Dimethylsulfoniopropionate (DMSP) assimilation by

A variety of bacterial phylogenetic groups assimilate dimethylsulfoniopropionate (DMSP), an organic sulfur compound that can satisfy most of the sulfur (S) demand of bacteria in the surface waters of the ocean. Marine Synechococcus are capable of utilizing some forms of dissolved organic matter, but it is unknown if Synechococcus also assimilate DMSP. To better understand the role of Synechococcus in the flux of DMSP, we used microautora-diography to follow the assimilation of 35S-DMSP and 35S-methanethiol, an intermediate in DMSP assimilation, by Synechococcus in the surface waters of the Gulf of Mexico and the northwest Atlantic Ocean. About 85 % of Synechococcus cells assimilated S from DMSP and methanethiol in these environments, and Synechococcus assim-ilated more DMSP per cell than other bacteria. On average, Synechococcus accounted for roughly 20 % of prokary-otic DMSP assimilation in the northwest Atlantic and the Gulf of Mexico. Tests with axenic cultures of Synecho-coccus revealed that two phycoerythrin-containing strains (WH8102 and WH7803) were capable of DMSP transport, although these strains did not produce dimethylsulfide (DMS). These data indicate that DMSP could provide a significant amount of S to Synechococcus and that Synechococcus are important consumers of DMSP in the ocean. Dimethylsulfoniopropionate (DMSP) can play an impor-tant role in marine food webs and in the regulation of globa