Searching for novel photolyases in UVC-resistant Antarctic bacteria

Ultraviolet (UV) light irradiation has serious consequences for cell survival, including DNA damage by formation of cyclobutane pyrimidine dimers (CPD) and pyrimidine (6,4) pyrimidone photoproducts. In general, the Nucleotide Excision Repair pathway repairs these lesions; however, all living forms, except placental mammals and some marsupials, produce a flavoprotein known as photolyase that directly reverses these lesions. The aim of this work was the isolation and identification of Antarctic UVC-resistant bacteria, and the search for novel photolyases. Two Antarctic water samples were UVC-irradiated (254 nm; 50-200 J m(-2)) and 12 UVC-resistant bacteria were isolated and identified by 16S rDNA amplification/analysis as members of the genera Pseudomonas, Janthinobacterium, Flavobacterium, Hymenobacter and Sphingomonas. The UVC 50% lethal dose and the photorepair ability of isolates were analyzed. The occurrence of photolyase coding sequences in Pseudomonas, Hymenobacter and Sphingomonas isolates were searched by PCR or by searching in the draft DNA genome. Results suggest that Pseudomonas and Hymenobacter isolates produce CDP-photolyases, and Sphingomonas produces two CPD-photolyases and a 6,4-photolyase. Results suggest that the Antarctic environment is an important source of genetic material for the identification of novel photolyase genes with potential biotechnological applications.