Identification of Bacillus thuringiensis isolated from different sources by Biolog GEN III system and Scanning Electron Microscopy

Hend Abdulhameed Hamedo



The present study aims to isolate and characterize Bacillus thuringiensis (Bt) strains isolated from different sources. These strains were subjected to morphological and biochemical characterization. The most active five isolates were presumptively confirmed as Bt strains. They were resistant to 8% NaCl, unable to survive at 50oC, motile and had haemolytic activity. The 5 isolates showed positive reaction to catalase test, methyl red test, arginine decarboxylation, citrate utilization and gave negative reactions to the oxidase test and indole test. All of them were also able to ferment glucose, sucrose, maltose, fructose, raffinose, dextrin, glycerol, pectin and gelatine whereas they could not ferment mannitol, arabitol, rhamnose, lactose, mannose or sorbitol. All isolates were Gram-positive and sensitive to Penicillin, Tobramycin, Bacitarcin and Amoxycillin/Clavulinic acid whereas they were resistant to Clindamycin, Nitrofuratoin, Candicidin and Chlramphenicol. The surface features of Bt spores were more clearly revealed with the scanning electron microscope. Bt spores have been described as cylindrical to ellipsoids in shape, surface smooth to very slightly ribbed and were covered with exosporium.

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