Hardaway K L, Buller C S
J Bacteriol. 1979 Jan;137(1):62-8. doi: 10.1128/jb.137.1.62-68.1979.
Treatment of Escherichia coli K-12 strain S15, containing a normal amount of phospholipase A, with ethylenediaminetetraacetate (EDTA) resulted in an increase in sensitivity of the organism to actinomycin D. Strain S17, a mutant deficient in both detergent-resistant phospholipase A and detergent-sensitive phospholipase A, was considerably less sensitive to the antibiotic after the treatment. Both strains released lipopolysaccharide after EDTA treatment, indicating that this outer membrane component alone is not the barrier to actinomycin in these organisms. The phospholipase A-deficient strain released less alkaline phosphatase, a periplasmic enzyme. EDTA treatment of S15 resulted in the accumulation of free fatty acids, indicative of phospholipase A activation. Cells briefly treated with EDTA regained the barrier to actinomycin when incubated in growth media, and the cessation of the accumulation of free fatty acids was in approximate temporal agreement with restoration of the barrier. Cells in which phospholipase A was activated by brief exposure to EDTA synthesized relatively more phosphatidylethanolamine than did untreated cells in the initial period after dilution into growth media. These experiments suggest that the EDTA-induced loss of outer membrane barrier function of E. coli K-12 is mediated through the activation of phospholipase A.
用乙二胺四乙酸（EDTA）处理含有正常量磷脂酶A的大肠杆菌K-12菌株S15，导致该生物体对放线菌素D的敏感性增加。菌株S17是一种对耐去污剂磷脂酶A和对去污剂敏感的磷脂酶A均缺乏的突变体，处理后对该抗生素的敏感性明显较低。两种菌株在EDTA处理后均释放出脂多糖，这表明仅这种外膜成分不是这些生物体中放线菌素的屏障。缺乏磷脂酶A的菌株释放出较少的碱性磷酸酶，一种周质酶。用EDTA处理S15导致游离脂肪酸的积累，这表明磷脂酶A被激活。当在生长培养基中孵育时，用EDTA短暂处理的细胞恢复了对放线菌素的屏障作用，并且游离脂肪酸积累的停止与屏障的恢复在时间上大致一致。在稀释到生长培养基后的初始阶段，通过短暂暴露于EDTA而激活磷脂酶A的细胞比未处理的细胞合成相对更多的磷脂酰乙醇胺。这些实验表明，EDTA诱导的大肠杆菌K-12外膜屏障功能丧失是通过磷脂酶A的激活介导的。
