Phylogenomic fingerprinting of tempo and functions of horizontal gene transfer within ochrophytes

Significance

The ochrophytes are an ancient and important group of eukaryotic algae, including diatoms, the most important photosynthesisers in the modern ocean, and a wide range of other species. Throughout their history, ochrophytes have exchanged genes with bacteria and eukaryotes through horizontal gene transfer (HGT), diversifying their cell biology. Here, we profile thousands of phylogenetic trees, showing that HGTs from bacteria contribute particularly to the recent evolution of diatoms, occurring more frequently than HGTs from eukaryotes and, potentially, more frequently in diatoms than other ochrophytes. Using experimental and computational techniques, we show that bacterial HGTs predominantly impact the diatom secreted proteome, which may contribute to the striking evolutionary success of diatoms.