Search for natural isolates of Bacillus thuringiensis for development of ecologically friendly biologicals

Intensification of agriculture determined the use of biopesticides for plant protection against harmful insects and phytopathogens. Currently, the biological preparations derived from the entomopathogenic bacterium Bacillus thuringiensis are of considerable interest since they have high specificity of action, safety for humans, warm-blooded animals, beneficial insects and the environment. High adaptive capacity of B. thuringiensis underlies its widespread distribution in nature. This paper represents the results of the screening for novel B. thuringiensis isolates from the natural substrates in the Leningrad region. There were 30 samples of substrates collected including soil, potato leaves, sick and dead insects. These samples were colony-purified on the fish agar medium. Based on morphology, 86 candidate colonies were selected from 3 500 colonies analyzed. Aniline Black staining coupled with optical microscopy demonstrated that 12 out of 86 isolates formed crystalline endotoxins of different shapes along with the spores...