Bacterial dimethylsulfoniopropionate production in marine sediments

Dimethylsulfoniopropionate (DMSP) is an abundant sulfurous anti-stress compound that plays major roles in nutrient and sulfur cycling, climate regulation and signalling to higher organisms. It was thought that only marine eukaryotes produce significant amounts of DMSP, but this is not the case. We have shown that some marine alphaproteobacteria also make DMSP at similar concentrations to those reported for DMSP-producing marine eukaryotes. We have identified the first gene, mmtN, for DMSP synthesis in any organism. This key gene exists in many other DMSP-producing marine bacteria and is present in marine metagenome datasets. These bacteria also lyse DMSP, having DMSP lyase ddd genes that generate the climate-cooling gas dimethylsulfide (DMS). Our proposal will use molecular genetics to identify other enzymes of the bacterial DMSP synthesis pathway. The regulation of both DMSP synthesis and lysis in bacteria will be studied to determine the environmental conditions that affect DMSP and DMS production - for the first time in a single organism at a genetic level. Geochemical and molecular approaches will be combined to study the diversity and expression of functional mmtN genes in the environment. We will also study the diversity of DMSP producing bacteria and estimate their importance in DMSP production.