Connecting microbial ecology to human fertility and reproduction: perspectives from the reproductive microbiomes of animals

In all vertebrates, reproduction occurs in the context of host-associated microbiomes, which are increasingly recognized for their contributions to reproductive success. Although host-associated microbiomes are species specific, synthesizing patterns in microbial ecology across human and animal taxa provides perspectives for understanding the factors that shape microbial communities and their contributions to reproduction. Additionally, the fertility and reproductive physiology of animals under human care-particularly endangered species-is often meticulously monitored to maximize reproductive opportunities. In this mini-review, we examine current knowledge on reproductive microbiomes in animals, focusing, when available, on the sparse literature for wildlife species. We suggest ways in which studying animal microbial ecology may advance human fertility and reproduction by focusing on 3 microbial communities-vaginal, milk, and seminal microbiomes-which represent a large portion of literature and have clear implications for reproductive health. We identify avenues of future research that will further strengthen the linkages between reproductive research in wildlife species and humans and provide potential guidelines for practical applications of microbiome science to human reproductive health.