Diversity of bacterial dimethylsulfoniopropionate degradation genes in surface seawater of Arctic Kongsfjorden

Dimethylsulfoniopropionate (DMSP), which is the major source of organic sulfur in the world’s oceans, plays a significant role in the global sulfur cycle. This compound is rapidly degraded by marine bacteria either by cleavage to dimethylsulfide (DMS) or demethylation to 3-methylmercaptopropionate (MMPA). The diversity of genes encoding bacterial demethylation (dmdA) and DMS production (dddL and dddP) were measured in Arctic Kongsfjorden. Both dmdA and dddL genes were detected in all stations along a transect from the outer to the inner fjord, while dddP gene was only found in the outer and middle parts of the fjord. The dmdA gene was completely confined to the Roseobacter clade, while the dddL gene was confined to the genus Sulfitobacter. Although the dddP gene pool was also dominated by homologs from the Roseobacter clade, there were a few dddP genes showing close relationships to both Alphaproteobacter and Gammaproteobacter. The results of this study suggest that the Roseobacter clade may play an important role in DMSP catabolism via both demethylation and cleavage pathways in surface waters of Kongsfjorden during summer.