By some estimates, the oxygen in one out of every five breaths you take comes from a bacterium called Prochlorococcus. Numbering in the trillion trillions, this tiny microbe is one of the most abundant organisms on Earth.
So when Prochlorococcus perform photosynthesis — using energy from the sun to release oxygen from a water molecule — that adds up to a lot of oxygen.
And yet this mass producer of an essential ingredient for life was unheard of until 20 years ago. Recently, scientists got together in Cambridge, Mass., to celebrate the discovery of the bacterium.