Deletion by in vivo recombination shows that the 28-kilodalton cytolytic polypeptide from Bacillus thuringiensis subsp. israelensis is not essential for mosquitocidal activity.
The cytA gene encoding the 28-kDa polypeptide of Bacillus thuringiensis subsp. israelensis crystals was disrupted in the 72-MDa resident plasmid by in vivo recombination, thus indicating that homologous recombination occurs in B. thuringiensis. The absence of the 28-kDa protein in B. thuringiensis did not affect the crystallization of the other toxic components of the parasporal body (68-, 125-, and 135-kDa polypeptides). The absence of the 28-kDa protein abolished the hemolytic activity of B. thuringiensis subsp. israelensis crystals. However, the mosquitocidal activity of the 28-kDa protein-free crystals did not differ significantly from that of the wild-type crystals when tested on Aedes aegypti and Culex pipiens larvae. The 28-kDa protein contributed slightly to the toxicity to Anopheles stephensi larvae. This indicates that the 28-kDa protein is not essential for mosquitocidal activity, at least against the three species tested.
Unité de Biochimie Microbienne, URA 1300 CNRS, Paris, France.
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Charles
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D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics / Q000472:pathogenicity*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics*; D001427:Bacterial Toxins; D015139:Blotting, Southern; D015153:Blotting, Western; D002872:Chromosome Deletion; D009033:Culicidae; D004591:Electrophoresis, Polyacrylamide Gel; D004731:Endotoxins; D006460:Hemolysin Proteins; D006461:Hemolysis; D010455:Peptides / Q000494:pharmacology; D010957:Plasmids; D011995:Recombination, Genetic; D015183:Restriction Mapping; D014170:Transformation, Genetic
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D010455:Peptides; C030956:insecticidal crystal protein, Bacillus Thuringiensis