“Delicious seafood” on our table. Plankton and bacteria are important players in the marine environment as they lie in the base of the marine food chain. It is widely known that the energy needed by these primary producers are obtained from organic matters produced through photosysnthesis in the photic zone. However, in 2000, a new photoreceptor gene, named “proteorhodopsin”, was found from the genomic fragment of the SAR86 bacterial group. Subsequent researches revealed that proteorhodopsin gene is widely distributed among marine bacteria and archaea. Proteorhodopsin acts as a light-driven proton pump; capturing light energy and uses it to move protons across the membrane out of the cell. The resulting proton gradient is subsequently converted into chemical energy. At present, it is estimated that more than half of the prokaryotes inhabiting the ocean surface layer possess proteorhodopsin. Therefore, by estimating the amount of solar energy flowing into the marine ecosystem through proteorhodopsin is important.

Our group is working on elucidating the sequence diversity and spatiotemporal fluctuation of proteorhodopsin through metagenome and metatranscriptome analyses. We are also working on the evolution of proteorhodopsin gene and its physiological role using large-scale comparative genomics and culture experiments.