Marine Microbes Selfish With Sulfur

New light has been shed on how marine organisms prevent sulfur from being released into the atmosphere so that it instead can be used as a food source. The volatile sulfur compound dimethylsulfide (DMS) is an important source of cloud condensation nuclei and thus a key regulator of Earth's climate. DMS is produced by marine microorganisms from the abundant precursor dimethylsulfoniopropionate (DMSP). This pathway competes with another route that converts DMSP into a nonvolatile biosynthetic source of sulfur and carbon. Now, the demethylase enzyme responsible for converting DMSP into a nonvolatile food source for microbes has been identified by a team led by Mary Ann Moran of the University of Georgia, Athens (Science 2006, 314, 649). This enzyme is widely distributed among marine bacteria, but they may not be the only seafaring creatures that use DMSP. Many other marine microbes, including ubiquitous diatoms, also rely on DMSP as a source of carbon and sulfur, report Maria Vila-Costa and Rafel Simó of the Institute of Marine Sciences in Barcelona and coworkers (Science 2006, 314, 652).