Lubitz W, Harkness R E, Ishiguro E E
J Bacteriol. 1984 Jul;159(1):385-7. doi: 10.1128/jb.159.1.385-387.1984.
Escherichia coli VC30 is a temperature-sensitive mutant which is defective in autolysis. Strain VC30 lyses at 30 degrees C when treated with beta-lactam antibiotics or D-cycloserine or when deprived of diaminiopimelic acid. The same treatments inhibit growth of the mutant at 42 degrees C but do not cause lysis. Strain VC30 was used here to investigate the mechanism of host cell lysis induced by bacteriophage phi X 174. Strain VC30 was transformed with plasmid pUH12, which carries the cloned lysis gene (gene E) of phage phi X174 under the control of the lac operator-promoter, and with plasmid pMC7, which encodes the lac repressor to keep the E gene silent. Infection of strain VC30(pUH12)(pMC7) with phage phi X174 culminated in lysis at 30 degrees C. At 42 degrees C, intracellular phage development was normal, but lysis did not occur unless a temperature downshift to 30 degrees C was imposed. Similarly, induction of the cloned phi X174 gene E with isopropyl-beta-D-thiogalactoside resulted in lysis at 30 degrees C but not at 42 degrees C. Temperature downshift of the induced culture to 30 degrees C resulted in lysis even in the presence of chloramphenicol. These results indicate that host cell lysis by phage phi X174 is dependent on a functional cellular autolytic enzyme system.
大肠杆菌VC30是一种温度敏感型突变体，其自溶存在缺陷。当用β-内酰胺抗生素或D-环丝氨酸处理，或缺乏二氨基庚二酸时，菌株VC30在30℃会发生裂解。相同处理会抑制该突变体在42℃的生长，但不会导致裂解。这里使用菌株VC30来研究噬菌体φX174诱导宿主细胞裂解的机制。菌株VC30用质粒pUH12进行转化，该质粒在乳糖操纵子-启动子的控制下携带噬菌体φX174的克隆裂解基因（基因E），还用质粒pMC7进行转化，该质粒编码乳糖阻遏物以使E基因保持沉默。用噬菌体φX174感染菌株VC30(pUH12)(pMC7)最终在30℃导致裂解。在42℃时，细胞内噬菌体发育正常，但除非温度降至30℃，否则不会发生裂解。同样，用异丙基-β-D-硫代半乳糖苷诱导克隆的φX174基因E在30℃导致裂解，但在42℃不会。即使存在氯霉素，将诱导培养物的温度降至30℃也会导致裂解。这些结果表明噬菌体φX174引起的宿主细胞裂解依赖于功能性的细胞自溶酶系统。
