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  • 1
    In: Environmental Microbiology, Wiley, Vol. 9, No. 6 ( 2007-06), p. 1376-1383
    Abstract: We studied the ecological relationships between the bloom‐forming dinoflagellate Heterocapsa circularisquama and its infectious viruses in field surveys conducted in western Japan. The occurrence of H. circularisquama blooms in Imari Bay during 2002 and in Ago Bay during 2002 and 2004 was accompanied by specific increase in abundance of viruses lytic to H. circularisquama . Using northern dot‐blot analysis, ∼96% of the clonal virus isolates collected in the field surveys positively reacted with a molecular probe specific for HcRNAV ( H. circularisquama RNA virus); hence, viral impacts on H. circularisquama population observed in these field surveys are considered largely due to HcRNAV and/or its closely related viruses. The dynamics of type UA viruses and type CY viruses having complementary host ranges to H. circularisquama clones were different in each survey and considered to reflect fluctuations in abundance of their suitable host cells in situ . The dynamics of H. circularisquama and its viruses in Ago Bay from 2002 to 2004 suggests the concentration of HcRNAV in the sediment prior to the host's blooming season is a significant factor in determining the size and length of the H. circularisquama blooms. These results support the hypothesis that HcRNAV infection is one of the significant factors affecting the population dynamics of H. circularisquama in both quantity (biomass) and quality (clonal composition).
    Type of Medium: Online Resource
    ISSN: 1462-2912 , 1462-2920
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2007
    detail.hit.zdb_id: 2020213-1
    SSG: 12
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  • 2
    In: Journal of General Virology, Microbiology Society, Vol. 92, No. 8 ( 2011-08-01), p. 1960-1970
    Abstract: Heterocapsa circularisquama RNA virus is a non-enveloped icosahedral ssRNA virus infectious to the harmful bloom-forming dinoflagellate, H. circularisquama , and which is assumed to be the major natural agent controlling the host population. The viral capsid is constructed from a single gene product. Electron cryo-microscopy revealed that the virus has a diameter of 34 nm and T  = 3 symmetry. The 180 quasi-equivalent monomers have an unusual arrangement in that each monomer contributes to a ‘bump’ on the surface of the protein. Though the capsid protein probably has the classic ‘jelly roll’ β-sandwich fold, this is a new packing arrangement and is distantly related to the other positive-sense ssRNA virus capsid proteins. The handedness of the structure has been determined by a novel method involving high resolution scanning electron microscopy of the negatively stained viruses and secondary electron detection.
    Type of Medium: Online Resource
    ISSN: 0022-1317 , 1465-2099
    RVK:
    RVK:
    Language: English
    Publisher: Microbiology Society
    Publication Date: 2011
    detail.hit.zdb_id: 2007065-2
    SSG: 12
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  • 3
    In: Microbes and Environments, Japanese Society of Microbial Ecology, Vol. 22, No. 3 ( 2007), p. 207-213
    Type of Medium: Online Resource
    ISSN: 1342-6311 , 1347-4405
    Language: English
    Publisher: Japanese Society of Microbial Ecology
    Publication Date: 2007
    detail.hit.zdb_id: 2039087-7
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    American Society for Microbiology ; 2004
    In:  Applied and Environmental Microbiology Vol. 70, No. 2 ( 2004-02), p. 704-711
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 70, No. 2 ( 2004-02), p. 704-711
    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 μmol 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.
    Type of Medium: Online Resource
    ISSN: 0099-2240 , 1098-5336
    RVK:
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2004
    detail.hit.zdb_id: 223011-2
    detail.hit.zdb_id: 1478346-0
    SSG: 12
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  • 5
    Online Resource
    Online Resource
    American Society for Microbiology ; 2005
    In:  Applied and Environmental Microbiology Vol. 71, No. 7 ( 2005-07), p. 3599-3607
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 71, No. 7 ( 2005-07), p. 3599-3607
    Abstract: Heterosigma akashiwo virus (HaV) is a large double-stranded DNA virus infecting the single-cell bloom-forming raphidophyte (golden brown alga) H. akashiwo . A molecular phylogenetic sequence analysis of HaV DNA polymerase showed that it forms a sister group with Phycodnaviridae algal viruses. All 10 examined HaV strains, which had distinct intraspecies host specificities, included an intein (protein intron) in their DNA polymerase genes. The 232-amino-acid inteins differed from each other by no more than a single nucleotide change. All inteins were present at the same conserved position, coding for an active-site motif, which also includes inteins in mimivirus (a very large double-stranded DNA virus of amoebae) and in several archaeal DNA polymerase genes. The HaV intein is closely related to the mimivirus intein, and both are apparently monophyletic to the archaeal inteins. These observations suggest the occurrence of horizontal transfers of inteins between viruses of different families and between archaea and viruses and reveal that viruses might be reservoirs and intermediates in horizontal transmissions of inteins. The homing endonuclease domain of the HaV intein alleles is mostly deleted. The mechanism keeping their sequences basically identical in HaV strains specific for different hosts is yet unknown. One possibility is that rapid and local changes in the HaV genome change its host specificity. This is the first report of inteins found in viruses infecting eukaryotic algae.
