Microbial rhodopsins are major contributors to the solar energy captured in the sea

• Published in: Science advances 2019-08, Vol.5 (8), p.eaaw8855
• Main Authors: Gómez-Consarnau, Laura, Raven, John A, Levine, Naomi M, Cutter, Lynda S, Wang, Deli, Seegers, Brian, Arístegui, Javier, Fuhrman, Jed A, Gasol, Josep M, Sañudo-Wilhelmy, Sergio A
• Format: Article
• Language: English
• Subjects: Ecology; Oceanography; SciAdv r-articles
• ISSN: 2375-2548; 2375-2548
• DOI: 10.1126/sciadv.aaw8855

All known phototrophic metabolisms on Earth rely on one of three categories of energy-converting pigments: chlorophyll- (rarely - ), bacteriochlorophyll- (rarely - ), and retinal, which is the chromophore in rhodopsins. While the significance of chlorophylls in solar energy capture has been studied for decades, the contribution of retinal-based phototrophy to this process remains largely unexplored. We report the first vertical distributions of the three energy-converting pigments measured along a contrasting nutrient gradient through the Mediterranean Sea and the Atlantic Ocean. The highest rhodopsin concentrations were observed above the deep chlorophyll- maxima, and their geographical distribution tended to be inversely related to that of chlorophyll- . We further show that proton-pumping proteorhodopsins potentially absorb as much light energy as chlorophyll- -based phototrophy and that this energy is sufficient to sustain bacterial basal metabolism. This suggests that proteorhodopsins are a major energy-transducing mechanism to harvest solar energy in the surface ocean.