Activity of spores and extracellular proteins from six Cry+ strains and a Cry- strain of Bacillus thuringiensis subsp. kurstaki against the western spruce budworm, Choristoneura occidentalis (Lepidoptera: Tortricidae)
Institute of Animal Systematics and Ecology, Russian Academy of Sciences, Siberian Division, 11 Frunze Str, Novosibirsk, Russia. Canadian Journal of Microbiology
(Impact Factor: 1.22).
06/2009; 55(5):536-43. DOI: 10.1139/w08-162
We characterized insecticidal activity of previously untested strains of Bacillus thuringiensis kurstaki belonging to two crystal serovars (K-1 and K-73) against the western spruce budworm (Choristoneura occidentalis Freeman 1967). By testing various components, we demonstrated that spores play a critical role in the pathogenesis of each strain. Spore-free crystals caused low mortality and purified spores were generally not toxic. The addition of spores to purified protoxin increased toxicity several hundred-fold, regardless of the parental strain from which the spores or protoxins were derived. The crystal and spore components did not account for full insecticidal activity of whole sporulated cultures owing to the toxicity of soluble proteins that are secreted during cell growth. We observed a marked difference in toxicity of secreted proteins between the K-1 and K-73 type strains, with the K-1 preparations causing much higher mortality, mass reduction, and inhibition of pupation. There was a consistent correlation between relative toxicity of secreted protein preparations and the presence and quantity of the Vip3A protein, suggesting that this protein contributes to the virulence of B. thuringiensis subsp. kurstaki in western spruce budworm larvae. However, other virulence factors have to be invoked to explain the synergizing effect of spores from both K-1 and K-73 strains on Cry protein toxicity.
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Available from: Enrique Vargas Osuna
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ABSTRACT: The toxicity of nine Bacillus thuringiensis Cry proteins against neonate Earias insulana larvae was tested using a mixture of crystals and spores. The mean lethal concentration (LC50) of Cry1Ac was 1.99 μg/ml. Cry1Fa, Cry1Ca, Cry1Ja and Cry2Aa were more active than Cry1Ac, with LC50 values of 0.22, 0.24, 0.29, 0.43 μg/ml, respectively. Cry1Da and Cry1Aa were considerably less active than Cry1Ac. The remaining proteins, Cry1Ba and Cry1Ab, displayed no activity. Relative potencies were also calculated. Cry1Ja and Cry1Fa were significantly more active (7.72 and 5.71 times, respectively) than Cry1Ac, while Cry1Ca was significantly (1.95 times) more active than Cry2Aa.
Available from: Amanda Lo
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ABSTRACT: Bacillus thuringiensis kurstaki is widespread in the environment, and the bacterium can be used as an insecticide. Bacteriophages, which are viruses that attack bacteria, are common in the environment as well. A potentially novel bacteriophage was isolated from Weber’s Cider Mill Farm in Proctor Lane, MD. The bacteriophage was then purified and characterized. The bacteriophage infected the bacterial host, B. thuringiensis kurstaki. Due to constant turbidity of plaques, findings revealed that a temperate bacteriophage, which enters the lysogenic cycle, had been isolated. Since plaques were invariably turbid, the bacteriophage was named Camo, which was derived from “camouflaged.” Moreover, further analysis of the head and tail components of the bacteriophage indicated that its morphotype is podoviridae.
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