show Abstracthide AbstractDark ocean microbial single-cell genomics. This is a reference genome for studying planktonic microorganisms from the ocean below 200 m. Genomes from predominant dark-ocean clades will improve interpretation of metagenomic, metatranscriptomic and metaproteomic data to better understand metabolic features and ecological roles of the microbial groups. We focus on microbes without representation in laboratory cultures or genome sequencing projects, as well as chemoautotrophic groups, which likely have a major impact on the global carbon cycle.