Single-cell genomics of multiple uncultured stramenopiles reveals underestimated functional diversity across oceans.

Single-celled eukaryotes ( protists) are critical players in global biogeochemical cyclingof nutrients and energy in the oceans. While their roles as primary producersand grazers are well appreciated, other aspects of their life histories remain obscure due to challenges in culturing and sequencing their natural diversity. Here, we exploit single-cell genomics and metagenomicsdata from the circumglobal Tara Oceans expedition to analyze the genome content and apparent oceanic distribution of seven prevalent lineages of uncultured heterotrophicstramenopiles. Based on the available data, each sequenced genome or genotype appears to have a specific oceanic distribution, principally correlated with water temperature and depth. The genome content provides hypotheses for specialization in terms of cell motility, food spectra, and trophic stages, including the potential impact on their lifestyles of horizontal gene transferfrom prokaryotes. Our results support the idea that prominent heterotrophicmarine protistsperform diverse functions in ocean ecology.