Discovery and characterization of algal enzymes synthesizing the biogeochemical sulfur-cycling agent dimethylsulfoniopropionate

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It is ironic that the tiniest oceanic microalgae have a huge global impact. More specificially, many taxa of micro- and macro- algae enzymatically synthesize dimethylsulfoniopropionate (DMSP), an important osmoregulatory compound, with multiple proposed functions. DMSP is broken down to the volatile compound dimethylsulfide (DMS), primarily by marine bacteria. DMS accounts for about half the global atmospheric sulfur budget, and influences global climate. As marine algae are the only source of oceanic DMSP and thus, the source of DMS, it is surprising that almost no research on DMSP synthesis has been done - not one enzyme is known! What are the molecular identities and structures of the enzymes catalyzing this major biogeochemical flux? Are they conserved in phylogenetically diverse algal species? Will gene identification predict an alga's capacity to make DMSP? I will use novel genome-enabled methods to answer these questions. My research program focuses on discovering the biochemical regulation of DMSP contents in algae. My short term goal is to disover the genes encoding the DMSP biosynthesis pathway enzymes using a combination of bacterial complementation assays, comparative genomics and classical protein purification methods. Purification of the native enzymes will enable gene identification technologies to discover the genes encoding DMSP metabolic enzymes. Purified native or recombinant DMSP enzymes will be characterized with respect to their biochemical structure, regulation, and kinetic behaviour. Identification of genes encoding DMSP metabolic enzymes will further our understanding of how widespread DMSP production is in 1) sequenced algal genomes by searching their genomes and 2) by using antibodies raised against purified enzymes in immunoblot analyses of those algae without sequenced genomes. These tools will also facilitate investigations of DMSP enzyme regulation under different conditions by monitoring transcript or protein expression level changes. Lastly, engineering of the algal DMSP metabolic pathway into other organisms may have commercial value.