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Isolation and characterization of a single-stranded RNA virus infecting the bloom-forming diatom Chaetoceros socialis.

ABSTRACT: 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.

SUBMITTER: Tomaru Y

PROVIDER: S-EPMC2675228 | biostudies-literature | 2009 Apr

REPOSITORIES: biostudies-literature

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Isolation and characterization of a single-stranded RNA virus infecting the bloom-forming diatom Chaetoceros socialis.

Tomaru Yuji Y Takao Yoshitake Y Suzuki Hidekazu H Nagumo Tamotsu T Nagasaki Keizo K

Applied and environmental microbiology 20090220 8

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 w ...[more]

PMID: 19233955

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Project description:Parasitic Chytridiomycota (chytrids) are ecologically significant in various aquatic ecosystems, notably through their roles in controlling bloom-forming phytoplankton populations and in facilitating the transfer of nutrients from inedible algae to higher trophic levels. The diversity and study of these obligate parasites, while critical to understand the interactions between pathogens and their hosts in the environment, have been hindered by challenges inherent to their isolation and stable long-term maintenance under laboratory conditions. Here, we isolated an obligate chytrid parasite (CCAP 4086/1) on the freshwater bloom-forming diatom Asterionella formosa and characterized its infectious cycle under controlled conditions. Phylogenetic analyses based on 18S, 5.8S, and 28S ribosomal DNAs (rDNAs) revealed that this strain belongs to the recently described clade SW-I within the Lobulomycetales. All morphological features observed agree with the description of the known Asterionella parasite Zygorhizidium affluens Canter. We thus provide a phylogenetic placement for this chytrid and present a robust and simple assay that assesses both the infection success and the viability of the host. We also validate a cryopreservation method for stable and cost-effective long-term storage and demonstrate its recovery after thawing. All the above-mentioned tools establish a new gold standard for the isolation and long-term preservation of parasitic aquatic chytrids, thus opening new perspectives to investigate the diversity of these organisms and their physiology in a controlled laboratory environment.IMPORTANCE Despite their ecological relevance, parasitic aquatic chytrids are understudied, especially due to the challenges associated with their isolation and maintenance in culture. Here we isolated and established a culture of a chytrid parasite infecting the bloom-forming freshwater diatom Asterionella formosa The chytrid morphology suggests that it corresponds to the Asterionella parasite known as Zygorhizidium affluens The phylogenetic reconstruction in the present study supports the hypothesis that our Z. affluens isolate belongs to the order Lobulomycetales and clusters within the novel clade SW-I. We also validate a cryopreservation method for stable and cost-effective long-term storage of parasitic chytrids of phytoplankton. The establishment of a monoclonal pathosystem in culture and its successful cryopreservation opens the way to further investigate this ecologically relevant parasitic interaction.

Dataset Information

Isolation and characterization of a single-stranded RNA virus infecting the bloom-forming diatom Chaetoceros socialis.

Publications

Isolation and characterization of a single-stranded RNA virus infecting the bloom-forming diatom Chaetoceros socialis.

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