Enterotoxin productions of Bacillus cereus isolated from soil samples and of Bacillus thurigiensis isolated from vegetables
2001
Kikuta, H. (Rakuno Gakuen Univ., Ebetsu, Hokkaido (Japan)) | Miyaji, Y. | Ikegami, Y.
The microbial insecticide Bacillus thuringiensis has been isolated from soil in the forest, parks and fields associated with human living space. In these experiments, enterotoxin productions of Bacillus cereus isolated from soil and of B. thuringiensis isolated from vegetables were investigated in relation to their bearing on the human environment. 1. In experiments to determine the number of viable cells of B. thuringiensis in various soils, no B. thuringiensis cells were present in soil sampled from the forest 14 days after spraying, nor were any B. thuringiensis cells found in soil sampled from the field 3 days after spraying. This result suggests that B. thuringiensis is eradicated over time or that only a small population survives in the long term, depending on the properties of the soil and on related conditions. 2. Spore-bearing bacteria of enterotoxin producer was found in 24.2% of the forest soil, 7. 4% of the park soil, and 3. 3% of the field soil. This suggests the possibility of food contamination due to spore-bearing bacteria in the soil. 3. B. thuringiensis strains were isolated from vegetables obtained from the market, and experiments were conducted to identify the enterotoxin productions in the various strains. The rate of B. thuringiensis isolation from the vegetables was 1.1%. This rate is comparable to that of wild-type B. thuringiensis.
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