Degree of ultraviolet radiation damage and repair capabilities are related to G+C content in marine vibriophages

A key issue in the ecology of viruses in the marine environment is the rate of viral production and decay. The ultraviolet (UV) radiation in sunlight has been found to cause loss of infectivity in marine bacteriophages at rates nearly equal to all other decay mechanisms combined. There are 2 main host-mediated mechanisms that can repair UV-damaged phage DNA: photoreactivation and excision repair. Both these mechanisms were investigated in 2 marine Vibrio parahaemolyticus hosts as they catalyzed the reactivation of 7 phages. Photoreactivation was the dominant repair mode in all but one case. A significant correlation was found between G+C content of the phage DNAs (16 to 70%) and degree of DNA damage (r = 0.955), indicating a strong relationship between the number of thymine dimer targets and the capability to photoreactivate DNA damage. Evolution of high G+C content may be a strategy for protection from UV damage in marine phages.