Elucidating the relationship between gut bacteria communities of raft-cultured Mytilus coruscus and water and sediment environments

Relationship between aquaculture environment and gut bacterial communities is crucial for the health of aquatic animals. However, scarce information is present about the composition, diversity, and function of potential gut bacteria and habitat environment in raft-cultured Mytilus coruscus. In this study, the interspecies interactions in the gut of M. coruscus and their culture environment (water and sediment) were investigated utilizing high-throughput sequencing. The research also assessed the relative contribution of potential pathogenic bacteria from the culture environment to M. coruscus. The study found that M. coruscus gut bacteria had considerably reduced alpha diversity compared to water and sediment (P < 0.05). Principal Coordinate Analysis (PCoA) demonstrated a clear differentiation between microbial communities in the intestines and those in the environment. SIMPER analysis indicated low similarity (7.22–9.03 %) in bacterial community composition between the gut and the environment but high similarity (89.48–90.24 %) in functional composition. The dominant bacterial composition in the gut was markedly different from that in the environment. Furthermore, potential pathogens in the gut also significantly differed from those in the environment, with a relatively low environmental contribution to gut pathogens of M. coruscus (3.46–7.79 %). Co-occurrence network analysis indicated that the gut bacterial network had fewer nodes, edges, and average degree than the environmental network. Still, the gut network had a higher proportion of positive connections. The PICRUSt2 results suggested that the relative abundance of functions related to metabolism in gut bacteria was lower than that of environmental bacteria. In contrast, the relative abundance of functions associated with the immune system and ecological adaptation was higher. These findings contribute to our understanding of the interaction between gut and environmental bacteria in M. coruscus as well as theoretical support for sustainable aquaculture management strategies for M. coruscus.