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The impact of the Bacillus subtilis SPB1 biosurfactant on the midgut histology of Spodoptera littoralis (Lepidoptera: Noctuidae) and determination of its putative receptor

Ghribi, Dhouha, Abdelkefi-Mesrati, Lobna, Boukedi, Hanen, Elleuch, Mouna, Ellouze-Chaabouni, Semia, Tounsi, Slim
Journal of invertebrate pathology 2012 v.109 no.2 pp. 183-186
Bacillus subtilis, Bacillus thuringiensis, Spodoptera littoralis, biosurfactants, brush border membrane vesicles, cotton, epithelial cells, histology, histopathology, insecticidal properties, larvae, leaves, lethal concentration 50, lipopeptides, midgut, molecular weight, toxicity, toxins
SPB1 is a Bacillus subtilis strain producing a lipopeptide biosurfactant. The insecticidal activity of this biosurfactant was evaluated against the Egyptian cotton leaf worm (Spodoptera littoralis). It displayed toxicity with an LC₅₀ of 251ng/cm². The histopathological changes occurred in the larval midgut of S. littoralis treated with B. subtilis SPB1 biosurfactant were vesicle formation in the apical region, cellular vacuolization and destruction of epithelial cells and their boundaries. Ligand-blotting experiments with S. littoralis brush border membrane vesicles showed binding of SPB1 biosurfactant to a protein of 45kDa corresponding to its putative receptor. The latter differs in molecular size from those recognized by Bacillus thuringiensis Vip3A and Cry1C toxins, commonly known by their activity against S. littoralis. This result wires the application of B. subtilis biosurfactant for effective control of S. littoralis larvae, particularly in the cases where S. littoralis will develop resistance against B. thuringiensis toxins.