Mating changes the genital microbiome in both sexes of the common bedbug Cimex lectularius across populations

Many bacteria live on host surfaces, in cells, and specific organ systems. Although gut microbiomes of many organisms are well-documented, the bacterial communities of reproductive organs, i.e. genital microbiomes, have received little attention. During mating, male and female genitalia interact and copulatory wounds can occur, providing an entrance for sexually transmitted microbes. Besides being potentially harmful to the host, invading microbes might interact with resident genital microbes and affect immunity. While sexual transmission of individual symbiont species is relatively well-understood, few studies have addressed how mating changes genital microbiomes. Here, we characterize male and female genital microbiomes in four different populations of the common bedbug Cimex lectularius and investigate mating-induced changes. We dissected reproductive organs from virgin and mated individuals to sequence their genital microbiomes. We show that mating changes genital microbiomes, suggesting bacteria are sexually transmitted. This raises the question how the hosts physiological and immunological mechanisms control mating-induced changes in their genital microbiomes. Also, genital microbiomes varied between populations and the sexes. This provides evidence for local and sex-specific adaptation of bacteria and hosts, again suggesting that bacteria might play an important role in shaping the evolution of reproductive traits. Coadaptation of genital microbiomes and reproductive traits might further lead to reproductive isolation between populations, giving reproductive ecology an important role in speciation. Future studies should investigate the transmission dynamics between the sexes and populations to uncover potential reproductive barriers.