Intriguing Functionality of the Production and Conversion of DMSP in Phaeocystis SP

Abstract

In many areas of the ocean the distribution and conversion of dimethylsulfoniopropionate (DMSP) may to a high degree be influenced by the activity of the Prymnesiophyte alga Phaeocystis sp.: it not only produces DMSP in large amounts, but is also able to convert it enzymatically into dimethylsulfide (DMS) and acrylate. Characteristic properties of DMSP-lyase in Phaeocystis sp. indicate that the enzyme is different from lyase enzymes in other organisms studied. During a spring bloom in Dutch coastal waters, DMSP-lyase activity was strongly correlated with Phaeocystis sp. cell numbers and potentially capable of producing DMS in excess of abiotic loss factors. In Phaeocystis sp. cells, DMSP makes an important contribution to the intracellular osmotic potential, with concentrations of approximately 150 mM. Upon salinity shocks, however, short term regulation of its internal levels was not observed. Although a slow adaptation of the DMSP production in Phaeocystis sp. cells may affect intracellular concentrations on a long term, it is concluded that DMSP-lyase is not involved in the short term osmotic adaptation of the cell. DMSP is a structural component of the cell, being produced continuously in the light as well as in the dark. DMSP-lyase activity facilitates the release of DMSP from the cell, with some intriguing beneficial effects.