Differences and inter-seasonal variations in gut microbial communities of different predatory fish in Chaohu Lake, China

Although fish gut microorganisms are closely related to fish growth and development, nutrient absorption, physiological status, and disease control, there is still a lack of knowledge about the gut microbial communities of wild fish in the natural state. In this study, we systematically and comprehensively investigated the changes of gut microbial communities of seven different species of wild fish in Chaohu Lake, which is closed to fishing and has low water exchange, over four consecutive seasons. It was found that the microbial community structure of different fish species with different dietary preferences showed significant differences according to the grouping, and overall, the gut microbial communities of fish in different seasons also showed significant differences. In addition, the fish gut microbial community in Chaohu Lake was mainly composed of Firmicutes, Proteobacteria(Gamma), Proteobacteria(Alpha), Actinobacteriota, and Cyanobacteria at the phylum level of classification, while Aeromonas, Cetobacterium, Clostridium sensu stricto 1, Romboutsia, and Pseudomonas dominated at the genus level of classification. The analysis of the co-occurrence network of fish gut microorganisms showed that C. auratus, C. carpio, and C. brachygnathus have more complex and robust gut microbial network structures than H. molitrix, C. alburnus, C. ectenes taihuensis, and A. nobilis,. Some microbial groups, such as Clostridium sensu stricto 1, Romboutsia, and Pseudomonas, are both dominant and keystone microbial groups in the fish gut microbial network structure, and these microorganisms are involved in the formation of modular communities that may play very important functional roles in various aspects of fish growth. Our study provides a new approach to the study of wild fish gut microbes in natural environments under controlled conditions, because it not only reveals comprehensive and more realistic information about the gut microbial communities of different wild fish living in natural environments with less water exchange and more constant waters, but also answers some questions about the microbial ecology of fish by using such environments.