Metagenomic comparison of gut communities between hawksbills ( Eretmochelys imbricata ) and green sea turtles ( Chelonia mydas )

The gut microbiota is closely linked to host nutrition, immunity, and health. Here, metagenomic analysis was conducted to elucidate the taxonomic and functional diversity of gut communities from hawksbills and green sea turtles. In terms of diversity and abundance, the gut microbiota of herbivorous green sea turtles showed a higher bacterial diversity and richness than that of hawksbills. Firmicutes dominated in all groups; however, the phylum Proteobacteria showed a higher relative abundance in hawksbills. Several metabolic pathways displayed broad prevalence and high relative abundances in the two sea turtle populations. Antibiotic resistance genes (ARGs) responsible for resistance to glycopeptide and tetracycline were the most abundant in all samples. In ARGs, the subtype macB was the most abundant in the two different sea turtle populations; however, evgS, bcrA, and efrA were more abundant in the green sea turtles, while in the hawksbills, tetT and tetB(P) were more abundant. Among mobile genetic elements (MGEs), the abundance of 16 MGE types showed a significant difference between the two sea turtle populations. MGE type transposase and plasmid were the most abundant in the two sea turtle populations. Additionally, gene functions were enriched in carbohydrate esterases, glycoside hydrolases, and polysaccharide lyases in the green sea turtles, whereas genes related to glycosyltransferases and auxiliary activities were highly abundant in hawksbills. These metagenomic profiles provide further insights into the microbial diversities of the two types of sea turtles and provide valuable information for future conservation efforts.