Photoreactivation compensates for UV damage and restores infectivity to natural marine virus communities

We investigated the potential for photoreactivation to restore infectivity to sunlight-damaged natural viral communities in offshore (chlorophyll a, < 0.1 microgram liter-1), coastal (chlorophyll a, ca. 0.2 microgram liter-1), and estuarine (chlorophyll a, ca. 1 to 5 micrograms liter-1) waters 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-independent mechanisms. Similarly, exposure of sunlight-damaged natural viral communities to > 312-nm-wavelength sunlight in the presence of the natural bacterial communities restored infectivity to 21 to 26% of sunlight-damaged viruses in oceanic waters and 41 to 52% of the damaged viruses 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 photoreactivation, compensated for a large fraction of sunlight-induced DNA damage in natural viral communities and is potentially essential for the maintenance of high concentrations of viruses in surface waters.