Cyanobacteria are essential to microbial communities inhabiting translucent rocks in hyper-arid deserts. Metagenomic studies revealed unique adaptations of these cyanobacteria, but validation of the corresponding metabolic pathways remained challenging without access to isolates. Here, we present high-quality metagenome-assembled genomes for cyanobacteria, and their heterotrophic companions, isolated from endolithic substrates.

In hyper-arid deserts, endolithic microbial communities survive in the pore spaces and cracks of rocks, an environment that enhances water retention and filters UV radiation. The rock colonization zone is enriched in far-red light (FRL) and depleted in visible light. This poses a challenge to cyanobacteria, which are the primary producers of endolithic communities. Many species of cyanobacteria are capable of Far-Red-Light Photoacclimation (FaRLiP), a process in which FRL induces the synthesis of specialized chlorophylls and remodeling of the photosynthetic apparatus, providing the ability to grow in FRL. While FaRLiP has been reported in cyanobacteria from various low-light environments, our understanding of light adaptations for endolithic cyanobacteria remains limited. Here, we demonstrated that endolithic Chroococcidiopsis isolates from deserts around the world synthesize chlorophyll f, an FRL-specialized chlorophyll when FRL is the sole light source. The metagenome-assembled genomes of these isolates encoded chlorophyll f synthase and all the genes required to implement the FaRLiP response. We also present evidence of FRL-induced changes to the major light-harvesting complexes of a Chroococcidiopsis isolate. These findings indicate that endolithic cyanobacteria from hyper-arid deserts use FRL photoacclimation as an adaptation to the unique light transmission spectrum of their rocky habitat.

Cyanobacteria are essential to microbial communities inhabiting translucent rocks in hyper-arid deserts. Metagenomic studies revealed unique adaptations of these cyanobacteria but validation of the corresponding metabolic pathways remained challenging without access to isolates. Here we present high-quality metagenome assembled genomes for cyanobacteria, and their heterotrophic companions, isolated from endolithic substrates.

In hyper-arid deserts, endolithic microbial communities survive in the pore spaces and cracks of rocks, an environment that enhances water retention and filters UV radiation. The rock coloniza-tion zone is enriched in far-red light (FRL) and depleted in visible light. This poses a challenge to cyanobacteria, which are the primary producers of endolithic communities. Many species of cya-nobacteria are capable of Far-Red Light Photoacclimation (FaRLiP), a process in which FRL in-duces the synthesis of specialized chlorophylls and remodeling of the photosynthetic apparatus, providing the ability to grow in FRL. While FaRLiP has been reported in cyanobacteria from various low-light environments, our understanding of light adaptations for endolithic cyanobac-teria remains limited. Here, we demonstrated that endolithic Chroococidiopsis isolates from de-serts around the world synthesize chlorophyll f, an FRL-specialized chlorophyll when FRL is the sole light source. The metagenome-assembled genomes of these isolates encoded chlorophyll f synthase and all the genes required to implement the FaRLiP response. We also present evidence of FRL-induced changes to the major light-harvesting complexes of a Chroococidiopsis isolate. These findings indicate that endolithic cyanobacteria from hyper-arid deserts use FRL pho-to-acclimation as an adaptation to the unique light transmission spectrum of their rocky habitat.