title: Molecular characterization and genetic diversity of insecticidal crystal protein genes in native Bacillus thuringiensis isolates.
abstract: The Western Ghats of Karnataka natural ecosystem are among the most diverse and is one of the eight hottest hotspots of biological diversity in the world, that runs along the western part of India through four states including Karnataka. Bacillus thuringiensis (Bt) strains were isolated from soils of Western Ghats of Karnataka and characterized by molecular and analytical methods as a result of which 28 new Bt-like isolates were identified. Bt strains were isolated from soil samples using sodium acetate selection method. The morphology of crystals was studied using light and phase contrast microscopy. Isolates were further characterized for insecticidal cry gene by PCR, composition of toxins in bacterial crystals by SDS-PAGE cloning, sequencing and evaluation of toxicity was done. As a result 28 new Bt-like isolates were identified. Majority of the isolates showed the presence of a 55 kDa protein bands on SDS-PAGE while the rest showed 130, 73, 34, and 25 kDa bands. PCR analysis revealed predominance of Coleopteran-active cry genes in these isolates. The variations in the nucleotide sequences, crystal morphology, and mass of crystal protein(s) purified from the Bt isolates revealed genetic and molecular diversity. Three strains containing Coleopteran-active cry genes showed higher activity against larvae Myllocerus undecimpustulatus undatus Marshall (Coleoptera: Curculionidae) than B. thuringiensis subsp. Morrisoni. Results indicated that Bt isolates could be utilized for bioinsecticide production, aiming to reduce the use of chemical insecticide which could be useful to use in integrated pest management to control agriculturally important pests for sustainable crop production.
authors.affiliation: Division of Biotechnology, Indian Institute of Horticultural Research (IIHR), Hessarghatta Lake Post, Bangalore, 560089, Karnataka, India. clintonbio@gmail.com
authors.forename: H M
authors.initials: HM
authors.lastname: Mahadeva Swamy
authors.forename: R
authors.initials: R
authors.lastname: Asokan
authors.forename: Riaz
authors.initials: R
authors.lastname: Mahmood
authors.forename: S N
authors.initials: SN
authors.lastname: Nagesha
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000166:cytology / Q000235:genetics* / Q000302:isolation & purification*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000633:toxicity; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D004731:Endotoxins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000633:toxicity; D014644:Genetic Variation; D006460:Hemolysin Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000633:toxicity; D007194:India; D007814:Larva / Q000187:drug effects; D008853:Microscopy; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D016019:Survival Analysis; D048889:Weevils / Q000187:drug effects / Q000254:growth & development
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis