how these relationships affect animal fitness, research must expand beyond the gut, such as to the reproductive microbiome. The microbial communities in the reproductive tract of animals can play a significant role in host fitness by mediating fertility and pregnancy outcomes and may even play a role in communicating social and reproductive information about their hosts by metabolizing compounds used by the host to communicate olfactorily. This hypothesis was first posited in the 70s as the ‘fermentation hypothesis', yet to date few studies have tested its applicability. To address this gap, my PhD leveraged longitudinal and cross-sectional data on captive and wild primate vaginal odor and microbiomes. I used a solvent-less extraction thermal desorption technique and performed 16S rRNA sequencing to measure the chemical profiles and bacterial compositions of captive and wild primate vaginas, respectively. I then tested whether the chemical composition of vaginal odors and the microbiome were connected, whether they both varied over the ovarian cycle, and whether odors conveyed information about the hosts’ reproductive state by performing behavioral bioassays to measure the response of captive primates to fertile and non-fertile odors. I found that the vaginal odor and microbiome were correlated and co-varied over the ovarian cycle in the wild, but not in captivity. I then showed that captive primates differentiated between fertile and non-fertile odors. Additionally, I found that the vaginal odor and microbiome were individually unique in our longitudinal dataset, and that captive primates differentiated between the odors of individual females. My work tentatively confirms that the fermentation hypothesis can be applied to primate communication, while demonstrating that captivity may disrupt the ability of females to convey information relative to fitness. This work also demonstrates the importance of using longitudinal datasets, as individual chemical profiles and microbiomes were highly personalized, which must be accounted for when testing whether host-associated microbiomes affect animal fitness. Overall, my work demonstrates the need to expand beyond the gut to additional bodysites to better understand the fitness consequences of host-associated microbiomes.