[Influence of carbon sources on the biological activity and morphology of Bacillus thuringiensis parasporal crystals].

The influence of the carbon source on biological activity and morphological properties of the parasporal crystals of Bacillus thuringiensis subsp. kurstaki cultivated on three different media has been studied. Biological activity of delta-endotoxins contained in crystals was tested according to their impact on insects and microorganisms. Variations in carbon sources composition resulted in changes of biological activity and morphology of crystals, caused by alterations in synthesis rate of various delta-endotoxins contained in the crystals. Variations in the content of a certain carbon source (e.g. starch) in the medium produced no effect on the crystals properties, and the content variations of the delta-endotoxins content was proportional to the producer biomass. Control of the antibacterial effect of delta-endotoxins allows a valid evaluation of their biological activity under various growth conditions as well as comparison of the biological potential of entomopathogenic chemicals for plant protection containing delta-endotoxins with different specificity of insecticidal activity.