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Ichiro Imai - One of the best experts on this subject based on the ideXlab platform.
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algicidal bacteria in particle associated form and in free living form during a diatom bloom in the seto inland sea japan
Aquatic Microbial Ecology, 2010Co-Authors: Junghwan Park, Ikuo Yoshinaga, Tetsuya Nishikawa, Ichiro ImaiAbstract:To analyze the interrelated dynamics of microalgae and algicidal bacteria (i.e. bacteria that kill and utilize microalgal cells) in a seawater environment, we investigated particle-associated and free-living algicidal bacteria during a diatom bloom in the Seto Inland Sea (Japan) in the sum- mer of 2005. A conventional most probable number (MPN) protocol revealed that bacteria that are algicidal against the harmful microalga Chattonella antiqua (Raphidophyceae) increased in number towards the end of the diatom bloom, during which only a few cells of Chattonella species were observed. Relatively abundant heterotrophic bacteria were present during the bloom period, indicat- ing that the bloom promoted the growth and activity of the ambient bacterial population, including algicidal bacteria. The algicidal abilities of 487 strains isolated from the particle-associated bacteria (PAB) fraction and 249 strains isolated from the free-living bacteria (FLB) fraction were tested against axenic cultures of 3 dinoflagellates and 3 raphidophycean flagellates. About half of the PAB isolates (231/487 strains) showed algicidal activity against 1 or more tested microalgae, while only 22% of the FLB isolates (55/249 strains) were algicidal. Eighty percent of algicidal bacteria from the PAB fraction could kill multiple species of tested microalgae, whereas most of the algicidal bacteria from the FLB fraction killed only a single species. These observations suggest that diatom blooms provide a habi- tat for algicidal bacteria with a wide prey range that potentially limit harmful algal blooms caused by dinoflagellates and raphidophycean flagellates.
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Occurrence of the polyamines caldopentamine and homocaldopentamine in axenic cultures of the red tide flagellates Chattonella antiqua and Heterosigma akashiwo (Raphidophyceae).
FEMS microbiology letters, 2009Co-Authors: Naoyoshi Nishibori, Masaru Niitsu, Shinsuke Fujihara, Takefumi Sagara, Sachio Nishio, Ichiro ImaiAbstract:The polyamines caldopentamine and homocaldopentamine were detected in axenic strains of Chattonella antiqua and Heterosigma akashiwo (Raphidophyceae), respectively, as well as spermidine, the most abundant polyamine in both phytoplankton species. Trace amounts of putrescine, diaminopropane and norspermine were also detected in both species. Spermine was detected only from C. antiqua. These long linear polyamines are characteristic components of thermophilic bacteria. The detection from two species of Raphidophyceae indicates that the occurrence of long linear polyamines is not restricted to thermophilic microorganisms.
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effects of temperature and salinity on the growth of the red tide flagellates heterocapsa circularisquama dinophyceae and chattonella verruculosa Raphidophyceae
Journal of Plankton Research, 1997Co-Authors: Mineo Yamaguchi, Keizo Nagasaki, Yukihiko Matsuyama, Itakura Shigeru, Takuji Uchida, Ichiro ImaiAbstract:Growth responses of the red tide flagellates, Heterocapsa circularisquama (Dinophyceae) and Chattonella verruculosa (Raphidophyceae), were examined with 36 different combinations of temperature (5-3O°C) and salinity (10-35 PSU). Heterocapsa circularisquama did not grow at or below a temperature of 10°C. The maximum growth rate of H.circularisquama (13 divisions day1) was obtained with a combination of 30°C and 30 PSU. In contrast, C. verruculosa did not grow at 10 PSU and at temperatures of 25°C or more. The maximum growth rate of C. verruculosa (1.74 divisions day1) was obtained with a combination of 15°C and 25 PSU. A significant temperature-salinity inter- action on growth was found by factorial analysis. Based on the physiological characteristics obtained in the present study, these novel flagellates have a potential for future outbreaks of red tides in pre- viously unaffected waters.
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Virus-like particles in Heterosigma akashiwo (Raphidophyceae) : a possible red tide disintegration mechanism
Marine Biology, 1994Co-Authors: Keizo Nagasaki, Ichiro Imai, Masashi Ando, Shigeru Itakura, Yuzaburo IshidaAbstract:Electron microscopical observations on algal samples collected in 1992 in the middle or final stages of a red tide in Hiroshima Bay, Japan, revealed virus-like particles (VLPs) in the red tide alga Heterosigma akashiwo (Class Raphidophyceae). The host cells appeared moribund and the VLPs were located in and around the nuclear area. The VLPs were icosahedral, ca. 185 nm in diameter, and generated from the periphery of several viroplasms. VLPs were also observed in three other types of H. akashiwo-like cells, which were morphologically distinguishable from each other. The appearance of VLPs in the red tide alga could explain the dramatically rapid termination of this red tide.
