Bacillus maritimus strain N2 promotes testicular molecular signatures in Bohai Black cattle by remodeling the rumen microbiota-host metabolic axis

Probiotics have attracted significant attention as a potential strategy to improved testicular molecular signatures relevant to reproduction in ruminants. In this study, Bohai Black cattle were used as a model to systematically elucidate the mechanisms by which Bacillus maritimus strain N2 positively modulates testicular transcriptomic and metabolic signatures through multi-omics techniques. The study found that feeding N2 to the cattle specifically enriched the rumen with Adlercreutzia bacteria, which have anti-inflammatory potential, and markedly reduced levels of pro-oxidant toxins, such as phenolic derivatives, in the host circulatory system, accompanied by an increase in the antioxidant metabolite quercetin. Integrated analysis indicated that these metabolic changes were closely associated with a testicular gene co-expression module enriched for oxidative phosphorylation. Ultimately, N2 intervention significantly enhanced the expression of key protein markers involved in steroid synthesis, germ cell development, and blood-testis barrier integrity in the testes. This study is the first to depict a cross-organ regulatory axis of probiotics through 'enriching rumen Adlercreutzia-remodeling host metabolic profile-activating testicular energy and barrier programs,' providing an important mechanistic example for a deeper understanding of gut-testis interactions.