In our lab, we have undertaken the characterization of the entire microbial community (bacteria, protists and viruses) in the hemolymph of the Pacific oysters using global analytical approaches (metabarcoding and shotgun sequencing). In order to determine the impact of the genetic background of the animals on the composition of the hemo-microbiota, we used oysters produced in hatchery (from the spawning until 1 years of development), with different genetic backgrounds and contrasting phenotypes, especially with respect to their susceptibilities to the phenomena of mortality rates.