27 Genetics and Molecular Features of Bacterial Dimethylsulfoniopropionate (DMSP) and Dimethylsulfide (DMS)

Abstract: The transformations of dimethylsulfoniopropionate (DMSP; (CH 3 ) 2 S + CH 2 CH 2 COO ) by bacterioplankton play important roles in the global sulfur cycle. Thiscompound is produced in large quantities primarily for use as an osmolyte by marine algae.DMSP is a labile compound although the complete mineralization of DMSP is only a minorfate in the ocean. DMSP is the main precursor of dimethylsulfide (DMS; CH 3 -S-CH 3 ), aradiativelyactivetracegasthatcontributestoglobalclimateregulation.However,itisbelievedthat the main pathway for the transformation of DMSP involves an assimilation step inwhichDMSP sulfur is incorporated efficiently into cell biomass, leaving relatively little sulfuravailable for release as DMS. DMSP is rapidly turned over in the environment and thediversityofpathwaysforits transformationarelikelynot yetfully realized.Thischaptercoversrecent findings on the genetics of DMSP catabolism; their discoveries are changing our viewof the role of this compound in the World’s oceans. Although even less is known aboutbacterially-mediated transformations of DMS, the handful of genes that have been describedin a limited number of bacteria is also reviewed in this chapter.