MIT, CARLY SANKERThe cyanobacterium Prochlorococcus is arguably one of the most important organisms on the planet when it comes to supporting life. Hovering near the surface of the ocean, these microbes—a trillion trillion of them—produce half of the world’s oxygen. Given their abundance, results published today (April 24) in Science illustrating their astounding genomic diversity are not terribly surprising. But the study also uncovered genomic lineages, or “backbones,” that may have originated millions of years ago.
“Some of us did not believe that microbes are infinitely diverse,” despite a prevailing assumption, said Steve Giovannoni, who studies bacterioplankton at Oregon State University and who was not involved in the study. “That very high diversity is channeled into patterns, and we’re starting to see what those patterns look like.”
Sallie Chisholm, a microbial ecologist at MIT, has been studying Prochlorococcus for years. Previous genomic studies of the microbe had shown that individuals varied greatly from one another. Remarkably, within the Prochlorococcus strain in her current study—the so-called high-light–adapted Prochlorococcus—individuals share only about 1,450 “core” genes among the 2,000 genes in each genome. The rest are variable. (For comparison, humans share 95 percent of their genes with chimpanzees.) To dive deeper into Prochlorococcus diversity, ...
