Leive L, Telesetsky S, Coleman W G, Carr D
Antimicrob Agents Chemother. 1984 May;25(5):539-44. doi: 10.1128/AAC.25.5.539.
The outer membrane of gram-negative cells excludes hydrophobic molecules and is responsible for the resistance of these cells to a number of dyes, detergents, and antibiotics. We describe a test for hydrophobic permeability in which a series of tetracyclines with various hydrophobicities are used. Normal Escherichia coli cells became more resistant as hydrophobicity was increased in this series, but mutants altered in outer membrane permeability remained susceptible. A mutant lacking all polysaccharide except 2-keto-3- deoxyoctonic acid in its lipopolysaccharide is virtually as susceptible to the hydrophobic drug 13- phenylmercapto -alpha-6- deoxytetracycline as to oxytetracycline (MIC 100 times lower than that of the wild type), and a mutant with another, as yet undefined outer membrane defect, acrA , also shows increased, although somewhat lesser, susceptibility (MIC 20 times lower than that of the wild type). Increased susceptibility to this tetracycline derivative is associated with greater fluorescence of the derivative when added to the cells, which we interpret as increased interaction of the derivative with hydrophobic domains, such as membranes, in the mutants. This series of tetracyclines may provide an assay for measuring the permeability of gram-negative organisms and their mutants to hydrophobic molecules.
革兰氏阴性菌的外膜可排除疏水分子，并使这些细菌对多种染料、去污剂和抗生素具有抗性。我们描述了一种用于检测疏水通透性的试验，其中使用了一系列具有不同疏水性的四环素。在该系列中，随着疏水性增加，正常大肠杆菌细胞的抗性增强，但外膜通透性发生改变的突变体仍易受影响。一种脂多糖中除2-酮-3-脱氧辛酸外所有多糖均缺失的突变体，对疏水药物13-苯巯基-α-6-脱氧四环素的敏感性几乎与对土霉素的敏感性相同（最低抑菌浓度比野生型低100倍），另一种具有尚未明确的外膜缺陷（acrA）的突变体也表现出敏感性增加，尽管程度稍小（最低抑菌浓度比野生型低20倍）。对这种四环素衍生物敏感性的增加与该衍生物添加到细胞时荧光增强有关，我们将此解释为该衍生物与突变体中诸如膜等疏水结构域的相互作用增强。这一系列四环素可用于检测革兰氏阴性菌及其突变体对疏水分子的通透性。
