Binding of the protoxin and toxin proteins of Bacillus thuringiensis subsp. kurstaki on clay minerals
Authors: Venkateswerlu, G., Stotzky, G.
Journal, Volume, Year: Current Microbiology, volume 25:1-9, 1992
Adsorption and binding of protoxins (132 kDa) and toxins (66 kDa) from Btk on two types of clays were evaluated. Adsorption and binding was greater on montmorillonite (M) compared to kaolinite (K). Maximum adsorption occurred within 30 min and approximately 2- to 3-fold more toxin than protoxin was adsorbed on M and K. Desorption of protoxin and toxin occurred more easily from K compared to M. Adsorption was highest at the lower pH and decreased at pH increased. Binding did not appear to alter structure or eliminate insecticidal activity of protoxins and toxins. Clay-toxin complexes were toxic to third instar larvae of Trichoplusia ni.
The Btk toxins used in this study were Dipel or obtained from Abbott Laboratories. Experiments used pure montmorillonite and kaolinite. Experiments did not use natural soil or Bt toxins derived from transgenic crops.