Uncovering cryptochrome/photolyase gene diversity in aquatic microbiomes exposed to diverse UV-B regimes

During evolution, microorganisms exposed to high amounts of UV-B irradiation developed fine-tuned photo-enzymes called ‘photolyases’ to cope with DNA damage caused by UV-B. These photoreceptors, belonging to the cryptochrome/photolyase family (CPF), have been well characterized at the genomic and proteomic level in bacteria isolated from a wide range of environments. In this work, we go further towards studying the abundance of CPF in aquatic microbial communities from different geographic regions across the globe. Metagenomics data combined with geo-referenced solar irradiation measurements indicated that the higher the UV-B level in the microbiome’s environment, the higher the abundance of CPF genes and lower the microbial diversity. A connection between CPF abundance and radiation intensity/photoperiod was found. Likewise, cryptochrome-like genes were found to be abundant in most exposed microbiomes, indicating a complementary role to standard photolyases. We observed that CPFs are more likely to be present in dominant taxa of the highly irradiated microbiomes, suggesting an evolutionary force for survival and dominance under extreme solar exposure. This work reports 3 novel CPF clades, proving the potential of global metagenomic analyses in detecting novel proteins.