[Effect of mineral salts on exotoxin formation and productivity of a Bacillus thuringiensis culture]. / Vliianie mineral'nykh solei na ékzotoksinoobrazovanie i produktivnost' kul'tury Bacillus thuringiensis.

The effect of ten mineral salts on the productivity and toxin synthesis was studied in Bacillus thuringiensis IPM-1140. Exotoxin synthesis was stimulated by Zn2+, Mn2+ and NH4+ ions as well as by potassium phosphates. The direct correlation between the number of viable spores and the exotoxin accumulation was disordered at extreme salt concentrations. Optimal salt concentrations in the yeast-polysaccharide medium were found using the method of a fractional factor experiment, which made it possible to increase the productivity of the culture to 5 X 10(9) spores/ml and the yield of the exotoxin to 730 micrograms/ml. The thermoresistance and the entomopathogenic activity of crystals increased when B. thuringiensis IPM-1140 was grown in this medium.

[Possible means for increasing exotoxin synthesis by a Bacillus thuringiensis culture--the producer of bitoxibacillin]. / Vozmozhnye puti uvelicheniia sinteza ékzotoksina kul'turoi Bacillus thuringiensis--produtsentom bitoksibatsillina.

Various procedures were studied for obtaining Bacillus thuringiensis strains of serotype I which synthesized exotoxins. Mutant clones with elevated exotoxin synthesis could be selected by treating the cells with N-methyl-N-nitro-N-nitrosoguanidine. The frequency of (+) variant selection was from 17 to 12 X 10(-2). The clones of S and R types differed in the insecticide activity of the exotoxin. Its yield could be increased by optimizing the composition of growth media. The strain specificity of B. thuringiensis producing the exotoxin was assayed in terms of carbon and nitrogen requirements.

[Effect of gramicidin D on the exoprotease activity of Bacillus thuringiensis]. / Vliianie gramitsidina D na ékzoproteaznuiu aktivnost' Bacillus thuringiensis.

A treatment of Bacillus thuringiensis cells with gramicidine D in the medium containing the yeast and polysaccharides increases the lag-phase up to 12 h without a change of the rate during the logarithmic phase of the culture growth. The exoprotease activity of cells treated with gramicidine reaches a maximum value 4 h earlier in comparison with the control culture, and the activity level is increased 2-fold. At a concentration increasing the exoprotease activity, gramicidine was found to induce the permeability of Bac. thuringiensis membranes for potassium ions. An additional introduction of 250 mM KCl or NaCl into the medium inhibits only the exoprotease activity of cells treated with gramicidine. It is assumed that the ability of gramicidine to increase the exoprotease activity of Bac. thuringiensis may be due to a change in the intrabacterial ionic composition.