What is "prochlorococcus"

Prochlorococcus is a genus of very small (0.6 µm) marine cyanobacteria with an unusual pigmentation ( chlorophyll b). These bacteria belong to the photosynthetic picoplankton and are probably the most abundant photosynthetic organism on Earth. Microbes of the genus Prochlorococcus are among the major primary producers in the ocean, responsible for a large percentage of the photosynthetic production of oxygen. Analysis of the genome sequences of 12 Prochlorococcus strains show that 1100 genes are common to all strains, and the average genome size is about 2000 genes. In contrast, eukaryotic algae have over 10,000 genes.