苏云金芽孢杆菌工程菌伴孢晶体的形态发生

苏云金芽孢杆菌在有帮助蛋白存在的情况下杀虫晶体蛋白获得了超量表达。通过透射电镜观察了Cry1Ac超量表达工程菌伴孢晶体的形态发生以及不同芽孢发育时期的晶体形态变化。结果表明，该工程菌的伴孢晶体在细胞不对称分裂的隔膜形成前就已出现，而且晶体发生的部位与芽孢无关。但晶体在形成初期往往靠近母细胞膜。观察结果还表明，大量表达的晶体蛋白不能马上参与到晶体合成，晶体形成的最佳时期是芽孢皮层形成期。母细胞大量液泡的产生与消失可能与晶体形成有关。此外，在超量表达工程菌中，Cry1Ac蛋白能在一个细胞内形成多个伴孢晶体，这在天然菌株中是罕见的。

The Morphological Development of Parasporal Crystals of An Engineered Strain of Bacillus thuringiensis

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.