Studies on Bacillus thuringiensis H-14 strains isolated in Egypt. VI. Correlation between specific plasmids and delta-endotoxin production
1994
Abdel-Hameed, A. | Carlberg, G. | Lindstrom, K. | El-Tayeb, O.M.
The crystal-producing (cry(+)) strains M1 and S128 of Bacillus thuringiensis H-14, and several noncrystal-producing (cry(-)) mutants derived from them, were analyzed for the presence of plasmid DNA in attempts to correlate delta-endotoxin production with the presence of a specific plasmid(s). Plasmid analysis of both parent strains revealed the presence of several plasmids in the size range of 3.2-130 megadalton (Mdal). The two strains were found to have identical plasmid profiles, except that strain M1 contained an additional plasmid of 68 Mdal. All the cry(-) mutants derived from the cry(+) parental strains had lost at least a 75 Mdal plasmid. On the other hand, plasmid analysis of cry(+) derivatives cured of one or more plasmids revealed that they all harbored the 75 Mdal plasmid. This correlation was further confirmed by a plasmid transfer experiment in which strain M1 transmitted the crystal-producing phenotype to a noncrystal-producing B. thuringiensis recipient. Agarose gel electrophoresis showed that the 75 Mdal plasmid was present in all the isolated cry(+) transcipients and absent in all the isolated cry(-) transcipients. These results demonstrate that the structural genes for the delta-endotoxin in the isolated strains of B. thuringiensis H-14 are borne on the 75 Mdal plasmid.
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