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Applied and Environmental Microbiology, April 2009, p. 2375-2381, Vol. 75, No. 8
0099-2240/09/$08.00+0 doi:10.1128/AEM.02580-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Isolation and Characterization of a Single-Stranded RNA Virus Infecting the Bloom-Forming Diatom Chaetoceros socialis
Yuji Tomaru,1*
Yoshitake Takao,2
Hidekazu Suzuki,3
Tamotsu Nagumo,4 and
Keizo Nagasaki1
National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research Agency, 2-17-5 Maruishi, Hatsukaichi, Hiroshima 739-0452, Japan,1 Department of Marine Bioscience, Fukui Prefectural University, 1-1 Gakuen-cho, Obama, Fukui 917-0003, Japan,2 Department of Ocean Sciences, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan,3 Department of Biology, Nippon Dental University, 1-9-20 Fujimi, Chiyoda-ku, Tokyo 102-9159, Japan4
Received 12 November 2008/ Accepted 9 February 2009
Diatoms are very significant primary producers in the world's oceans. Various environmental factors affect the depletion of diatom populations. The importance of viruses as a potential mortality source has recently been recognized. We isolated and characterized a new diatom virus (Chaetoceros socialis f. radians RNA virus [CsfrRNAV]) causing the lysis of the bloom-forming species Chaetoceros socialis Lauder f. radians (Schütt) Proschkina-Lavrenko. The virus infectious to C. socialis f. radians was isolated from water samples collected in Hiroshima Bay. Here we show the physiology, morphology, and genome characteristics of the virus clone. Virions were 22 nm in diameter and accumulated in the cytoplasm of the host cells. The latent period and the burst size were estimated to be <48 h and 66 infectious units per host cell, respectively. CsfrRNAV harbors a single-stranded RNA (ssRNA) genome and encodes at least three polypeptides of 32.0, 28.5, and 25.0 kDa. Sequencing analysis shows the length of the genome is 9,467 bases, excluding a poly(A) tail. The monophyly of CsfrRNAV and other diatom-infecting RNA viruses, Rhizosolenia setigera RNA virus and Chaetoceros tenuissimus RNA virus, was strongly supported by phylogenetic analysis based on the amino acid sequence of the RNA-dependent RNA polymerase domains. This suggested a new ssRNA virus family, Bacillariornaviridae. This discovery of CsfrRNAV may aid in further understanding the ecological dynamics of the C. socialis f. radians population in nature and the relationships between ssRNA diatom viruses and their hosts.
* Corresponding author. Mailing address: National Research Institute of Fisheries and Environment of Inland Sea, 2-17-5 Maruishi, Hatsukaichi, Hiroshima 739-0452, Japan. Phone: 81-829-55-3529. Fax: 81-829-54-1216. E-mail: tomaruy{at}affrc.go.jp
Published ahead of print on 20 February 2009.
Applied and Environmental Microbiology, April 2009, p. 2375-2381, Vol. 75, No. 8
0099-2240/09/$08.00+0 doi:10.1128/AEM.02580-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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