The flesh of a healthy, living fish is considered sterile because the immune system prevents the growth of microorganisms. In this chapter, the authors present the current knowledge concerning the study and characterization of seafood microbiota, and then summarize the advances concerning biopreservation, a mild preservation method based on the use of selected protective flora. Biopreservation is a gentle food preservation technology that consists of preventing the development of undesirable microorganisms (pathogens or spoilers) by introducing into the product harmless microorganisms selected for their antimicrobial properties. A better understanding of bacterial interactions will therefore allow better control of its evolution during food preservation and more efficient biopreservation strategies to be proposed. Today, genome analysis of isolated bacteria or complex samples (metagenomics), as well as the numerous bioinformatics tools available, makes it possible to predict the presence of genes coding for molecules involved in bacterial interactions.