A Comparative Metagenomics Study on Gastrointestinal Microbiota in Amphibious Mudskippers and Other Vertebrate Animals

SIMPLE SUMMARY: Mudskippers are important ecological components of intertidal ecosystems. It was proposed that their guts may play significant roles for terrestrial adaptations of these amphibious fishes. However, their gastrointestinal components and differences in microbiota with other vertebrates were never reported. Here, we performed a comparative metagenome analysis among various vertebrate groups, classified by living habitats and feeding habits, and also acquired microbial gene catalogs of five common fish species. Our findings confirmed the dominant microbial genera in each vertebrate group, as well as bacteriocin-related genes in the five common fish species, for discussion of their relationships with fish pathogenic diseases. Our big data will support in-depth investigations into potential roles of gastrointestinal microbiota to hosts and related applications in aquaculture practices. ABSTRACT: Gut microbiomes in various fish species were widely investigated with the rapid development of next-generation sequencing technologies. However, little is known about gastrointestinal (GI) microbial communities in mudskippers, a representative group of marine amphibious fishes, and their comparisons with other vertebrate animals from different habitats. Here, we performed a comprehensive analysis on microbial composition in five representative vertebrate groups (including amphibious mudskippers, marine and freshwater aquatic fishes, amphibians, and terrestrial animals) via operational taxonomic unit (OTU) survey and obtained a microbial gene catalog of five common fish species by metagenome sequencing. We observed that Cyanobacteria, Proteobacteria, Firmicutes, Bacteroidetes, and Fusobacteria were the most substantial bacteria in mudskippers. Differential variances in composition patterns of GI microbiota among the vertebrate groups were determined, although Proteobacteria and Firmicutes were the shared phyla with high abundance. In addition, Cetobacterium and Photobacterium were the most abundant genera in core OTUs of these examined omnivores, carnivores, and herbivores. Our metagenomic analysis also showed significant differences between the representative blue-spotted mudskipper and grass carp (both are herbivorous fishes) in microbes at the phylum and class levels and functional gene terms. Moreover, several bacteriocin-related genes were identified in the five common fishes, suggesting their potential contributions to pathogen resistance. In summary, our present work not only sheds new light on the correlation of GI microbiota composition with living habitats and feeding habits of the hosts, but also provides valuable bacterial genetic resources for healthy growth of aquaculture fishes.