Graduate Student Literature Review: Potential mechanisms of interaction between bacteria and the reproductive tract of dairy cattle.

Although the presence of bacteria has been characterized throughout the reproductive tracts of multiple species, how these bacteria may interact with the host has yet to be described. Previous reviews have described how pathogenic bacteria interact with the reproductive tract to cause infections such as metritis. This review aimed to summarize the knowledge related to pathogenic and nonpathogenic bacteria in various locations of the bovine reproductive tract and the possible mechanisms underlying host-microbe interactions during gametogenesis and early pregnancy. Lactic acid bacteria such as Lactobacillus seem to be beneficial in multiple areas of the reproductive tract: they have been associated with increased oocyte quality when in follicular fluid and secrete reactive oxygen species that are beneficial during placental angiogenesis. However, other bacteria, including Enterococcus, Staphylococcus, and Streptococcus, may modulate T helper cells that inhibit maternal recognition of pregnancy. Available data on the reproductive microbiome focus on variations in microbial communities and their associations with reproductive performance. However, research on these host-microbiome interactions may provide more insight on how bacteria affect fertility.