Virus-like particles in an apochlorotic flagellate in Hiroshima Bay, Japan

Nagasaki, Keisuke; Andô, Masashi; Imai, Ichiro; Itakura, Shigeru; Ishida, Yoshiaki

doi:10.3354/meps096307

Cited by 22 publications

(20 citation statements)

References 10 publications

(14 reference statements)

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“…Sections of similar cells in material collected from nature, but not explicitly identified, are present in publications by Sieburth et al (1988) and Nagasaki et al (1993). Vørs (1992a) extended the size range of T. subtilis to 2-66 4-14 mm, but named the pointed end of the cell 'anterior' in spite of its variable and often posterior direction during swimming (Vørs, 1992a).…”

Section: Introductionmentioning

confidence: 99%

Telonema antarcticum sp. nov., a common marine phagotrophic flagellate

Klaveness

Shalchian-Tabrizi

Thomsen

et al. 2005

International Journal of Systematic and Evolutionary Microbiology

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Telonema is a widely distributed group of phagotrophic flagellates with two known members. In this study, the structural identity and molecular phylogeny of Telonema antarcticum was investigated and a valid description is proposed. Molecular phylogeny was studied using small-subunit rRNA (SSU rRNA) gene sequences. The pear-shaped cell had two subequal flagella that emerged laterally on the truncated antapical tail. One flagellum had tripartite hairs. The cell was naked, but had subsurface vesicles containing angular paracrystalline bodies of an unknown nature. A unique complex cytoskeletal structure, the subcortical lamina, was found to be an important functional and taxonomic feature of the genus. Telonema has an antero-ventral depression where food particles are ingested and then transferred to a conspicuous anterior food vacuole. The molecular phylogeny inferred from the SSU rRNA gene sequence suggested that Telonema represents an isolated and deep branch among the tubulocristate protists.

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Section: Introductionmentioning

confidence: 99%

Telonema antarcticum sp. nov., a common marine phagotrophic flagellate

Klaveness

Shalchian-Tabrizi

Thomsen

et al. 2005

International Journal of Systematic and Evolutionary Microbiology

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“…Nagasaki et al (40,42) observed VLPs in marine apochlorotic flagellates and suggested that viral infection might be one of the factors affecting their dynamics. Garza and Suttle (15) isolated and characterized a large dsDNA virus infecting a marine heterotrophic nanoflagellate, Bodo sp., which also shared some characteristics with viruses belonging to the family Phycodnaviridae.…”

mentioning

confidence: 99%

Isolation and Characterization of a Novel Single-Stranded RNA Virus Infectious to a Marine Fungoid Protist, Schizochytrium sp. (Thraustochytriaceae, Labyrinthulea)

Takao

Nagasaki

Mise

et al. 2005

Appl Environ Microbiol

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Thraustochytrids are cosmopolitan osmoheterotrophic microorganisms that play important roles as decomposers, producers of polyunsaturated fatty acids, and pathogens of mollusks, especially in coastal ecosystems. SssRNAV, a novel single-stranded RNA (ssRNA) virus infecting the marine fungoid protist Schizochytrium sp. (Labyrinthulea, Thraustochytriaceae) was isolated from the coastal water of Kobe Harbor, Japan, in July 2000, and its basic characteristics were examined. The virus particle is icosahedral, lacks a tail, and is ca. 25 nm in diameter. SssRNAV formed crystalline arrays and random assemblies within the cytoplasm of host cells, and it was also concentrated along the intracellular membrane structures. By means of one-step growth experiments, the lytic cycle and the burst size were estimated to be <8 h and 5.8 ؋ 10 3 to 6.4 ؋ 10 4 infectious units per host cell, respectively. SssRNAV had a single molecule of ssRNA that was approximately 10.2 kb long, three major proteins (37, 34, and 32 kDa), and two minor proteins (80 and 18 kDa). Although SssRNAV was considered to have some similarities with invertebrate viruses belonging to the family Dicistroviridae based on its partial nucleotide sequence, further genomic analysis is required to determine the detailed classification and nomenclature of SssRNAV. Our results indicate that viral infection is one of the significant factors controlling the dynamics of thraustochytrids and provide new insights into understanding the ecology of these organisms.

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“…Bratbak et al (1993Bratbak et al ( , 1995 suggested, based on the results of a mesocosm study, that viral activity may prevent or terminate the development of Erniliania huxleyi blooms. Nagasaki et al (1993Nagasaki et al ( , 1994 observed the increase of virus-like particles (VLPs) in Heterosigma akashiwo cells at the final stage of a red tide caused by this alga. These results supported the significance of viral impacts on the rapid termination of phytoplankton blooms.…”

Section: Introductionmentioning

confidence: 99%

A close relationship between algicidal bacteria and termination of Heterosigma akashiwo (Raphidophyceae) blooms in Hiroshima Bay, Japan

Mc¹,

Yoshinaga²,

Imai³

et al. 1998

Mar. Ecol. Prog. Ser.

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ABSTRACT. Blooms of the noxious red tide phytoplankton Heterosigma akashiwo (Raphidophyceae) occurred in Hiroshima Bay. Japan. in 1994 and 1995. During these blooms we monitored rnicroorganisms which killed H. akashiwo by use of the microplate MPN (most probable number) method using an axenic culture of H. akashiwo as a susceptible host organism. At every sampling site abundance of algicidal microorganisms in seawater samples filtered through 0 8 pm nuclepore filters increased rapidly during the termination period of each bloom. However, the number of algicidal microorganisms In seawater samples filtered through 0 2 pm nuclepore filters was less abundant and correlated poorly with the extinction of H, akashiwo blooms. The latter samples were assumed to indicate viral activity. Thus, it is possible that H. akashiwo-killing bacteria (HAKB) played a more dominant role in the terrninatlon of the blooms in 1994 and 1995 in Hiroshima Bay than viruses. The number of algicidal bacteria targeting Chattonella antiqua (Raphidophyceae), which was not detected during the investigation period, was 1 or 2 orders of magnitude lower than that of HAKB. We isolated some HAKB strains capable of causing mortality in H. akashiwo. These results suggest that the population dynamics of algicidal bacteria has a close relationship to the blooms of the phytoplankton, and that, in marine ecosystems, algicidal bacteria targeting specific phytoplankton may be one of the agents which regulate the change of species structure of phytoplankton communities.

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Virus-like particles in an apochlorotic flagellate in Hiroshima Bay, Japan

Cited by 22 publications

References 10 publications

Telonema antarcticum sp. nov., a common marine phagotrophic flagellate

Telonema antarcticum sp. nov., a common marine phagotrophic flagellate

Isolation and Characterization of a Novel Single-Stranded RNA Virus Infectious to a Marine Fungoid Protist, Schizochytrium sp. (Thraustochytriaceae, Labyrinthulea)

A close relationship between algicidal bacteria and termination of Heterosigma akashiwo (Raphidophyceae) blooms in Hiroshima Bay, Japan

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