This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Pinheiro, M. D. O.
Right arrow Articles by Bols, N. C.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Pinheiro, M. D. O.
Right arrow Articles by Bols, N. C.
Agricola
Right arrow Articles by Pinheiro, M. D. O.
Right arrow Articles by Bols, N. C.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, January 2007, p. 643-649, Vol. 73, No. 2
0099-2240/07/$08.00+0     doi:10.1128/AEM.02363-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Use of Tetrahymena thermophila To Study the Role of Protozoa in Inactivation of Viruses in Water{triangledown}

Marcel D. O. Pinheiro,1 Mary E. Power,1 Barbara J. Butler,1 Vivian R. Dayeh,1 Robin Slawson,2 Lucy E. J. Lee,2 Denis H. Lynn,3 and Niels C. Bols1*

Department of Biology, University of Waterloo, Waterloo, Ontario, Canada,1 Department of Biology, Wilfrid Laurier University, Waterloo, Ontario, Canada,2 Department of Zoology, University of Guelph, Guelph, Ontario, Canada3

Received 5 October 2006/ Accepted 8 November 2006

The ability of a ciliate to inactivate bacteriophage was studied because these viruses are known to influence the size and diversity of bacterial populations, which affect nutrient cycling in natural waters and effluent quality in sewage treatment, and because ciliates are ubiquitous in aquatic environments, including sewage treatment plants. Tetrahymena thermophila was used as a representative ciliate; T4 was used as a model bacteriophage. The T4 titer was monitored on Escherichia coli B in a double-agar overlay assay. T4 and the ciliate were incubated together under different conditions and for various times, after which the mixture was centrifuged through a step gradient, producing a top layer free of ciliates. The T4 titer in this layer decreased as coincubation time increased, but no decrease was seen if phage were incubated with formalin-fixed Tetrahymena. The T4 titer associated with the pellet of living ciliates was very low, suggesting that removal of the phage by Tetrahymena inactivated T4. When Tetrahymena cells were incubated with SYBR gold-labeled phage, fluorescence was localized in structures that had the shape and position of food vacuoles. Incubation of the phage and ciliate with cytochalasin B or at 4°C impaired T4 inactivation. These results suggest the active removal of T4 bacteriophage from fluid by macropinocytosis, followed by digestion in food vacuoles. Such ciliate virophagy may be a mechanism occurring in natural waters and sewage treatment, and the methods described here could be used to study the factors influencing inactivation and possibly water quality.

* Corresponding author. Mailing address: Department of Biology, University of Waterloo, 200 University Ave. W, Waterloo, Ontario N2L 3G1, Canada. Phone: (519) 888-4567, ext. 33993. Fax: (519) 746-0614. E-mail: ncbols{at}uwaterloo.ca.

{triangledown} Published ahead of print on 17 November 2006.

Applied and Environmental Microbiology, January 2007, p. 643-649, Vol. 73, No. 2
0099-2240/07/$08.00+0     doi:10.1128/AEM.02363-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»