Epiphytic common core bacteria in the microbiomes of co-located green (Ulva), brown (Saccharina, Gelidium) and red (Grateloupia) macroalgae

We collected specimens of <em>Ulva </em>sp. (green algae), <em>Saccharina </em>sp. (brown algae), <em>Grateloupia </em>sp., and <em>Gelidium </em>sp. (both red algae) during all four seasons from a coastal reef in Weihai, China, and analyzed their surface-colonizing bacteria in comparison to surrounding seawater and sediment controls. 16S rRNA amplicon sequencing, extensive plate cultivation, sequencing of selected strains, and sequencing of 23 metagenomes were performed in this study. Besides composition, we analyzed the potential of phycosphere bacteria to degrade algal polysaccharides and to produce bioactive secondary metabolites. This comprehensive dataset represents a significant stepping stone towards a better understanding of macroalgal phycosphere bacteria and paves the way to functional studies on representative strains.