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Applied and Environmental Microbiology, May 2004, p. 2941-2951, Vol. 70, No. 5
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.5.2941-2951.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Viral Activity in Two Contrasting Lake Ecosystems

Yvan Bettarel,1,{dagger} Télesphore Sime-Ngando,1* Christian Amblard,1 and John Dolan2

Laboratoire de Biologie des Protistes, UMR CNRS 6023, Université Blaise Pascal (Clermont-Ferrand II), 63177 Aubière Cedex,1 Laboratoire Océanologique, UMR CNRS 7093, 6023 Villefranche-sur-Mer, France2

Received 19 November 2003/ Accepted 9 February 2004

For aquatic systems, especially freshwaters, there is little data on the long-term (i.e., >6-month period) and depth-related variability of viruses. In this study, we examined virus-induced mortality of heterotrophic bacteria over a 10-month period and throughout the water column in two lakes of the French Massif Central, the oligomesotrophic Lake Pavin and the eutrophic Lake Aydat. Concurrently, we estimated nonviral mortality through heterotrophic nanoflagellate and ciliate bacterivory. Overall, viral infection parameters were much less variable than bacterial production. We found that the frequency of visibly infected cells (FVIC), estimated using transmission electron microscopy, peaked in both lakes at the end of spring (May to June) and in early autumn (September to October). FVIC values were significantly higher in Lake Pavin (mean [M] = 1.6%) than in Lake Aydat (M = 1.1%), whereas the opposite trend was observed for burst sizes, which averaged 25.7 and 30.2 virus particles bacterium–1, respectively. We detected no significant depth-related differences in FVIC or burst size. We found that in both lakes the removal of bacterial production by flagellate grazing (MPavin = 37.7%, MAydat = 18.5%) was nearly always more than the production removed by viral lysis (MPavin = 16.2%, MAydat = 19%) or ciliate grazing (MPavin = 2.7%, MAydat = 8.8%). However, at specific times and locations, viral lysis prevailed over protistan grazing, for example, in the anoxic hypolimnion of Lake Aydat. In addition, viral mortality represented a relatively constant mortality source in a bacterial community showing large variations in growth rate and subject to large variations in loss rates from grazers. Finally, although viruses did not represent the main agent of bacterial mortality, our data seem to show that their relative importance was higher in the less productive system.

* Corresponding author. Mailing address: Laboratoire de Biologie des Protistes, UMR CNRS 6023, Université Blaise Pascal (Clermont-Ferrand II), 24 Avenue des Landais, 63177 Aubière Cedex, France. Phone: 33 4 73 40 78 36. Fax: 33 4 73 40 76 70. E-mail: Telesphore.SIME-NGANDO{at}univ-bpclermont.fr.

{dagger} Present address: Smithsonian Environmental Research Center, Edgewater, MD 21037.

Applied and Environmental Microbiology, May 2004, p. 2941-2951, Vol. 70, No. 5
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.5.2941-2951.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



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  • Colombet, J., Sime-Ngando, T., Cauchie, H. M., Fonty, G., Hoffmann, L., Demeure, G. (2006). Depth-related gradients of viral activity in lake pavin.. Appl. Environ. Microbiol. 72: 4440-4445 [Abstract] [Full Text]  


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