Microbiota composition analysis of the colonic luminal content revealed no significant differences between male and female prepubescent mice. (A) Bacteriodetes and Firmicutes dominate the colon lumen in 2-week-old male and female pups. (B) Hierarchical clustering using weighted UniFrac as a distance measure of the male and female mouse pups revealed no clustering of the sexes. (C) RDA plots show microbiota differences based on litter origin, but (D) only marginal and not significant differences were found between male and female mice. Boxplot diagrams of the beta-diversity showed (E) a more distinct difference of the mice of litter 1 compared to litters 2 and 3 but (F) no significant differences between males and females. (G) OTU610 (classified as Syntrophococcus) was identified to being most uniquely associated and hence predictive for the male sex.