Variation in the intestinal bacterial community composition under different water temperature culture conditions in largemouth bass (Micropterus salmoides).

Aims: This study aimed to investigate the impact of temperature on the intestinal microbiota of largemouth bass using 16S rRNA gene amplicon sequencing, focusing on the under-explored role of abiotic factors in shaping the gut microbial community.

Methods and results: Five water temperature groups (20.0 ± 0.2 °C, 25.0 ± 0.2 °C, 28.0 ± 0.2 °C, 31.0 ± 0.2 °C, and 35.0 ± 0.2 °C) were established, each with three replicates. Significant variations in intestinal bacterial community composition were observed across these conditions. Elevated temperatures (31.0 ± 0.2 °C and 35.0 ± 0.2 °C) led to an increase in opportunistic pathogens such as OTU180 Vibrio and OTU2015 Vogesella (P < 0.05). Species correlation network analysis showed a shift towards more positive relationships among intestinal microbes at higher temperatures (P < 0.05). Ecological process analysis highlighted a greater role of ecological drift in microbial community structure at 31.0 ± 0.2 °C and 35.0 ± 0.2 °C (P < 0.05).

Conclusions: The study suggests that higher temperatures may predispose largemouth bass to opportunistic pathogens by altering their intestinal microbiota. Effective water temperature management is crucial for largemouth bass aquaculture to mitigate pathogen risks and maintain a balanced intestinal microbiota. This research provides critical insights into the temperature-microbiota relationship and offers practical recommendations for aquaculture practices.