PHOTOREACTIVATION COMPENSATES FOR UV DAMAGE AND RESTORES INFECTIVITY TO NATURAL MARINE VIRUS COMMUNITIES

We investigated the potential for photoreactivation to restore infecti vity to sunlight-damaged natural viral communities in offshore (chloro phyll a, <0.1 mu g liter(-1)), coastal (chlorophyll a, ca. 0.2 mu g li ter(-1)), and estuarine (chlorophyll a, ca. 1 to 5 pg liter(-1)) water s of the Gulf of Mexico. In 67% of samples, the light-dependent repair mechanisms of the bacterium Vibrio natriegens restored infectivity to natural viral communities which could not be repaired by light-indepe ndent mechanisms. Similarly, exposure of sunlight-damaged natural vira l communities to >312-nm-wavelength sunlight in the presence of the na tural bacterial communities restored infectivity to 21 to 26% of sunli ght-damaged viruses in oceanic waters and 41 to 52% of the damaged vir uses in coastal and estuarine waters. Wavelengths between 370 and 550 nm were responsible for restoring infectivity to the damaged viruses. These results indicate that light-dependent repair, probably photoreac tivation, compensated for a large fraction of sunlight-induced DNA dam age in natural viral communities and is potentially essential for the maintenance of high concentrations of viruses in surface waters.