Dimethyl sulfide mediates microbial predator-prey interactions between zooplankton and algae in the ocean

Phytoplankton are key components of the oceanic carbon and sulfur cycles. During bloom events, some species can emit large amounts of the organosulfur volatile dimethyl sulfide (DMS) into the ocean, and consequently the atmosphere, where it can modulate aerosol formation and affect climate. In aquatic environments, DMS plays an important role as a chemical signal mediating diverse trophic interactions. Yet, its role in microbial predator-prey interactions remains elusive with contradicting evidence for its role in either algal chemical defense or in the chemoattraction of grazers to prey cells. Here, we investigated the signaling role of DMS during zooplankton-algae interactions by genetic and biochemical manipulation of the algal DMS-generating enzyme dimethylsulfoniopropionate lyase (DL) in the bloom-forming alga Emiliania huxleyi. We inhibited DL activity in E. huxleyi cells in-vivo using the selective DL-inhibitor 2-bromo-3-(dimethylsulfonio)-propionate (Br-DMSP), and overexpressed ...