SAR11 are the most abundant plankton in the world's oceans. They are also a massive source of two sulfur gases that play important roles in the Earth's atmosphere.

Many types of gaseous fumes emerge from the ocean, such as formaldehyde, acetone and methanol, but the researchers behind a new study say they were very surprised that the cells under scrutiny produced both dimethylsulfide - DMS - which we recognize as the smell of the sea, and methanethiol, the smell of which makes us think of leaking gas lines. 

The
dimethylsulfide
 is made by a newly discovered gene, according to the study, and it was completely unexpected. And while the author's knew the cells could make methanethiol internally, they did not expect it to be released in large quantities. 

"In the atmosphere dimethylsulfide oxidizes to sulfuric acid, which some scientists think can seed cloud formation and alter heating of the Earth," said Steve Giovannoni, a distinguished professor of microbiology in the College of Science at Oregon State University, and corresponding author of the study.  

What is most interesting, the scientists said, is that the newly discovered metabolic circuit is hardwired into cells. Normally, cells turn genes on and off, as they are needed, but the newly discovered circuits for sulfur gas production by SAR11 are on all the time.

"That doesn't mean the cells are always producing the gases," said Giovannoni. "But they are always ready if algae in the surrounding water make DMSP, a compound that the SAR11 cells harvest for energy, releasing sulfur gases as waste products."