    Type of Medium: Online Resource
    ISSN: 0099-2240 , 1098-5336
    RVK:
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2005
    detail.hit.zdb_id: 223011-2
    detail.hit.zdb_id: 1478346-0
    SSG: 12
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  • 6
    Online Resource
    Online Resource
    American Society for Microbiology ; 2005
    In:  Applied and Environmental Microbiology Vol. 71, No. 7 ( 2005-07), p. 3528-3535
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 71, No. 7 ( 2005-07), p. 3528-3535
    Abstract: Diatoms are a major phytoplankton group that play important roles in maintaining oxygen levels in the atmosphere and sustaining the primary nutritional production of the aquatic environment. Among diatoms, the genus Chaetoceros is one of the most abundant and widespread. Temperature, climate, salinity, nutrients, and predators were regarded as important factors controlling the abundance and population dynamics of diatoms. Here we show that a viral infection can occur in the genus Chaetoceros and should therefore be considered as a potential mortality source. Chaetoceros salsugineum nuclear inclusion virus (CsNIV) is a 38-nm icosahedral virus that replicates within the nucleus of C. salsugineum. The latent period was estimated to be between 12 and 24 h, with a burst size of 325 infectious units per host cell. CsNIV has a genome structure unlike that of other viruses that have been described. It consists of a single molecule of covalently closed circular single-stranded DNA (ssDNA; 6,005 nucleotides), as well as a segment of linear ssDNA (997 nucleotides). The linear segment is complementary to a portion of the closed circle creating a partially double-stranded genome. Sequence analysis reveals a low but significant similarity to the replicase of circoviruses that have a covalently closed circular ssDNA genome. This new host-virus system will be useful for investigating the ecological relationships between bloom-forming diatoms and other viruses in the marine system. Our study supports the view that, given the diversity and abundance of plankton, the ocean is a treasury of undiscovered viruses.
    Type of Medium: Online Resource
    ISSN: 0099-2240 , 1098-5336
    RVK:
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2005
    detail.hit.zdb_id: 223011-2
    detail.hit.zdb_id: 1478346-0
    SSG: 12
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  • 7
    In: Journal of Virology, American Society for Microbiology, Vol. 81, No. 3 ( 2007-02), p. 1372-1378
    Abstract: Viruses are extremely abundant in seawater and are believed to be significant pathogens to photosynthetic protists (microalgae). Recently, several novel RNA viruses were found to infect marine photosynthetic protists; one of them is HcRNAV, which infects Heterocapsa circularisquama ( Dinophyceae ). There are two distinct ecotypes of HcRNAV with complementary intraspecies host ranges. Nucleotide sequence comparison between them revealed remarkable differences in the coat protein coding gene resulting in a high frequency of amino acid substitutions. However, the detailed mechanism supporting this intraspecies host specificity is still unknown. In this study, virus inoculation experiments were conducted with compatible and incompatible host-virus combinations to investigate the mechanism determining intraspecies host specificity. Cells were infected by adding a virus suspension directly to a host culture or by transfecting viral RNA into host cells by particle bombardment. Virus propagation was monitored by Northern blot analysis with a negative-strand-specific RNA probe, transmission electron microscopy, and a cell lysis assay. With compatible host-virus combinations, propagation of infectious progeny occurred regardless of the inoculation method used. When incompatible combinations were used, direct addition of a virus suspension did not even result in viral RNA replication, while in host cells transfected with viral RNA, infective progeny virus particles with a host range encoded by the imported viral RNA were propagated. This indicates that the intraspecies host specificity of HcRNAV is determined by the upstream events of virus infection. This is the first report describing the reproductive steps of an RNA virus infecting a photosynthetic protist at the molecular level.
    Type of Medium: Online Resource
    ISSN: 0022-538X , 1098-5514
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2007
    detail.hit.zdb_id: 1495529-5
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  • 8
    In: Science of The Total Environment, Elsevier BV, Vol. 770 ( 2021-05), p. 145220-
    Type of Medium: Online Resource
    ISSN: 0048-9697
    RVK:
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2021
    detail.hit.zdb_id: 1498726-0
    detail.hit.zdb_id: 121506-1
    SSG: 12
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  • 9
    In: Scientific Reports, Springer Science and Business Media LLC, Vol. 11, No. 1 ( 2021-11-24)
    Abstract: Diatoms are one of the most prominent oceanic primary producers and are now recognized to be distributed throughout the world. They maintain their population despite predators, infections, and unfavourable environmental conditions. One of the smallest diatoms, Chaetoceros tenuissimus , can coexist with infectious viruses during blooms. To further understand this relationship, we sequenced the C. tenuissimus strain NIES-3715 genome. A gene fragment of a replication-associated gene from the infectious ssDNA virus (designated endogenous virus-like fragment, EVLF) was found to be integrated into each 41 Mb of haploid assembly. In addition, the EVLF was transcriptionally active and conserved in nine other C. tenuissimus strains from different geographical areas, although the primary structures of their proteins varied. The phylogenetic tree further suggested that the EVLF was acquired by the ancestor of C. tenuissimus . Additionally, retrotransposon genes possessing a reverse transcriptase function were more abundant in C. tenuissimus than in Thalassiosira pseudonana and Phaeodactylum tricornutum . Moreover, a target site duplication, a hallmark for long interspersed nuclear element retrotransposons, flanked the EVLF. Therefore, the EVLF was likely integrated by a retrotransposon during viral infection. The present study provides further insights into the diatom-virus evolutionary relationship.
    Type of Medium: Online Resource
    ISSN: 2045-2322
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 2615211-3
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  • 10
    Online Resource
    Online Resource
    The Plankton Society of Japan/The Japanese Association of Benthology ; 2009
    In:  Plankton and Benthos Research Vol. 4, No. 4 ( 2009), p. 129-134
    In: Plankton and Benthos Research, The Plankton Society of Japan/The Japanese Association of Benthology, Vol. 4, No. 4 ( 2009), p. 129-134
    Type of Medium: Online Resource
    ISSN: 1880-8247 , 1882-627X
    Language: English
    Publisher: The Plankton Society of Japan/The Japanese Association of Benthology
    Publication Date: 2009
    detail.hit.zdb_id: 2657634-X
    SSG: 12
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