Dimethylsulfoniopropionate (DMSP) lyase activity in different strains of the symbiotic alga Symbiodinium microadriaticum

Abstract

Dimethylsulfoniopropionate (DMSP) lyases are responsible for the enzymatic conver- sion of the algal metabolite DMSP into dimethylsulfide (DMS) and other products. DMSP lyase poten- tial activity (DLA) was assayed in 5 cultured strains of Symbiodinium microadriaticum to investigate whether DLA was present and whether variations in DLA occurred among strains. S. microadri- aticum are important primary producers symbiotic with corals and other cnidarians. Four of the 5 tested S. microadriaticum strains were capable of performing enzymatic lysis of DMSP, and the lev- els of DLA varied significantly among the strains. Average DLA normalized to chlorophyll a (chl a) was significantly higher in strain CCMP 829 (5.3 ± 0.9 nmol DMS · min -1 · µg -1 ) compared with all other strains investigated. DLA was not detected in strain CCMP 830, suggesting that DMSP lyase may not be a universal enzyme in S. microadriaticum. DMSP levels also varied between strains, but there was no correlation between cellular DMSP and DLA. Additionally, our data indicate that in non-axenic S. microadriaticum strains, the bacterial contribution to DLA was not substantial in any of the algal cultures investigated. These results are supportive of the idea that S. microadriaticum contain DLA, that DMSP producers are not necessarily capable of DLA, and that, even within a spe- cies, DMSP and DLA levels vary significantly. These findings suggest important differences in the regulation of DMSP and DLA in S. microadriaticum, but the reasons for these differences remain to be elucidated.