Abstract:

The germination of dormant spores of Bacillus species is the first crucial step in the return of spores to vegetative growth. Some members of Bacillus species cause serious diseases in livestock and humans. Elucidation of the germination process is essential to understand their pathogenesis and life cycle. To determine the role of plasmid pHT73 in nutrient-induced germination, the conditions for germination of Bacillus thuringiensis HD-73 was optimized. The optimum germination buffer was NaH2PO4 （10 mmol·L^-1） and NaC1 （100 mmol·L^-1） and pH 7.2. The optimum temperature was 37℃. Comparing the germination rate between HD-73 strain and HD-73- mutant spores, which was based on the optimum germination conditions, germination rate of HD-73- spores was twice of that of HD-73 in the pathways of inosine （1 mmol·L^-1） / Asp （100 mmol·L^-1） and inosine （1 mmol·L^-1） / Glu （100 mmol·L^-1））. This result supported that the plasmid pHT73 contained the germination genes which partly blocked those two pathways, because HD-73- was cured of plasmid pHT73 which contained crylAC gene.

Key words: Bacillus thuringiensis , plasmid pHT73, germination, HD-73

摘要：

芽孢的萌发是芽孢杆菌从芽孢成长为营养体的第一步。在芽孢菌属中，有些菌株对人畜具有致病性。研究芽孢萌发过程对解析其致病性和生理功能至关重要。本文优化了苏云金芽孢杆菌（Bacillus thuringiensis，Bt）芽孢的萌发条件，确定芽孢萌发的适宜条件为：缓冲液为NaH2PO4（10mmol·L^-1）与NaCl（100mmol·L^-1）的混合物、pn值为7．2、萌发温度为37℃，萌发剂为肌苷或L-丙氨酸（1mmol·L^-1）与其它单一氨基酸（100mmol·L^-1，除酪氨酸和色氨酸为1mmol·L^-1）组成的混合物；利用该萌发条件，检测了苏云金芽孢杆菌菌株HD-73及其无晶体突变株HD-73^-在利用不同氨基酸途径中的芽孢萌发率差异，发现缺失质粒pHT73的无晶体突变株HD-73^-在肌苷与天冬氨酸和肌苷与谷氨酸为营养萌发剂的条件下，萌发率明显高于菌株HD-73，说明在质粒pHT73上可能存在对这两种途径起负调控作用的相关基因。

关键词: 苏云金芽孢杆菌 质粒pHT73 芽孢萌发 萌发条件 HD-73菌株