Insecticidal activity of the toxins from Bacillus thuringiensis subspecies kurstaki and tenebrionis adsorbed and bound on pure and soil clays

• Published in: Applied and Environmental Microbiology Vol. 61; no. 5; pp. 1786 - 1790
• Main Authors: Tapp, H. (New York University, New York, NY.), Stotzky, G
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01-05-1995
• Subjects: ADSORCION; ADSORPTION; BACILLUS THURINGIENSIS; Bacillus thuringiensis kurstaki; Bacillus thuringiensis tenebrionis; Bacteria; Biological and medical sciences; Biology; Biotechnology; CAOLINITA; Chrysomelidae; Coleoptera; Environment and pollution; Flowers & plants; FRACCIONES DEL SUELO; FRACTION DU SOL; Fundamental and applied biological sciences. Psychology; Genes; Genetically engineered organisms behavior (microorganisms, plants, animals); Industrial applications and implications. Economical aspects; INSECTICIDAS; INSECTICIDE; Insects; KAOLINITE; LEPTINOTARSA DECEMLINEATA; MANDUCA SEXTA; MONTMORILLONITA; MONTMORILLONITE; Poisons; Soils; TOXINAS; TOXINE; Recombinant microorganism; Chrysomelidae; Coleoptera; Toxicity; Insecta; Free form; Bacillaceae; Sphingidae; Bound form; Bacillus thuringiensis var. kurstaki; Bacillales; Leptinotarsa decemlineata; Bacteria; Transgenic plant; Release; Clay; Clay soil; Biological activity; Toxin; Adsorption; Larva; Arthropoda; Lepidoptera; Manduca sexta; Parasporal body; Invertebrata; Microbial insecticide
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/aem.61.5.1786-1790.1995

The release of transgenic plants and microorganisms expressing truncated genes from various subspecies of Bacillus thuringiensis that encode active insecticidal toxins rather than inactive protoxins could result in the accumulation of these active proteins in soil, especially when bound on clays and other soil particles. Toxins from B. thuringiensis subsp. kurstaki and B. thuringiensis subsp. tenebrionis, either free or adsorbed at equilibrium or bound on pure clay minerals (montmorillonite or kaolinite) or on the clay size fraction of soil, were toxic to larvae of the tobacco hornworm (Manduca sexta) and the Colorado potato beetle (Leptinotarsa decemlineata), respectively. The 50% lethal concentrations (LC50) of free toxins from B. thuringiensis subsp. kurstaki were higher than those of both bound and adsorbed complexes of these toxins with clays, indicating that adsorption and binding of these toxins on clays increase their toxicity in diet bioassays. The LC50 of the toxin from B. thuringiensis subsp. tenebrionis that was either free or adsorbed on montmorillonite were comparable, whereas the toxin bound on this clay had higher LC50 and the toxin bound on kaolinite had lower LC50 than when adsorbed on this clay. Results obtained with the clay size fraction separated from unamended soil or soil amended with montmorillonite or kaolinite were similar to those obtained with the respective pure clay minerals. Therefore, insecticidal activity of these toxins is retained and sometimes enhanced by adsorption and binding on clays