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Densities of dormant cells of the red tide flagellate Heterosigma akashiwo (Raphidophyceae) in bottom sediments of northern Hiroshima Bay, Japan.
Bulletin of Japanese Society of Microbial Ecology, 1991Co-Authors: Ichiro Imai, Shigeru ItakuraAbstract:The distribution of dormant cells of the red tide flagellate Heterosigma akashiwo (Raphidophyceae) was investigated by the extinction dilution method in sediments of northern Hiroshima Bay where red tides of H. akashiwo occur almost every year. Densities of the dormant cells in sediment samples ranged from 56 to 5, 950 cells·cm-3 wet sediment in April 1987, and from 56 to 29, 300 cells·cm-3 in March 1989. No significant relationship was observed between the number of dormant cells of H. akashiwo and mud content of sediment sample. High density stations of the dormant cells in sediments appeared to coincide with the areas with high concentrations of vegetative cells in water columns during the red tide season.
Keizo Nagasaki - One of the best experts on this subject based on the ideXlab platform.
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Virus adsorption process determines virus susceptibility in Heterosigma akashiwo (Raphidophyceae)
Aquatic Microbial Ecology, 2006Co-Authors: Kenji Tarutani, Keizo Nagasaki, Mineo YamaguchiAbstract:We compared the adsorption kinetics of Heterosigma akashiwo virus clones 01 (HaV01) and 53 (HaV53) to several other H. akashiwo strains with differing viral susceptibility spectra. When a HaV strain was inoculated into its suitable host strain, only infectious virus particles (3 to 4% of direct count estimates) adsorbed to the host cells, and the adsorption coefficient was estimated to be 4.02 to 5.44 × 10 -8 ml min -1 ; in contrast, virus adsorption to an unsuitable host strain was not detected. This suggests that virus adsorption is an important first step in determining the sensitivity or resis- tance of H. akashiwo strains to viral infection, and that it determines the strain-specific host speci- ficity of HaV.
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effects of temperature and salinity on the growth of the red tide flagellates heterocapsa circularisquama dinophyceae and chattonella verruculosa Raphidophyceae
Journal of Plankton Research, 1997Co-Authors: Mineo Yamaguchi, Keizo Nagasaki, Yukihiko Matsuyama, Itakura Shigeru, Takuji Uchida, Ichiro ImaiAbstract:Growth responses of the red tide flagellates, Heterocapsa circularisquama (Dinophyceae) and Chattonella verruculosa (Raphidophyceae), were examined with 36 different combinations of temperature (5-3O°C) and salinity (10-35 PSU). Heterocapsa circularisquama did not grow at or below a temperature of 10°C. The maximum growth rate of H.circularisquama (13 divisions day1) was obtained with a combination of 30°C and 30 PSU. In contrast, C. verruculosa did not grow at 10 PSU and at temperatures of 25°C or more. The maximum growth rate of C. verruculosa (1.74 divisions day1) was obtained with a combination of 15°C and 25 PSU. A significant temperature-salinity inter- action on growth was found by factorial analysis. Based on the physiological characteristics obtained in the present study, these novel flagellates have a potential for future outbreaks of red tides in pre- viously unaffected waters.
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Isolation of a virus infectious to the harmful bloom causing microalga Heterosigma akashiwo (Raphidophyceae)
Aquatic Microbial Ecology, 1997Co-Authors: Keizo Nagasaki, Yamaguchi MAbstract:A virus infecting the harmful bloon~ causing microalga Heterosjgma akashiwo (Raphidophyceae) was isolated from the coastal water of Nomi Bay, Japan, In July 1996. The isolate caused lysis in 2 strains of H. akashiwo tested and numerous virus-like particles (VLPs) appeared in the lysed algal culture, whereas virus multiplication was not detected in the healthy culture of H. akashiwo without its inoculation. Thus, fulfilhng Koch's postulate, it was considered to be a virus and designated HaV (Heterosigma akashiwo virus) clone GSNOU-30 The virus particle is icosahedral, lacking a tail, and 202 * 6 nm (average * standard deviation) in diameter with an electron-dense roundish core that is distinct from the capsid. The vlrus stained positive with DAPI, indicating that it possesses a double stranded DNA genome. The virus proliferated in the protoplasm of the host cell as had previously been observed in H. akashiwo cells from a natural red tide population. The virus did not cause lysis of Chattonella antiqua, C. verruculosa or Fibrocapsa japonica (Raphidophyceae) as well as 15 strains of phytoplankton belonging to other classes. It is most noteworthy that 3 strains of H. akashjwo isolated from Hiroshima Bay, Japan, were resistant to GSNOU-30, suggesting that the viral infectivity is not species-specific but strain-specific. These results suggest that the virus is involved in the population dynamics of H. akashjwo, playing a role as a selector to increase genetic diversity of a host species.
