Bacillus thuringiensis (Bt) is an aerobic, Gram (+) and spore-forming entomopathogenic bacterium belonging to Bacillus cereus group together with Bacillus anthracis. Bt is the most widely and effectively used biological control agent against insect pests throughout the world. Following morphological and molecular characterization of the Bt SY56.3 isolate, Scanning Electron Microscopy (SEM) analysis was performed to determine the morphology of spore and parasporal crystal proteins (Cry) in this study. A small amount of lyophilized spore-crystalline mixture of Bt SY56.3 was put on a microscope slide containing a drop of distilled water and homogenized thoroughly. Then, it was dried at room temperature while quickly passing the slide 20 times over burner flame. The slide was then fixed onto the electron microscope holder with the aid of SC7620 Mini-Sputter Coater device. The slide was made conductive by coating with Golden Poladium (Au/Pd) for 30 seconds. The samples containing the Cry proteins in the range of 25-130 kDa were then placed in scanning electron microscope (LEO440) and visualized at 20kV. The size of crystal proteins ranged between 0.3-2 μm. It was observed that Bt SY56.3 isolate had cubic, bipyramidal, circular and irregular shaped Cry proteins. Present findings revealed that Bt SY56.3 could be used for biotechnological control applications because of different functions of these different Cry proteins.
Yılmaz et al. (Fri,) studied this question.