ENUMERATION OF BACTERIA WHICH CLEAVE OR DEMETHYLATE DIMETHYLSULFONIOPROPIONATE IN THE CARIBBEAN SEA

Populations of dimethylsulfoniopropionate (DMSP) degrading bacteria were enumerated in Caribbean Sea waters using Most Probable Number (MPN) methodology. DMSP and 3-methiolpropionate (MMPA), an intermediate in the demethylation pathway of DMSP degradation, were used as enrichment substrates. Two metabolically distinct populations were obtained: DMSP cleavers, which produced dimethyl sulfide (DMS) from DMSP, and demethylators of DMSP, which produced 3-mercaptopropionate (MPA) and/or methanethiol (MSH) from DMSP or MMPA. Demethylating populations were distinct from DMS producers and formed 5 to 66 % of total DMSP degraders. DMSP utilizers comprized about 10 % of the total bacteria (MPNs on glucose-acetate) indicating the potential of DMSP as a carbon source for bacteria in the euphotic zone.