Effects of fecal microbiota transplantation and metabolite supplementation on the gut-brain-gonad axis of Trachemys scripta elegans

Background: Previous studies have shown that higher salinity affects the spermatogonial stem cells (SSC) of T. s. elegans through the gut-brain-gonad axis, and gut GABA content of T. s. elegans increased and showed a significant correlation with SSC differentiation. Results: To explore the effect of intestinal flora on SSC, fecal microbiota transplantation (FMT) experiments were carried out. The intestinal contents of the 10‰ group (S10) under salt stress for six months were prepared into bacterial suspensions. The normal saline group (NS), the antibiotic + normal saline group (ANS), and the antibiotic + FMT group were set up and fed with fresh water for two months. The results showed that the gut microbiota composition, the expressions of reproductive related genes in brain and self-renewal and differentiation genes and testicular steroid synthesis genes in testicle of the FMT group all decreased compared to the ANS group, which was similar to the S10 group, indicating that intestinal microbiota plays a vital role in SSC function. To furthur explore the effect of gut metabolites on the function of SSC, control group (CK) and a 100 mg/kg GABA supplementation group were established and fed with fresh water for two months. The results showed that the gut microbiota changed, the expression of reproductive related genes in brain and testicle SSC differentiation decreased in the GABA group compared to the CK group, which was similar to the S10 group. Conclusions: This study clarifies the molecular mechanism by which a high-salinity environment inhibits the self-renewal and differentiation of SSC through the gut-brain-gonad axis by reshaping the intestinal flora and metabolites. The results provide a new perspective for analyzing invasive species' environmental adaptation strategies and propose a new targeted prevention and control path for the invasion of T. s. elegans .