"We believe this is the first time bacterial horizontal gene transfer has been observed in eukaryotes at such scale," says senior author Igor Grigoriev of DOE JGI. "This study gets us closer to explaining the dramatic diversity across the genera of diatoms, morphologically, behaviorally, but we still haven't yet explained all the differences conferred by the genes contributed by the other taxa."
From plants, the diatom inherited photosynthesis, and from animals the production of urea. Bowler speculates that the diatom uses urea to store nitrogen, not to eliminate it like animals do, because nitrogen is a precious nutrient in the ocean. What's more, the tiny alga draws the best of both worldsit can convert fat into sugar, as well as sugar into fatextremely useful in times of nutrient shortage.
The team documented more than 300 genes sourced from bacteria and found in both types of diatoms, pointing to their ancient origin and suggesting novel mechanisms of managing nutrientsfor example utilization of organic carbon and nitrogenand detecting cues from their environment.
Diatoms, encapsulated by elaborate lacework-like shells made of glass, are only about one-third of a strand of hair in diameter. "The diatom genomes will help us to understand how they can make these structures at ambient temperatures and pressures, something that humans are not able to do. If we can learn how they do it, we could open up all kinds of new nanotechnologies, like for building miniature silicon chips or for biomedical applications," says Bowler.
Diatoms reside in fresh or salt water and can be divided into two camps, centrics and pennates. The centric Thalassiosira resemble a round "Camembert" cheese box (only much smaller) and pennates like Phaeodactylum look more like a cross between a boomerang and a narrow three-cornered hathence the species name, tricornutum. Not only is their shape and habitat dive
|Contact: David Gilbert|
DOE/Joint Genome Institute