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Electroporation was used as a method to transform intact cells of Bacillus thuringiensis and B. cereus. With our optimized method a range of plasmid vectors could be transformed into strains of B. thuringiensis at frequencies of up to 10(7) transformants/micrograms DNA. This high frequency allows cloning experiments to be done directly in B. thuringiensis. A bifunctional vector capable of replicating in Escherichia coli and in Bacillus spp. was constructed. The kurhd1 protoxin gene was cloned into this shuttle vector to produce plasmid pX193, then transformed into B. thuringiensis HD1 cryB and B. cereus 569K. The cloned protoxin gene was expressed in sporulating cultures of both strain HD1 cryB (pX193) and 569K (pXI93), producing crystal protein active in biotests against larvae of Heliothis virescens. This demonstrates the usefulness of the electroporation method for the introduction of cloned toxin genes, in either their native or modified form, into a variety of host strains.

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Streptomyces glaucescens ETH 22794 produced a variety of antibiotic substances. Besides low molecular weight antibiotics like hydroxystreptomycin and the tetracenomycins, this strain excreted glaucescin, a high molecular weight product with bacteriocin-like properties. In plate tests the antagonism of glaucescin against Streptomyces canadiensis was masked by the large inhibition zone caused by the tetracenomycins. Glaucescin activity was revealed when a tetracenomycin-resistant mutant of S. canadiensis NRRL 3155 was used as an indicator. Glaucescin was produced on complex and minimal solid and liquid media. It was not inducible by mitomycin C. The killing activity of glaucescin was thermolabile and resistant to DNAase, RNAase, various proteinases, and lipase. Its apparent molecular weight was estimated as 196000 by gel filtration and glycerol gradient centrifugation. Glaucescin preferentially killed outgrowing spores of S. canadiensis. Resting spores and mycelium were considerably less sensitive to the inhibitor, and adsorption of glaucescin by S. canadiensis paralleled sensitivity. The activity spectrum of the bacteriocin was restricted to spore-forming Actinomycetales. Non spore-forming nocardiae and a variety of Grampositive and Gram-negative bacteria were resistant to glaucescin.