Isolation of viruses infecting photosynthetic and nonphotosynthetic protists

Keizo Nagasaki and Gunnar Bratbak

Full Citation: Nagasaki, K., and G. Bratbak. 2010. Isolation of viruses infecting photosynthetic and nonphotosynthetic protists, p. 92-101. In S. W. Wilhelm, M. G. Weinbauer, and C. A. Suttle [eds.], Manual of Aquatic Viral Ecology. ASLO. [DOI 10.4319/mave.2010.978-0-9845591-0-7.92]

ABSTRACT: Viruses are the most abundant biological entities in aquatic environments and our understanding of their ecological significance has increased tremendously since the first discovery of their high abundance in natural waters. About 40 viruses infecting eukaryotic algae and 4 viruses infecting nonphotosynthetic protists have so far been isolated and characterized to different extents. The isolated viruses infecting phytoplankton (Chlorophyceae, Prasinophyceae, Haptophyceae, Dinophyceae, Pelagophyceae, Raphidophyceae, and Bacillariophyceae) and heterotrophic protists (Bicosoecophyceae, Acanthamoebidae, and Thraustochytriaceae) are all lytic. Some of the brown algal phaeoviruses, which infect host spores or gametes, have also been found in a latent form (lysogeny) in vegetative cells. Viruses infecting eukaryotic photosynthetic and nonphotosynthetic protists are highly diverse both in size (ca. 20-220 nm in diameter), genome type (double-strand deoxyribonucleic acid [dsDNA], single-strand [ss]DNA, ds-ribonucleic acid [dsRNA], ssRNA), and genome size [4.4-560 kb]). Availability of host-virus laboratory cultures is a necessary prerequisite for characterization of the viruses and for investigation of host-virus interactions. In this report we summarize and comment on the techniques used for preparation of host cultures and for screening, cloning, culturing, and maintaining viruses in the laboratory.