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Chattonella and Fibrocapsa (Raphidophyceae): First Observation of, Potentially Harmful, Red Tide Organisms in Dutch Coastal Waters
Netherlands Journal of Sea Research, 1995Co-Authors: Engel G. Vrieling, Keizo Nagasaki, Yuzaburo Ishida, R.p.t. Koeman, Louis Peperzak, W. W. C. Gieskes, Marten VeenhuisAbstract:Species of the potentially toxic and red-tide-forming marine-phytoplankton genera Chattonella and Fibrocapsa (Raphidophyceae) were observed for the first time in 1991 in samples taken in Dutch coastal waters; they were again recorded and enumerated in the following years. Chattonella spp. cell numbers varied with the season, with a maximum in May or June in the Dutch Wadden Sea. Cell numbers of Chattonella and F. japonica Toriumi et Takano were up to 6.0 . 10(3) cells . dm(-3) in the Dutch Wadden Sea, except at one station in June 1993 when over 10(4) cells . dm(-3) Chattonella were counted. In May 1993, a minor bloom (over 2.0 . 10(5) cells . dm(-3)) was observed at a station in the southern central North Sea, 100 km northwest of the island of Terschelling. The potentially neurotoxic species Chattonella marina (Subrahmanyan) Hara et Chihara was identified and discriminated from morphologically related species within the class of Raphidophyceae by immunofluorescence. F. japonica could only be clearly identified in live samples; in fixed samples cell morphology was severely affected. The identification of this species was supported by the presence of mucocysts, structures that can be observed readily by optical and electron microscopy.
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Virus-like particles in Heterosigma akashiwo (Raphidophyceae) : a possible red tide disintegration mechanism
Marine Biology, 1994Co-Authors: Keizo Nagasaki, Ichiro Imai, Masashi Ando, Shigeru Itakura, Yuzaburo IshidaAbstract:Electron microscopical observations on algal samples collected in 1992 in the middle or final stages of a red tide in Hiroshima Bay, Japan, revealed virus-like particles (VLPs) in the red tide alga Heterosigma akashiwo (Class Raphidophyceae). The host cells appeared moribund and the VLPs were located in and around the nuclear area. The VLPs were icosahedral, ca. 185 nm in diameter, and generated from the periphery of several viroplasms. VLPs were also observed in three other types of H. akashiwo-like cells, which were morphologically distinguishable from each other. The appearance of VLPs in the red tide alga could explain the dramatically rapid termination of this red tide.
Carmelo R. Tomas - One of the best experts on this subject based on the ideXlab platform.
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Haemolytic activity within the species Fibrocapsa japonica (Raphidophyceae)
Harmful Algae, 2009Co-Authors: M. Karin De Boer, Carmelo R. Tomas, Engel G. Vrieling, Monika R. Tyl, Gemma Kulk, Gerd Liebezeit, Allison Lenzi, Jerome Naar, Marion Van RijsselAbstract:Strong haemolytic activity was observed for extracts of 15 Fibrocapsa japonica strains collected from different global regions. The EC(50) values ranged between 0.4 x 10(4) and 1.9 x 10(4) F.japonica cells ml(-1).The relationship between the haemolytic activity observed in the cell extracts and the amount and nature of polyunsaturated fatty acids (PUFAs)was investigated. Between 7% and 89% of the haemolytic activity could be attributed to the amount and toxicity of the PUFAs C18:4n3 (OTA), C20:5n3 (EPA), and C20:4n6 (AA). However, the higher the haemolytic activity of a strain the more it appeared to be caused by haemolytic compounds other than the PUFA's. The EC(50) of the extracts with the highest haemolytic activity strongly depended on light intensity and was in line with observations made on Chattonella marina. In the cell extracts of the strains studied brevetoxins were always below detection limits. For strains where 20-35% of the haemolytic activity was not caused by PUFAs, the concentration of these compounds was close to LC(50) values reported for fish. Overall the haemolytic activity of the F. japonica strains was in the range of known harmful microalgae. Therefore, PUFAs in combination with potent light dependent haemolytic compounds could be a major cause of ichthyotoxicity observed during F. japonica blooms. (C) 2009 Elsevier B.V. All rights reserved.
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Sterols and fatty acids of three harmful algae previously assigned as Chattonella.
