Host species and environment shape the gut microbiota of cohabiting marine bivalves

Abstract

Pacific oysters (Crassostrea gigas) and Mediterranean mussels (Mytilus galloprovincialis) are commercially important marine bivalves that frequently coexist and have overlapping feeding ecologies. Like other invertebrates, their gut microbiota is thought to play an important role in supporting their health and nutrition. Yet, little is known regarding the role of the host and environment in driving these communities. Here, bacterial assemblages were surveyed from seawater and gut aspirates of farmed C. gigas and co-occurring wild M. galloprovincialis in summer and winter using Illumina 16S rRNA gene sequencing. Unlike seawater, which was dominated by Proteobacteria, bivalve samples largely consisted of Tenericutes (Mollicutes), and accounted for >50% of the total OTU abundance. Despite large numbers of common (core) bacterial taxa, bivalve-specific species (OTUs) were also evident and predominantly associated with Mycoplasamataceae (notably Mycoplasma). An increase in diversity (though with varied taxonomic evenness) was observed in winter for both bivalves, and was associated with changes in the abundance of core and bivalve-specific taxa, including several representing host-associated and environmental (free-living or particle-diet associated) organisms. Our findings highlight the contribution of the environment and the host in defining the composition of the gut microbiota in cohabiting, intergeneric bivalve populations.

Bivalves and microbes: a mini-review of their relationship and potential implications for human health in a rapidly warming ocean

“…Bivalves harbor a diverse community of bacteria, including Proteobacteria, Firmicutes, and Bacteroidetes. Vibrionaceae, Pseudomonadaceae, and Flavobacteriaceae families (Leite et al, 2017;Akter et al, 2022). The structure of microbial communities in bivalves is highly variable, with different regions of the bivalve's body harboring distinct microbial communities.…”