Analysis of microbiota in cultures of the green microalga <i>Tetraselmis suecica</i>

Bacteria associated with microalgae strongly affect algal biomass and derived product yield and quality. Nevertheless, only a few studies have addressed the detailed phylogenetic characterization of bacterial communities associated with microalgae. In this study, the phycospheric bacterial communities associated with different <i>Tetraselmis suecica</i> F&amp;M-M33 cultures, a green marine microalga with several industrial applications, were analysed using a metagenomic approach. The <i>T. suecica</i> F&amp;M-M33 cultures used originated from the same ancestral microalgal non-axenic culture but were physically and geographically separated for years and maintained under different growing conditions. Despite the different history of the cultures, a ‘core’ bacterial community was identified, accounting for 70% of the total bacterial community and formed by at least 13 families. Among the ‘core’ operational taxonomic units (OTUs), 24 different genera were identified. Nevertheless, there was a high variability in the relative proportions of the taxa forming the ‘core’ community, indicating that the growing conditions and/or external contamination influence the relative abundance of these microorganisms. Our study allowed the identification of persistent taxa that may be used to deepen the knowledge of the complex relationship between <i>T. suecica</i> and its associated bacteria.