Cross-feeding-based rational design of a probiotic combination of <i>Bacterides xylanisolvens</i> and <i>Clostridium butyricum</i> therapy for metabolic diseases

The human gut microbiota has gained interest as an environmental factor that contributes to health or disease. The development of next-generation live biotherapeutic products (LBPs) is a promising strategy to modulate the gut microbiota and improve human health. In this study, we identified a novel cross-feeding interaction between <i>Bacteroides xylanisolvens</i> and <i>Clostridium butyricum</i> and developed their combination into a novel LBP for treating metabolic syndrome. Using <i>in-silico</i> analysis and <i>in vitro</i> experiments, we demonstrated that <i>B. xylanisolvens</i> supported the growth and butyrate production of <i>C. butyricum</i> by supplying folate, while <i>C. butyricum</i> reciprocated by providing pABA for folate biosynthesis. Animal gavage experiments showed that the two-strain combination LBP exhibited superior therapeutic efficacy against metabolic disorders in high-fat diet-induced obese (DIO) mice compared to either single-strain treatment. Further omics-based analyses revealed that the single-strain treatments exhibited distinct taxonomic preferences in modulating the gut microbiota, whereas the combination LBP achieved more balanced modulation to preserve taxonomic diversity to a greater extent, thereby enhancing the stability and resilience of the gut microbiome. Moreover, the two-strain combinations more effectively restored gut microbial functions by reducing disease-associated pathways and opportunistic pathogen abundance. This work demonstrates the development of new LBP therapy for metabolic diseases from cross-feeding microbial pairs which exerted better self-stability and robust efficacy in complex intestinal environments compared to conventional single-strain LBPs.