Changes of intestinal microbiota and metabolites in Huso dauricus under heat stress and their potential relationship with heat stress resistance

Ongoing global warming has intensified heat stress challenges for fish, especially cold-water species. This study focused on 4-month-old kaluga sturgeon ( Huso dauricus ), conducting heat stress experiments by raising the temperature from 19℃ to 25℃ at 1℃ per hour, with 19℃ as the control. Anatomical observations assessed heat stress injury in the gill, liver, and intestine, while pathological tissue sections evaluated intestinal injuries. Microbiome and metabolomics techniques explored the intestinal microbiota and metabolites' response to heat stress and their relationship with heat stress resistance. Results indicated that half of the sturgeons can adapt to heat stress without sustaining injury. Significant changes were observed in the intestinal microbiota due to heat stress, with a decrease in beneficial bacteria, such as Clostridium sensu stricto 1 and Candidatus Arthromitus , and an increase in the harmful bacterium Plesiomonas . Notably, this dysbiosis manifested differentially between groups: heat-resistant sturgeon were enriched in the beneficial Cetobacterium , whereas heat-stressed individuals harbored significantly more Plesiomonas . Changes in metabolite concentrations associated with energy supply, exemplified by Uridine diphosphate-N-acetylglucosamine, and with cell death pathways, as seen in gamma-Glutamylcysteine, were also noted in this study. The decline of Clostridium sensu stricto 1 and its related metabolite phenylacetic acid likely contributed to the rise in harmful bacteria and inflammatory injuries. Cetobacterium and its related metabolite lithocholyltaurine may enhance heat stress resistance. These findings offer a theoretical basis for improving fish heat stress resistance through microbiome regulation and suggest potential strategies for the aquaculture industry to address climate change. • Significant changes in intestinal microbiota structure of Huso dauricus under heat stress, with decreased beneficial and increased harmful bacteria. • Differential metabolites associated with energy supply, membrane structure, and cell death pathways may contribute to heat stress injury. • A strong correlation between intestinal microbiota composition and heat stress resistance in Huso dauricus highlights beneficial bacteria such as Cetobacterium . • Specific metabolites such as lithocholyltaurine may improve heat stress resistance, suggesting new microecological strategies in aquaculture.