Silver-resistant mutants of Escherichia coli display active efflux of Ag+ and are deficient in porins
Silver-resistant mutants of Escherichia coli display active efflux of Ag+ and are deficient in porins
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DOI：
10.1128/jb.179.19.6127-6132.1997
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发表时间：
1997-10-01
影响因子：
3.2
通讯作者：
Williams, KE
中科院分区：
文献类型：
--
作者：
Li, XZ;Nikaido, H;Williams, KE
通过将大肠杆菌的银敏感临床菌株逐步暴露于银硝酸盐或银磺胺嘧啶，选择银抗性突变体，其中两种菌株不含任何质粒。这些突变株对两种化合物都表现出完全的交叉抗性，它们对头孢菌素和HgCl_2表现出低水平的交叉抗性，但对其他重金属没有交叉抗性。抗Ag突变株对头孢菌素的外膜（OM）通透性降低，并且所测试的五个抗性突变株都缺乏主要孔蛋白，或者OmpF或OmpF + OmpC。实验室菌株K-12和B/r的充分研究的OmpF-和/或OmpC-缺陷突变体对任何一种银化合物都不具有抗性。抗性菌株积累的（AgNO 3）-Ag-110 m比亲本菌株少四倍，用羰基氰间氯苯腙处理细胞增加了Ag敏感株和抗Ag株的Ag积累，这表明即使是野生型Ag敏感株也具有内源性Ag外排活性，其在抗Ag突变体中发生在较高水平。加入葡萄糖作为能量来源，激活了饥饿细胞的Ag外排。结果表明，主动外排，推测由染色体基因编码，可能在银抗性中起主要作用，这可能是协同增强OM渗透性的降低。
Silver-resistant mutants were selected by stepwise exposure of silver-susceptible clinical strains of Escherichia coli, two of which did not contain any plasmids, to either silver nitrate or silver sulfadiazine. These mutants showed complete cross-resistance to both compounds, They showed low-level cross-resistance to cephalosporins and HgCl2 but not to other heavy metals, The Ag-resistant mutants had decreased outer membrane (OM) permeability to cephalosporins, and all five resistant mutants tested were deficient in major porins, either OmpF or OmpF plus OmpC, However, the well-studied OmpF- and/or OmpC-deficient mutants of laboratory strains K-12 and B/r were not resistant to either silver compound, Resistant strains accumulated up to fourfold less (AgNO3)-Ag-110m than the parental strains, The treatment of cells with carbonyl cyanide m-chlorophenylhydrazone increased Ag accumulation in Ag-susceptible and -resistant strains, suggesting that even the wild-type Ag-susceptible strains had an endogenous Ag efflux activity, which occurred at higher levels in Ag-resistant mutants. The addition of glucose as an energy source to starved cells activated the efflux of Ag, The results suggest that active efflux, presumably coded by a chromosomal gene(s), may play a major role in silver resistance, which is likely to be enhanced synergistically by decreases in OM permeability.