A grant has been awarded to Drs. Mary Ann Moran, William B. Whitman, and Anne O. Summers of the University of Georgia, and Ronald P. Kiene of the University of South Alabama to investigate the microbes mediating a key step in the marine sulfur cycle. Dimethylsulfoniopropionate (DMSP) is an abundant organic sulfur compound synthesized by marine algae. When marine bacteria degrade DMSP, they can produce dimethylsulfide (DMS), a volatile compound that is the largest natural source of organic sulfur to the atmosphere. However there are competing bacterial degradation pathways for DMSP, the end products of which play only a minor role in ocean-atmosphere flux of organic sulfur. The genetic basis for these competing degradation pathways and how they are regulated within marine bacterial cells is unknown. Further, it is not understood how environmental conditions in the ocean influence the pathways by which marine bacteria degrade DMSP. In this project, analysis of the genomic sequence of a DMSP-degrading marine bacterium (Silicibacter pomeroyi) will be used in conjunction with molecular biology approaches to identify metabolic and regulatory genes involved in DMSP degradation. Identified genes will be used to retrieve genes with the same function from uncultured and potentially novel marine bacteria from surface waters of coastal and open ocean environments. An important goal of the project is to develop molecular tools for studying the marine bacteria that degrade DMSP in seawater, including how they interact with one another and the environment.
