title: Molecular characterisation of Bacillus thuringiensis strain MEB4 highly toxic to the Mediterranean flour moth Ephestia kuehniella Zeller (Lepidoptera: Pyralidae).
abstract: BACKGROUND
  Cry2 proteins play an essential role in current Bacillus thuringiensis (Bt) applications and in the prevention of insect resistance to Cry1A toxins. This paper reports on the screening and characterisation of novel Bt strains harbouring effective cry2A-type genes and higher insecticidal activity to Ephestia kuehniella.
  
  
  RESULTS
  A total of 29 native Bt strains were screened to search for the potent strain against E. kuehniella. The plasmid pattern of the selected strains showed interesting variability. PCR-RFLP analysis of two amplified regions showed high sequence identity within the selected cry2A-type genes. SDS-PAGE and western blot analysis revealed the presence of Cry2Aa toxin only in the MEB4 and BLB240 strains. The activation of Cry2Aa protoxins by larval midgut juice, trypsin or chymotrypsin enzymes revealed significant differences in terms of proteolysis profiles. Interestingly, a 49 kDa band was detected in the proteolysis pattern of BLB240, suggesting the presence of a chymotrypsin cleavage site that might have affected its insecticidal activity. Further, bioassays demonstrated that MEB4 (103.08 ± 36 µg g(-1)) was more active than BLB240 (153.77 ± 45.65 µg g(-1)) against E. kuehniella.
  
  
  CONCLUSIONS
  Based on its potent insecticidal activity, the MEB4 strain could be considered to be an effective alternative agent for the control of E. kuehniella.
authors.affiliation: Laboratory of Plant Protection and Improvement (Biopesticides Team), Centre of Biotechnology, University of Sfax, Sfax, Tunisia.
authors.forename: Nouha
authors.initials: N
authors.lastname: Abdelmalek
authors.affiliation: Laboratory of Plant Protection and Improvement (Biopesticides Team), Centre of Biotechnology, University of Sfax, Sfax, Tunisia.
authors.forename: Sameh
authors.initials: S
authors.lastname: Sellami
authors.affiliation: Laboratory of Plant Protection and Improvement (Biopesticides Team), Centre of Biotechnology, University of Sfax, Sfax, Tunisia.
authors.forename: Asma
authors.initials: A
authors.lastname: Ben Kridis
authors.affiliation: Laboratory of Plant Protection and Improvement (Biopesticides Team), Centre of Biotechnology, University of Sfax, Sfax, Tunisia.
authors.forename: Slim
authors.initials: S
authors.lastname: Tounsi
authors.affiliation: Laboratory of Plant Protection and Improvement (Biopesticides Team), Centre of Biotechnology, University of Sfax, Sfax, Tunisia.
authors.forename: Souad
authors.initials: S
authors.lastname: Rouis
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000737:chemistry / Q000235:genetics*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics* / Q000494:pharmacology; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D004731:Endotoxins / Q000235:genetics* / Q000494:pharmacology; D006460:Hemolysin Proteins / Q000235:genetics* / Q000494:pharmacology; D007306:Insecticides / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects; D009036:Moths / Q000187:drug effects* / Q000254:growth & development; D010572:Pest Control, Biological; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; C030956:insecticidal crystal protein, Bacillus Thuringiensis
keywords: Bacillus thuringiensis; PCR-RFLP; cry2Aa gene; plasmid pattern; proteolysis