METABOLISM OF DIMETHYLSULFONIOPROPIONATE AND GLYCINE BETAINE BY A MARINE BACTERIUM

The metabolism of the methylated osmolytes glycine betaine (GB) and dimethylsulfoniopropionate (DMSP) was studied in a bacterium (strain MD 14-50) isolated from a colony of the cyanobacterium Trichodesmium. MD 14-50 when grown on DMSP cleaved dimethylsulfide (DMS) from DMSP and oxidized acrylate. In contrast to DMSP, GB was metabolized by sequential N-demethylations. Low concentrations (100-mu-M) of DMSP or GB allowed the growth of MD 14-50 on glucose at higher salinities than in their absence. At elevated salinities, DMSP was accumulated intracellularly with less catabolism and DMS production. Thus, DMSP and GB were catabolized by different mechanisms but functioned interchangeably as osmolytes.