Phytochemistry, 2008Co-Authors: José-luis Giner, Hui Zhao, Carmelo R. TomasAbstract:Abstract Sterol and fatty acid compositions were determined for three harmful algal species previously classified in the genus Chattonella (Raphidophyceae): the new genus Chloromorum toxicum (ex Chattonella cf. verruculosa), Verrucophora farcimen (Dictyochophyceae), previously Chattonella aff. verruculosa, and Verrucophora verruculosa (=Pseudochattonella verruculosa) previously Chattonella verruculosa. The major fatty acids of C. toxicum were 14:0, 16:0, 18:1n−9, 18:4n−3 and 20:5n−3, and those of the Verrucophora strains were. 14:0, 16:0, 18:0, 18:4n−3, 18:5n−3 and 22:6n−3. C. toxicum contained the 24β-ethyl sterols, poriferasterol and clionasterol, as its major sterols. For comparison, the stereochemistry of the 24-ethyl sterols of two raphidophytes, Chattonella marina and Heterosigma akashiwo, was determined to be 24α and 24β, respectively. Both Verrucophora strains contained the 27-nor sterol occelasterol as the only detected sterol. This was the first time occelasterol has been found in algae.
Toshihiko Kimura - One of the best experts on this subject based on the ideXlab platform.
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a red tide bloom of chattonella antiqua Raphidophyceae in the seto inland sea japan in 1987 analysed as changes in photosynthetic pigments determined by high performance liquid chromatography
Water Research, 1997Co-Authors: Kunio Kohata, Masataka Watanabe, Kazuo Yamanaka, Teru Ioriya, Toshihiko KimuraAbstract:Abstract A severe red-tide bloom of Chattonella antiqua (Raphidophyceae) was observed in the Seto Inland Sea (Japan) in summer 1987. The C. antiqua bloom was monitored from beginning to end at the 0, 5, 10, 15 m and bottom layers of a fixed sampling station almost every two days. Carotenoids and chlorophyllous pigments were measured by reversed-phase high-performance liquid chromatography before and during the bloom. Before the C. antiqua bloom, some diatoms were dominant, with a chlorophyll a (Chla) concentration ranging between 2 and 8 μg litre−1 at the surface. The maximum Chla concentration reached 27 μg litre−1 at the surface during the bloom, this being due to C. antiqua. Violaxanthin, which is a constituent carotenoid of C. antiqua, varied in line with cell concentration of the species. The relative abundance of C. antiqua was estimated as its Chla contribution to total Chla; the Chla contributions of Raphidophyceae, Bacillariophyceae and Dinophyceae were calculated from pigment ratios obtained by multiple regression analysis of pigment concentrations. The relative abundance of C. antiqua at the surface was calculated to be 0–16% before the bloom and 83–100% during the bloom.
Mineo Yamaguchi - One of the best experts on this subject based on the ideXlab platform.
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Virus adsorption process determines virus susceptibility in Heterosigma akashiwo (Raphidophyceae)
Aquatic Microbial Ecology, 2006Co-Authors: Kenji Tarutani, Keizo Nagasaki, Mineo YamaguchiAbstract:We compared the adsorption kinetics of Heterosigma akashiwo virus clones 01 (HaV01) and 53 (HaV53) to several other H. akashiwo strains with differing viral susceptibility spectra. When a HaV strain was inoculated into its suitable host strain, only infectious virus particles (3 to 4% of direct count estimates) adsorbed to the host cells, and the adsorption coefficient was estimated to be 4.02 to 5.44 × 10 -8 ml min -1 ; in contrast, virus adsorption to an unsuitable host strain was not detected. This suggests that virus adsorption is an important first step in determining the sensitivity or resis- tance of H. akashiwo strains to viral infection, and that it determines the strain-specific host speci- ficity of HaV.
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effects of temperature and salinity on the growth of the red tide flagellates heterocapsa circularisquama dinophyceae and chattonella verruculosa Raphidophyceae
Journal of Plankton Research, 1997Co-Authors: Mineo Yamaguchi, Keizo Nagasaki, Yukihiko Matsuyama, Itakura Shigeru, Takuji Uchida, Ichiro ImaiAbstract:Growth responses of the red tide flagellates, Heterocapsa circularisquama (Dinophyceae) and Chattonella verruculosa (Raphidophyceae), were examined with 36 different combinations of temperature (5-3O°C) and salinity (10-35 PSU). Heterocapsa circularisquama did not grow at or below a temperature of 10°C. The maximum growth rate of H.circularisquama (13 divisions day1) was obtained with a combination of 30°C and 30 PSU. In contrast, C. verruculosa did not grow at 10 PSU and at temperatures of 25°C or more. The maximum growth rate of C. verruculosa (1.74 divisions day1) was obtained with a combination of 15°C and 25 PSU. A significant temperature-salinity inter- action on growth was found by factorial analysis. Based on the physiological characteristics obtained in the present study, these novel flagellates have a potential for future outbreaks of red tides in pre- viously unaffected waters.