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Aquatic Microbial Ecology

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AME 14:215-222 (1998)  -  doi:10.3354/ame014215

Measurements of DNA damage and photoreactivation imply that most viruses in marine surface waters are infective

Steven W. Wilhelm1,*, Markus G. Weinbauer2, Curtis A. Suttle1,**, Ralph J. Pledger3, David L. Mitchell3

1Departments of Earth and Ocean Sciences (Oceanography), Botany and Microbiology, The University of British Columbia, 6270 University Blvd, Vancouver, British Columbia V6T 1Z4, Canada
2National Research Centre for Biotechnology, Division Microbiology, Mascheroder Weg 1, D-38124 Braunschweig, Germany
3The University of Texas M.D. Anderson Cancer Center, Department of Carcinogenesis, Park Road 1, Smithville, Texas 78957, USA
*Present address: National Water Research Institute, Aquatic Ecosystem Conservation Branch, 867 Lakeshore Road, PO Box 5050, Burlington, Ontario L7R 4A6, Canada
**Addressee for correspondence. E-mail:

The proportion of viruses in natural marine communities that are potentially infectious was inferred from the relationship between DNA damage and the loss of infectivity in marine viral isolates and measurements of the DNA damage in natural viral communities. Several viral isolates which infect marine Vibrio spp. were exposed to UV-C radiation and the concentration of cyclobutane pyrimidine dimers in the viral DNA was measured with a highly sensitive radioimmunoassay. The loss of infectivity in the UV-exposed isolates was also determined under conditions which either activated or repressed the blue light dependent photolyase enzyme in host cells in order to examine the damage-dependent response of this bacterial repair system. In addition, the accumulation of DNA photodamage during the solar day was measured in DNA isolated from natural viral communities collected along a transect in the western Gulf of Mexico. Using the correlation between DNA damage and infectivity for one of the viral isolates, we estimated the proportion of the natural viral community which was infective. The results imply that, due to light-mediated repair of damaged viral DNA by host-cell mechanisms (photoreactivation), greater than 50% of the viruses in natural communities are infective despite high rates of DNA damage. Furthermore, the accumulation of cyclobutane pyrimidine dimers was highest at the station where the surface mixed layer was shallowest, emphasizing the importance of mixing depth in relation to the accumulation of DNA damage. These experiments demonstrate that physical parameters such as mixing depth are critically interwoven with light penetration in influencing the infectivity of marine viral communities.

Marine viruses · Pyrimidine dimers · UV · Photoreactivation

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