Prochlorococcus

Prochlorococcus is a genus of marine cyanobacteria whose cells, at about half a micrometer across, are among the smallest photosynthetic organisms on Earth, and it is probably the most abundant photosynthetic organism on the planet, responsible for an estimated thirteen to forty eight percent of global oxygen production. It thrives across tropical and subtropical oceans between forty degrees north and forty degrees south, with more than one hundred thousand cells in a single milliliter of surface seawater, dominating nutrient-poor waters from the surface down to roughly one hundred fifty meters. It was discovered in 1986 by Sallie W. Chisholm and colleagues at MIT using flow cytometry in the Sargasso Sea, with the first laboratory culture isolated in 1988; Chisholm received the Crafoord Prize in 2019 for the discovery.