Bacteria concentrated from 1 liter surface seawater were inoculated into a synthetic phycosphere microcosm experiment. After enriching in the lab for 8 days, the composition of these microbes were examined. Part I covers the 16S rRNA amplicon reads and two metagenome-assembled genomes (MAGs). Part II covers the raw metagenome reads from selected samples of synthetic phycospheres, 38 more MAGs and 11 genomes of pure isolates.