The symbiotic microbial communities of marine organisms play a key role in the physiology and adaptation of their host, constituting a central element of holobiont health. In bivalves, despite their economic importance and use as sentinel species for biomonitoring, the microbiome remains poorly understood.

This study aims to characterize the bacterial communities associated with the digestive gland, mantle, and gills of the Pacific oyster (Magallana gigas) and to assess their sensitivity to metal contaminants. Oysters were collected from six sites along the French coastline, and their bacteriomes were investigated by sequencing 16S rRNA amplicons (V3-V4). Heavy metal concentrations were measured in each organ by ICP-MS to explore the links between pollution and variations in the microbiome under natural conditions.