A dysbiosis in the intestinal microbiome plays a role in the pathogenesis of several immunological diseases. These diseases often show a gender bias, suggesting gender differences in immune responses and in the intestinal microbiome. We hypothesized that gender differences in immune responses are associated with gender differences in microbiota. We demonstrated mouse strain dependent gender differences in the intestinal microbiome. Interestingly, a cluster of colonic genes (related to humoral and cell-mediated immune responses) correlated oppositely with microbiota species abundant in B6 females and in BALB/c males. This suggests that with different genetic backgrounds, gender associated immune responses are differentially regulated by microbiota. The net result was the same, since both mouse strains showed similar gender induced differences in immune cell populations in the mesenteric lymph nodes. Therefore, host-microbe interactions might be more complicated than assumed, as bacterial-species adaptations might be highly dependent on the genetic make-up of the individual.