Transfer of Bacillus thuringiensis plasmids coding for delta-endotoxin among strains of B. thuringiensis and B. cereus.

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Abstract
The recently discovered high-frequency transfer of plasmids between strains of B. thuringiensis was used to study the genetic relationship between plasmids and production of the insecticidal .delta.-endotoxin crystal. Three strains of B. thuringiensis transmitted the Cry+ (crystal-producing) phenotype to Cry- (acrystalliferous) B. thuringiensis recipients. Agarose gel electrophoresis showed that 1 specific plasmid from each donor strain was always present in Cry+ transcipients. The size of the transmissible crystal-coding plasmid varied with the donor strain, being 75 MDal (megadaltons) in size in HD-2, 50 MDal in HD-73 and 44 MDal in HD-263. Immunological analysis showed the Cry+ transcipients to be hybrid strains, having flagella of the recipient serotype and crystals of the donor serotype. The structural genes for the .delta.-endotoxin are evidently plasmid borne. Crystal-coding plasmids also transferred into 2 strains of the related species B. cereus and yielded transcipients that produced crystals of the same antigenicity as the donor strain.