Plesiomonas-mediated biotransformation of Magnolia officinalis compounds in largemouth bass (Micropterus salmoides): A microbial strategy to optimize Chinese herbal medicine efficacy

Chinese herbal medicines (CHM), employed for millennia in therapeutic applications, exhibit complex chemical compositions that frequently compromise the bioavailability of their bioactive constituents. Emerging evidence underscores the pivotal role of gut microbiota in modulating CHM efficacy. Despite this progress, the specific microbial taxa responsible for these interactions—particularly in aquatic species—remain poorly characterized, hindering the development of microbiota-based aquaculture strategies. In this study, we systematically investigated key gut microbes that influence the uptake of magnolol and honokiol by largemouth bass (Micropterus salmoides). We demonstrated that: (i) antibiotic-induced depletion of gut microbiota significantly diminished serum and hepatic concentrations of magnolol and honokiol (P < 0.05), confirming microbial dependency in their pharmacokinetics; (ii) combined 16S rRNA sequencing and machine learning identified Plesiomonas, a core bacterial genus, as the dominant taxon correlated with enhanced absorption; (iii) in vitro fermentation of Magnolia officinalis crude extract with P. shigelloides M2 elevated magnolol and honokiol yields by 31.6 % and 24.4 %, respectively, compared to sterile controls; and (iv) in vivo trials confirmed that fermented extracts enhanced peak blood concentrations of magnolol (7.60 mg/L vs. 5.85 mg/L) and honokiol (2.29 mg/L vs. 1.71 mg/L) compared to non-fermented extracts. These findings demonstrate that Plesiomonas plays a central role in the biotransformation of CHM within the intestinal microbiota of aquaculture species. This discovery provides practical avenues for optimizing CHM bioavailability in aquaculture through strategic manipulation of gut microbial communities.