Murray Bayleigh, Ertekin Emine, Dailey Micah, Soulier Nathan T, Shen Gaozhong, Bryant Donald A, Perez-Fernandez Cesar, DiRuggiero Jocelyne
Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA.
Department of Biochemistry and Molecular Biology, The Pennsylvania State University, State College, PA 16802, USA.
Microorganisms. 2022 Jun 11;10(6):1198. doi: 10.3390/microorganisms10061198.
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 isolates from deserts around the world synthesize chlorophyll , an FRL-specialized chlorophyll when FRL is the sole light source. The metagenome-assembled genomes of these isolates encoded chlorophyll 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 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.
在极度干旱的沙漠中，石内微生物群落生存在岩石的孔隙和裂缝中，这种环境有助于保水并过滤紫外线辐射。岩石定殖区富含远红光（FRL）而可见光匮乏。这对作为石内群落主要生产者的蓝细菌构成了挑战。许多蓝细菌物种能够进行远红光光适应（FaRLiP），在这个过程中，远红光诱导合成特殊叶绿素并重塑光合机构，从而使其能够在远红光条件下生长。虽然在各种低光照环境的蓝细菌中都有关于远红光光适应的报道，但我们对石内蓝细菌的光适应性的了解仍然有限。在这里，我们证明，当远红光为唯一光源时，从世界各地沙漠分离得到的石内蓝细菌会合成叶绿素 ，这是一种对远红光有特异性的叶绿素。这些分离菌株的宏基因组组装基因组编码了叶绿素 合酶以及实现远红光光适应反应所需的所有基因。我们还提供了证据，证明远红光会引起一种 分离菌株的主要捕光复合体发生变化。这些发现表明，极度干旱沙漠中的石内蓝细菌利用远红光光适应来适应其岩石栖息地独特的光透射光谱。
