Yatvin M B, Gipp J J, Klessig D R, Dennis W H
Radiat Res. 1986 Apr;106(1):78-88.
Hyperthermic sensitivities of Escherichia coli B/r and Bs-1 were determined for lag-, midlog-, and stationary-phase cells at 47, 48, and 49 degrees C. In both strains midlog-phase cells were strikingly more heat sensitive (100-fold greater killing after 4 h at 48 degrees C) than stationary-phase cells, with intermediate sensitivity for lag-phase cells. In contrast to the reported difference in the radiation sensitivity between these two strains, very little difference in heat sensitivity was seen. Patterns of fatty acid composition of both strains were very similar at each phase of growth. From midlog to stationary phase, 16:1 and 18:1 unsaturated fatty acids decrease from 16 and 30% to 0.5 and 3%, respectively, while the C17 and C19 cyclopropane fatty acids increase from 7 and 3% to 22 and 25%, respectively. Concomitant with these changes in fatty acid composition, substantially higher membrane microviscosity values were recorded for stationary-phase cells. Total membrane microviscosity was positively associated with the C17 and C19 cyclopropane fatty acid composition and with cell survival following hyperthermia. In contrast to hyperthermic sensitivity, radiation survival differences between B/r and Bs-1 are little affected by growth stage. We propose that these results are consistent with a critical influence of membrane lipids on cellular hyperthermic sensitivity and further that the target sites for radiation and hyperthermia are different in these cells.
在47、48和49摄氏度下，测定了大肠杆菌B/r和Bs-1在迟缓期、对数中期和稳定期细胞的热敏感性。在这两种菌株中，对数中期细胞的热敏感性明显高于稳定期细胞（48摄氏度下4小时后杀灭率高100倍），迟缓期细胞的敏感性介于两者之间。与报道的这两种菌株辐射敏感性的差异相反，热敏感性差异很小。两种菌株在每个生长阶段的脂肪酸组成模式非常相似。从对数中期到稳定期，16:1和18:1不饱和脂肪酸分别从16%和30%降至0.5%和3%，而C17和C19环丙烷脂肪酸分别从7%和3%增至22%和25%。伴随着这些脂肪酸组成的变化，稳定期细胞的膜微粘度值显著更高。总膜微粘度与C17和C19环丙烷脂肪酸组成以及热疗后的细胞存活率呈正相关。与热敏感性不同，B/r和Bs-1之间的辐射存活率差异受生长阶段的影响很小。我们认为，这些结果与膜脂对细胞热敏感性的关键影响一致，进一步表明这些细胞中辐射和热疗的靶点不同。
