TURNOVER OF DIMETHYLSULFONIOPROPIONATE (DMSP) BY THE PURPLE SULFUR BACTERIUM THIOCAPSA-ROSEOPERSICINA M11 - ECOLOGICAL IMPLICATIONS

The use of dimethylsulfoniopropionate (DMSP) by the anoxygenic phototr ophic purple sulfur bacterium Thiocapsa roseopersicina M11 under diffe rent environmental conditions was studied. Under anoxic/light conditio ns DMSP cleavage occurred both at low and intermediate salinities but at different growth phases: at low salinity (5 parts per thousand S) D MSP cleavage was observed in the exponential growth phase, whereas at intermediate salinity (35 parts per thousand S) cleavage was not obser ved until the stationary phase was reached. At higher salinities DMSP accumulated intracellularly, prior to cleavage, suggesting usage as co mpatible solute. Circumstantial evidence suggests that under anoxic/li ght conditions acrylate, one of the DMSP cleavage products, was reduce d to propionate at the expense of intracellular sulfur oxidation, and subsequently used as carbon source. The addition of acrylate had an in hibitory effect on growth, the reduction of acrylate to propionate can thus play an additional role as a detoxification mechanism. Dimethyl sulfide (DMS), also a DMSP cleavage product, was not used under anoxic conditions. However, under oxic conditions both DMS and acrylate meta bolization resulted in protein production. DMSP lyase in cell suspensi ons was induced by acrylate and activity was enhanced in the light. Th e latter suggests that DMSP cleavage is an energy dependent process. T he potential anaerobic DMS production and aerobic consumption in T, ro seopersicina M11 is in agreement with previously observed diurnal DMS dynamics in coastal marine sediments, the natural habitat of this anox ygenic phototrophic bacterium. This is the first report in which a bac terium is described that is able to cleave DMSP with subsequent metabo lization of DMS. (C) 1998 Federation of European Microbiological Socie ties. Published by Elsevier Science B.V. All rights reserved.