"You'll consume about 2 liters (just over a half gallon) of oxygen in the time it takes you to read this post. About 20 percent of that oxygen comes from photosynthesis by marine diatoms — the most important little organisms that most people have never heard of."
Andrew Alverson, biologist and diatoms expert at the University of Arkansas in Fayetteville, has a piece about diatom genomes at Live Science. Check out the fantastic image gallery of these important, tiny life forms.