JPR Advance Access originally published online on February 1, 2006
Journal of Plankton Research 2006 28(4):407-412; doi:10.1093/plankt/fbi128
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Diversity of virus-like agents killing Microcystis aeruginosa in a hyper-eutrophic pond
1 Center for Ecological Research, Kyoto University, 509-3, 2CHOME, Hirano, Otsu 520-2113, Japan, 2 Laboratory of Environmental Biotechnology, Faculty of Engineering, Tohoku Gakuin University, 1-13-1 Chuo, Tagajo, Miyagi 985-8537, Japan, 3 Department of Biological Sciences and the Wrigley Institute for Environmental Studies, University of Southern California, Los Angeles, CA 90089-0371, USA and 4 Research Institute for Humanity and Nature (RIHN), 457-5 Motoyama Kamigamo, Kita-Ku, Kyoto 603-8047, Japan
* Corresponding Author: zen{at}chikyu.ac.jp
Received November 13, 2005; accepted in principle December 14, 2005; accepted for publication January 30, 2006; published online February 1, 2006
Communicating editor: P.J. Harrison
We demonstrated the existence of the diversity of virus-like agents killing Microcystis aeruginosa in a shallow hyper-eutrophic pond in Japan, but without specific virus isolation, once in October and twice in December 2001. The pond water was treated by chloroform, filtered throughout GF-75 filter (0.3 µm) and then incubated with axenic M. aeruginosa for 7 days. The cell density of M. aeruginosa decreased 10-fold in the course of the incubation. Results suggested that the active agent for cell death was virus-like, based upon its size fraction (from 30 kDa to 0.3 µm), sensitivity on heat-treatment, and evidence of protein protection of DNA during our extraction procedure. From our results of pulsed field gel electrophoresis (PFGE) analysis, two or four different-sized DNA bands appeared from the culture lysate in each experiment. In total, 10 different-sized bands (1090 kb) were observed from the three sample dates, suggesting that multiple virus-like agents killing M. aeruginosa existed in this pond. To our knowledge, this is the first report of the existence of virus-like agents with different genomic size that kill M. aeruginosa.