Symbiotic microbial communities associated with marine organisms may contribute to the biology and the local adaptation of their host, playing a crucial role in the health of the holobiont. The role of the microbiome of bivalves remains poorly understood despite their high economic value and use as sentinel species to biomonitor water quality. In this study, we used 16S (V3-V4) rRNA amplicon sequencing to investigate the resident bacterial communities associated with the digestive gland, the mantle and the gills of Pacific oysters. We analysed oysters collected from six sites along the French coastline to investigate whether chemical stressors can shape the oyster bacteriome in natural conditions. The resident bacteriome of oysters was dominated by the phyla Proteobacteria, Spirochaetota, Firmicutes and Actinobacteriota with some differences between organs. Chemical analysis revealed differences in trace metal concentration among sites and organs. Statistical analysis showed strong positive or negative correlations between the concentration in some metals and bacterial diversity (ASVs abundance). We identified 316 ASVs associated with As, Cr, Cu, Mn and Zn concentrations in digestive glands, 99 ASVs associated with Ni concentrations in gills, and 116 ASVs associated with Cu concentrations in the mantle. Metal contamination mostly affected members of the core microbiota of oysters such as genera Colwellia and Psychrobacter , evidencing the crucial role of marine pollutants, particularly trace metals, as key parameters of the interactions between hosts and their bacterial partners • Trace metals accumulation differs between sites and organs in oysters. • Bacterial communities are also different between sites and organs. • Some bacterial taxa are strongly associated with trace metal contamination. • Cu, Cr, Mn, Ni, Zn and As were key covariates of bacteriome structure in oysters’ organs. • Genera Colwellia and Psychrobacter are particularly linked to metal content.
Roger et al. (Thu,) studied this question.