Bacterial chemotaxis and its potential role in marine dimethylsulfide production and biogeochemical sulfur cycling

Dimethylsulfide (DMS) gas constitutes 90% of biogenic sulfur emissions from oceans and is an important agent in climate regulation. DMS in seawater arises primarily via lyase degradation of dimethylsulfoniopropionate (DMSP), an osmolyte produced in high concentrations by some marine phytoplankton. After being induced to synthesize DMSP lyase, cells of a marine bacterium (Alcaligenes strain M3A) significantly reduce their rate of change in direction and tumbling frequency, and they are attracted to DMSP at levels similar to those occurring near senescing phytoplankton cells (10(-7)-10(-6) M). In contrast, genetically identical bacteria without lyase induction are not attracted to DMSP. Combined with lyase activity, bacterial chemotaxis to DMSP could increase the rate of DMS production and therefore play a critical role in biogeochemical sulfur cycling between dissolved organic matter in seawater and the atmosphere.