Asporogenous Bacillus thuringiensis Mutant Producing High Yields of delta-Endotoxin.

An asporogenous Bacillus thuringiensis subsp. kurstaki strain IK mutant, strain 290-1, which produced high yields of delta-endotoxin, was obtained by ethyl methane sulfonate treatment of a spore suspension. The mutant strain produced about the same amount of delta-endotoxin as that produced by the parent strain, but 10 to 10 cells did not form any detectable dormant spores.