Weinbauer, M.G., S.W. Wilhelm and C.A. Suttle. 1996. Significance of photoreactivation for maintaining high concentrations of infectious viruses in the sea. Abstracts American Society Microbiology, New Orleans, LA, May 1996.

The occurrence of high concentrations of infectious viruses in surface waters has been enigmatic, since the infectivity of viruses is extremely sensitive to solar radiation. One explanation of this paradox is that damage to viral DNA by solar radiation is repaired in host cells subsequent to infection, e.g. by the light activated enzyme, photolyase. The natural viral community in samples collected from the Gulf of Mexico was damaged by solar radiation and subsequently repaired by either the natural bacterial community or the marine bacterium Vibrio natriegens kept under photoreactivating light. Photoreactivation could repair the infectivity of up to 53% of the natural virus community, and in two thirds of the samples the photoreactivation system of V. natriegens restored the infectivity of viruses which could not be repaired by light-independent mechanisms. Solar radiation induced decay rates of infectivity ranged between 0.14 to 0.16 h^-1 when integrated over the surface mixed layer in oceanic waters, indicating that the infectivity of the entire viral community is destroyed on a daily basis. However, destruction rates of virus particles integrated over the same depth ranged between 0.04 to 0.08 h^-1. Calculations using these results imply that host-mediated light-dependent repair mechanisms must have restored infectivity in 45 to 76% of the damaged viral particles. These results indicate that photoreactivation can compensate for a large fraction of UV-induced DNA damage in natural virus communities, and is essential for the survival of viruses in oceanic waters.