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Pesticide Toxicology Laboratory

ISU Entomology / Pesticide Toxicology Laboratory / Biodegradation and insecticidal activity of the toxin from Bacillus thuringiensis subsp. kurstaki bound on complexes of montmorillonite-humic acids-Al hydroxypolymers

Biodegradation and insecticidal activity of the toxin from Bacillus thuringiensis subsp. kurstaki bound on complexes of montmorillonite-humic acids-Al hydroxypolymers

Authors: Crecchio, C., Stotzky, G.
Journal, Volume, Year: Soil Biology and Biochemistry, volume 33:573-581, 2001
Summary

Adsorption and binding of Btk toxins on montmorillonite-humic acid-Al hydroxypolymers, biodegradation, and insecticidal activity of bound Btk toxins were evaluated. Maximal adsorption occurred within 8 hours with 70% adsorbed within the first hour. Adsorption was greatest between pH 5 and 6 and decreased as pH increased. Less than 2% of Btk toxin was desorbed after washing with ddH2O and 1 M NaCl. Adsorbed Btk toxin was resistant to utilization by microorganisms and did not support the microbial growth. The LC50 values were lower for the adsorbed Btk toxins than free for toxins.

Comments

Although this is an artificial environment, organomineral complexes more similar to natural soil than previously used purified clays and humic acid were used. The Btk toxins used in this study were derived from Dipel technical powder. Insecticidal activity was determined by adding dilutions of bound and free Btk toxin onto tobacco hornworm medium. Ecological relevance was not established.