Characterization of Bacillus thuringiensis Having Insecticidal Effects AgainstLarvae of Musca domestica

The entomopathogenic bacterium Bacillusthuringiensis is the most widely used biopesticide. Insecticidalproteins, coded by genes located in plasmids, form typicalparasporal, crystalline inclusions during sporulation. We isolateda Bacillus thuringiensis strain having insecticidal activityagainst larvae of the house fly (M. domestica) from the soilsat a pig farm in Korea, and named it Bacillus thuringiensisSM. The culture filtrate from Bacillus thuringiensis SM showedstrong lethality (83.3%) against M. domestica larvae. Theparasporal crystal is enclosed within the spores' outermostenvelope, as determined by transmission electron microscopy,and exhibited a bipyramidal form. The crystal proteins ofstrain SM consisted of five proteins with molecular weightsof approximately ~130, ~80, ~68, ~42, and ~27 kDa on a10% SDS-PAGE (major band, a size characteristic of Cryprotein). Examination of antibiotic resistance revealed thatthe strain SM showed multiple resistant. The strain SM had atleast three different plasmids with sizes of 6.6, 9.3, and 54 kb.Polymerase chain reactions (PCRs) revealed the presence ofcry1, cry4A2, and cry11A1 genes in the strain SM. The cry1gene profile of the strain SM appeared in the three respectiveproducts of 487 bp [cry1A(c)], 414 bp [cry1D], and 238 bp[cry1A(b)]. However, the strain SM has not shown the cry4A2and cry11A1 genes. In in vivo toxicity assays, the strain SMshowed high toxicity on fly larvae (M. domestic) [with LC50of 4.2 mg/ml, LC90 of 8.2 mg/ml]. KCI Citation Count: 4