Phototaxis of the dominant marine pico-eukaryote Micromonas sp.: from population to single cell

摘要: Micromonas commoda (previously pusilla, a unicellular photosynthetic picoeukaryote globally dominant in marine ecosystems, has previously been qualified as being strongly phototactic. To date, no detailed quantitative or qualitative description of this behaviour reported, nor have thorough studies its motility undertaken. This primary producer only qualitatively described utilizing run-and-tumble motion, but such strategy is incompatible with morphology comprising one propelling flagellum. Moreover, it still unclear to how sp. detects light direction due the lack dedicated eyespot; organism essentially blind. Here we first perform population-scale phototactic experiments show that actively responds wide range wavelengths and intensities. These population responses are well accounted for within simple drift-diffusion framework. Based on single-cell tracking experiments, then detail thoroughly sp.9s which resembles run-and-reverse styles motion commonly observed prokaryotes name stop-run reverse. The associated peculiar microscopic changes upon photo-stimulation finally integrating those into jump-diffusion simulations appears produce drifts quantitatively compatible obtained experimentally at level.