Gut Microbiota of Largemouth Bass in Response to Temperature and Temperature Stress

Abstract

The intestinal microbiota is crucial for maintaining host health, nutrient absorption, immune regulation, and pathogen resistance. This study investigates the effects of temperature and temperature stress on the intestinal microbiota of largemouth bass, an aquaculture species highly sensitive to temperature fluctuations. Fish were acclimated to 20°C and 35°C for one month, then divided into four groups subjected to stable or sudden temperature changes (T20-20°C, T20-35°C, T35-20°C, T35-35°C). After a 7-day exposure, intestinal microbiota was analyzed using 16S rRNA gene high-throughput sequencing. Results showed that temperature and temperature stress significantly altered microbiota composition and diversity. The relative abundances of Cetobacterium, Epulopiscium, Citrobacter, and Aeromonas were significantly increased in the cold stress (T35-20°C) group and heat stress (T20-35°C) group. In T35-35°C group, the relative abundance of the harmful bacteria Edwardsiella was significantly greater than that in the other groups (P < 0.05). The cold stress and the heat stress caused significant structural changes and reduced diversity. Temperature shifts from 35°C to 20°C increased bacterial network complexity, indicating enhanced cooperation for environmental adaptation. High heat stress (T35-35°C) reduced key species connectivity, destabilizing community structure. Positive bacterial interactions were more prevalent at low temperatures (T20-20°C). Temperature stress primarily influenced gut microbiota assembly through stochastic processes, reducing homogenous dispersal and increasing pathogenic bacteria sensitivity. These findings suggest that temperature stress disrupts intestinal microbiota homeostasis, impacting host health and aquaculture management. Understanding these effects is vital for optimizing aquaculture conditions and ensuring fish health and productivity.

Keywords: Intestinal microbiota, Largemouth bass, temperature, temperature stress