An analysis of the bacterial community in and around scleractinian corals of Phu Quoc Island, Vietnam

Corals harbor a myriad of microorganisms, many of which play a beneficial role for their host. To date, many of these microbes have not been identified, and information is also lacking on their origin, in particular their potential presence in the surrounding seawater or sediment. In this study, we used 16S rRNA gene sequencing to investigate the bacterial communities associated with three genera of scleractinian coral (Acropora, Lobophyllia and Porites) of the coast of Phu Quoc Island in Vietnam. We surveyed the bacterial communities on the mucous layer of these corals, as well as in the water column and the surface sediment in their vicinity, which we considered as five biotopes: Acropora, Lobophyllia, Porites, water column, and sediment. Overall, we identified 29 phyla, 50 classes, 114 orders, 254 families, and 402 genera across all samples. Proteobacteria were dominant in most of the biotopes, while Desulfobacterota and Bacteroidota were mainly found in the sediment. Bacteriome analysis based on amplicon sequence variants (ASVs) suggested that five genera (Algicola, Algicola bacteriolytica, Alteromonas, Catenococcus, and Vibrio) were the core bacteria in the three coral biotopes, but there were no shared ASVs across all five biotopes investigated. Additionally, linear discriminant analysis revealed that 23 biomarkers differed significantly across the five biotopes, with coral biotopes having the highest diversity of bacterial taxa (15 biomarkers), followed by seawater (4 biomarkers) and sediment biotopes (4 biomarkers). These findings highlight that the composition of the coral bacteriome is significantly different from that of nearby seawater and sediment samples, and that the composition may be specific to the coral host.