Isolation and Characterization of a Novel Single-Stranded RNA Virus Infecting the Bloom-Forming Diatom Rhizosolenia setigera

Abstract

A novel single-stranded RNA (ssRNA) virus specifically infecting the bloom-forming diatom Rhizosolenia setigera (R. setigera RNA virus [RsRNAV]) was isolated from Ariake Sea, Japan. Viral replication occurred within the cytoplasm, and the virus particle was icosahedral, lacked a tail, and was 32 nm in diameter on average. The major nucleic acid extracted from the RsRNAV particles was an ssRNA molecule 11.2 kb in length, although smaller RNA molecules (0.6, 1.2, and 1.5 kb) were occasionally observed. The major structural proteins of RsRNAV were 41.5, 41.0, and 29.5 kDa. Inter-and intraspecies host specificity tests revealed that RsRNAV is not only species specific but also strain specific and that its intraspecies host specificity is diverse among virus clones. The latent period of RsRNAV was 2 days, and the burst sizes were 3,100 and 1,010 viruses per host cell when viruses were inoculated into the host culture at the exponential and stationary growth phases, respectively, at 15°C under a 12-h-12-h light-dark cycle of ca. 110 mol of photons m ؊2 s ؊1 with cool white fluorescent illumination. To our knowledge, this is the first report describing the biological properties of a virus infecting a diatom. Further studies on RsRNAV will be helpful in understanding the ecological relationship between diatoms and viruses in nature.

Transformation of iodate to iodide in marine phytoplankton driven by cell senescence

“…When cells become extremely permeable under stressful conditions, such as nutrient limitation or viral infection, metabolites will be released back into the surrounding media and can react with the components of that media, including iodate. The release of cellular material can be hastened during this time by direct cell lysis mediated either by viruses (Nagasaki et al 2004, Bettarel et al 2005 or apotosis (Antunes et al 2001, Segovia et al 2003. In the present study, we cannot determine which process caused the cells to lyse, but evidence that this process was occurring can be found in the decrease in cells containing intact chloroplasts, as observed by microscopy, and the subsequent increase in bacterial numbers, presumably from the release of labile dissolved organic matter (DOM).…”

“…Cells get infected by specific viruses, which induce a loss in the viability of the algal cell and, hence, automortality (Suttle 1992, Bratbak et al 1998, Nagasaki et al 2004, Bettarel et al 2005.…”

The place of diatoms in the biofuels industry

“…Phytomyxea (plasmodiophorids) parasites have also been shown to parasitize diatoms [160]. Diatom viruses were first described in 2004 [161] and are either ssRNA or ssDNA viruses that infect the genera Rhizosolenia or Chaetoceros [162]. It is likely that the measures to deal with predation and pathogens that are being considered for other classes of algae will need to be applied to diatoms as well for biofuels production.…”

Phaeocystis and its interaction with viruses

“…Unicellular photosynthetic organisms are a major group of organisms in natural aquatic communities and viruses have been recognized as mortality agents for phytoplankton (Van Etten et al 1991;Reisser 1993;Brussaard 2004). Viruses or virus-like particles have been reported in many diVerent taxa of eukaryotic algae, including harmful algal bloom (HAB) species (see review by Brussaard 2004;Nagasaki et al 2004;Tomaru et al 2004;Baudoux and Brussaard 2005).…”