From the tropics to the poles, from the sea surface to hundreds of feet below, the world’s oceans are teeming with one of the tiniest of organisms: a type of bacteria called Prochlorococcus, which despite their minute size are collectively responsible for a sizable portion of the oceans’ oxygen production. But the remarkable ability of these diminutive organisms to diversify and adapt to such profoundly different environments has remained something of a mystery. Now, new research reveals that these tiny bacteria exchange genetic information with one another, even when widely…