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Applied and Environmental Microbiology, November 2004, p. 6706-6713, Vol. 70, No. 11
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.11.6706-6713.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Benthic and Pelagic Viral Decay Experiments: a Model-Based Analysis and Its Applicability

Ulrike R. Fischer,1 Willy Weisz,2 Claudia Wieltschnig,1 Alexander K. T. Kirschner,1 and Branko Velimirov1*

Center for Anatomy and Cell Biology, Research Group General Microbiology, Medical University of Vienna,1 VCPC, Institute for Software Science, University of Vienna, Vienna, Austria2

Received 23 March 2004/ Accepted 8 July 2004

The viral decay in sediments, that is, the decrease in benthic viral concentration over time, was recorded after inhibiting the production of new viruses. Assuming that the viral abundance in an aquatic system remains constant and that viruses from lysed bacterial cells replace viruses lost by decay, the decay of viral particles can be used as a measure of viral production. Decay experiments showed that this approach is a useful tool to assess benthic viral production. However, the time course pattern of the decay experiments makes their interpretation difficult, regardless of whether viral decay is determined in the water column or in sediments. Different curve-fitting approaches (logarithmic function, power function, and linear regression) to describe the time course of decay experiments found in the literature are used in the present study and compared to a proposed "exponential decay" model based on the assumption that at any moment the decay is proportional to the amount of viruses present. Thus, an equation of the form dVA/dt = –k x VA leading to the time-integrated form VAt = VA0 x e–k x t was used, where k represents the viral decay rate (h–1), VAt is the viral abundance (viral particles ml–1) at time t (h), and VA0 is the initial viral abundance (viral particles ml–1). This approach represents the best solution for an accurate curve fitting based on a mathematical model for a realistic description of viral decay occurring in aquatic systems. Decay rates ranged from 0.0282 to 0.0696 h–1 (mean, 0.0464 h–1). Additionally, a mathematical model is presented that enables the quantification of the viral control of bacterial production. The viral impact on bacteria based on decay rates calculated from the different mathematical approaches varied widely within one and the same decay experiment. A comparison of the viral control of bacterial production in different aquatic environments is, therefore, improper when different mathematical formulas are used to interpret viral decay experiments.

* Corresponding author. Mailing address: Center for Anatomy and Cell Biology, Research Group General Microbiology, Medical University of Vienna, Waehringer Strasse 10, 1090 Vienna, Austria. Phone: 43 1 4277 60630. Fax: 43 1 4277 9606. E-mail: branko.velimirov{at}univie.ac.at.

Applied and Environmental Microbiology, November 2004, p. 6706-6713, Vol. 70, No. 11
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.11.6706-6713.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



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  • Bongiorni, L., Magagnini, M., Armeni, M., Noble, R., Danovaro, R. (2005). Viral Production, Decay Rates, and Life Strategies along a Trophic Gradient in the North Adriatic Sea. Appl. Environ. Microbiol. 71: 6644-6650 [Abstract] [Full Text]  


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