title: Combinatorial effect of Bacillus amyloliquefaciens AG1 biosurfactant and Bacillus thuringiensis Vip3Aa16 toxin on Spodoptera littoralis larvae.
abstract: Spodoptera littoralis, one of the most serious and destructive agricultural pests in the world, is very susceptible to Vip3 toxin. In order to develop a new efficient bioinsecticide and to prevent the development of resistance by the target pest, insecticidal activity of biosurfactant produced by Bacillus amyloliquefaciens AG1 was evaluated against S. littoralis. Bioassays revealed the susceptibility of the first instar larvae of this pest to AG1 biosurfactant with an LC50of 245ng/cm2. Moreover, the histopathology examination of the larval midgut treated by AG1 biosurfactant showed vacuolization, necrosis and disintegration of the basement membrane. Binding experiments revealed that the AG1 biosurfactant recognized three putative receptors located in the brush border membrane vesicles of S. littoralis with sizes of 91, 72 and 64kDa. Competition assays using biotinylated metabolites indicated that AG1 biosurfactant and Vip3Aa16 toxin did not compete for the same S. littoralis receptors. When combined, AG1 biosurfactant and Vip3Aa16 showed an additive effect against S. littoralis larvae. These findings suggested that B. amyloliquefaciens AG1 biosurfactant could be a promising biocontrol agent to eradicate S. littoralis and to prevent resistance development by this pest.
authors.affiliation: Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia.
authors.forename: Saoussen
authors.initials: S
authors.lastname: Ben Khedher
authors.affiliation: Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia.
authors.forename: Hanen
authors.initials: H
authors.lastname: Boukedi
authors.affiliation: Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia.
authors.forename: Mariam
authors.initials: M
authors.lastname: Dammak
authors.affiliation: Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia.
authors.forename: Olfa
authors.initials: O
authors.lastname: Kilani-Feki
authors.affiliation: Laboratory of Anatomy and Pathological Cytology, P.O. Box 1507, 3029 Sfax, Tunisia.
authors.forename: Tahya
authors.initials: T
authors.lastname: Sellami-Boudawara
authors.affiliation: Department of Biology, Faculty of Sciences and Arts-Khulais, University of Jeddah, Saudi Arabia. Electronic address: mesratilobna@yahoo.com.
authors.forename: Lobna
authors.initials: L
authors.lastname: Abdelkefi-Mesrati
authors.affiliation: Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia.
authors.forename: Slim
authors.initials: S
authors.lastname: Tounsi
mesh_terms: D000818:Animals; D000069977:Bacillus amyloliquefaciens; D001426:Bacterial Proteins / Q000494:pharmacology*; D004357:Drug Synergism; D007306:Insecticides / Q000494:pharmacology; D007814:Larva / Q000187:drug effects; D010572:Pest Control, Biological / Q000379:methods*; D018411:Spodoptera / Q000187:drug effects*; D013501:Surface-Active Agents / Q000494:pharmacology*
chemical_list: D001426:Bacterial Proteins; D007306:Insecticides; D013501:Surface-Active Agents; C447139:Vip3A protein, Bacillus thuringiensis
keywords: Bacillus amyloliquefaciens AG biosurfactant; Histology; Putative binding receptors; Spodoptera littoralis; Toxicity; Vip3Aa16