The groundbreaking results of Fujiwara-san's master’s research, now a first-year PhD student, have been published in Nature! Despite facing challenges with experiments at times, the study ultimately evolved into a significant international collaboration, culminating in this remarkable achievement. Congratulations, Fujiwara-san! 🎉

Almost all life on Earth relies on solar energy for survival. However, only a limited number of organisms can convert sunlight into usable chemical energy. While photosynthetic organisms, such as plants and some microbes using chlorophyll, are well-known for this role, a substantial number of aquatic microbes are also capable of converting sunlight into chemical energy using microbial rhodopsins—light-absorbing proteins bound to retinal pigments. These two distinct light-harvesting systems serve as vital gateways for introducing solar energy into aquatic ecosystems.

In this study, our research group, in collaboration with teams from Israel, Spain, and Germany, discovered that microbes inhabiting freshwater lakes and oceans possess rhodopsins that bind not only retinal pigments but also xanthophyll carotenoids, such as zeaxanthin and lutein. These carotenoids function as light-harvesting antennas, transferring absorbed energy to the retinal pigment. Moreover, the study revealed that rhodopsins with these light-harvesting antennas are widely distributed among aquatic microbes.

This discovery suggests that rhodopsins in aquatic ecosystems, equipped with light-harvesting antennas, absorb significantly more solar energy than previously estimated. To understand ecosystems comprehensively, it is crucial to evaluate the light-harvesting efficiency of organisms and accurately quantify the influx of solar energy into these systems. This research is expected to advance our global understanding of aquatic ecosystems.