Substantial near-infrared radiation-driven photosynthesis of chlorophyll f-containing cyanobacteria in a natural habitat

Abstract

Far-red absorbing chlorophylls are constitutively present as chlorophyll (Chl) <i>d</i> in the cyanobacterium <i>Acaryochloris marina</i>, or dynamically expressed by synthesis of Chl <i>f</i>, red-shifted phycobiliproteins and minor amounts of Chl <i>d</i> via far-red light photoacclimation in a range of cyanobacteria, which enables them to use near-infrared-radiation (NIR) for oxygenic photosynthesis. While the biochemistry and molecular physiology of Chl <i>f</i>-containing cyanobacteria has been unraveled in culture studies, their ecological significance remains unexplored and no data on their in situ activity exist. With a novel combination of hyperspectral imaging, confocal laser scanning microscopy, and nanoparticle-based O₂ imaging, we demonstrate substantial NIR-driven oxygenic photosynthesis by endolithic, Chl <i>f</i>-containing cyanobacteria within natural beachrock biofilms that are widespread on (sub)tropical coastlines. This indicates an important role of NIR-driven oxygenic photosynthesis in primary production of endolithic and other shaded habitats.