The Morphological Development of Parasporal Crystals of An Engineered Strain of Bacillus thuringiensis
苏云金芽孢杆菌工程菌伴孢晶体的形态发生

Transmission electron microscope was used to observe the morphological development of parasporal crystals of an engineered Bacillus thuringiensis strain of high Cry1Ac productivity with the presence of helper protein P20, in control with the P20 absent strain. Our results showed that in P20 present strain Cry1Ac crystallization occurred in the plasma of mother cells before septum formation and crystal location in mother cell has no definite relation with spore. However, they usually attached to the plasma membrane of the mother cells by one side. Moreover, the phase of cortex formation proved to be the best time to crystal growing, which was several hours later after Cry1Ac protoxin reached the highest concentration in plasma. In addition, vacuoles in mother cells of both strains might have some relations with crystal development, which appearing in stationary phase and disappearing with crystal growth. Relative to the P20 absent control, crystals were much larger and multiple crystals of Cry1Ac were usually observed in one cell of the P20 present strain. This is rarely reported in wild type strains with the expression of single Cry protein.