the metacommunity of the fish associated microbiome in different body habitats

Skin, gill and gastrointestinal tract are the main mucosal surfaces and immune barriers, and these mucosal habitats are colonized by complex microbial communities, which interact with host immune systems and regulate nutrient metabolism. Metacommunity theory integrates the local- and regional-scale dynamics to explore symbiotic community composition patterns across space, holistically understand host microbiome ecology. To explore the diversity and change as body weight increased of fish associated microbial communities and their potential assemble mechanism, we applied the metacommunity theory to explore the Siganus fuscescens associated microbial communities from different body habitats (e.g., skin, gill, stomach and hindgut) and their relationships with host body weight. Results reveal that the β-diversity but not α-diversity of fish-associated microbial communities from each habitat significantly increased as body weight increased. Also, opportunistic pathogens and probiotics (e.g., Pseudomongs, Methylobacterium) were widely distributed in different body habitats of S. fuscescens, and many digestive bacteria (e.g., Clostridium) and several key carbohydrate metabolic pathways were abundant in the hindgut, suggesting that these microbes play important roles in host health by balancing microbial community composition in each habitat. Both diversity patterns and ecological processes suggested that habitat separation could alter the microbial community composition and structure by reducing dispersal. This integrative work enhances our mechanistic understanding of host-associated bacterial communities within the metacommunity ecology framework and has important implications for host-associated meta-ecosystem.