PhoP-PhoQ homologues in Pseudomonas aeruginosa regulate expression of the outer-membrane protein OprH and polymyxin B resistance
PhoP-PhoQ homologues in Pseudomonas aeruginosa regulate expression of the outer-membrane protein OprH and polymyxin B resistance
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DOI：
10.1046/j.1365-2958.1999.01600.x
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发表时间：
1999-10-01
影响因子：
3.6
通讯作者：
Hancock, REW
中科院分区：
文献类型：
--
作者：
Macfarlane, ELA;Kwasnicka, A;Hancock, REW
快速适应环境挑战对于许多细菌物种的生存至关重要，最终往往由两部分调节系统有效介导。铜绿假单胞菌对 Mg2+ 饥饿的适应性反应的一部分是外膜蛋白 OprH 的过度表达以及对聚阳离子抗生素多粘菌素 B 的抗性增加。在 oprH 基因下游鉴定了两个重叠的开放阅读框，其编码的蛋白质与鼠伤寒沙门氏菌的 PhoP-Phoa 双组分调节系统高度相似。铜绿假单胞菌PhoP无效突变体H851是通过phoP::xylE-Gm(R)转录融合构建的，并且显示OprH表达缺陷。相比之下，类似的 PhoQ 无效突变体 H854 (phoQ::xylE-GmR) 表现出 OprH 的组成型过表达。通过与携带 phoP 和 phoQ 基因的质粒互补，两种突变体都可以恢复正常的 Mg2+ 调节的 OprH 表达。对菌株 H851 和 H854 中 xylE 转录融合表达的儿茶酚-2,3-双加氧酶活性的测量表明，PhoP-PhoQ 参与 phoP-phoQ 以及 oprH 的调节。逆转录聚合酶链反应实验和 Northern 印迹分析揭示了 oprH、phoP 和 phoQ 连接成一个操纵子，该操纵子被证明处于 PhoP-PhoQ 和 oprH 的共同控制之下。 Mg2+离子浓度。此外，对两种突变株H851和H854的多粘菌素B抗性的研究表明，PhoP-PhoQ参与调节铜绿假单胞菌对外部Mg2+浓度的响应的多粘菌素抗性。
Rapid adaptation to environmental challenge is essential for the survival of many bacterial species, end is often effectively mediated by two-component regulatory systems. Part of the adaptive response of Pseudomonas aeruginosa to Mg2+ starvation is overexpression of the outer-membrane protein OprH and increased resistance to the polycationic antibiotic polymyxin B. Two overlapping open reading frames that encoded proteins with high similarities to the PhoP-Phoa two-component regulatory system of Salmonella typhimurium were identified downstream of the oprH gene. A P. aeruginosa PhoP-null mutant, H851, was constructed by means of a phoP::xylE-Gm(R) transcriptional fusion, and shown to be deficient in OprH expression. In contrast, an analogous PhoQ-null mutant, H854 (phoQ::xylE-GmR), exhibited constitutive overexpression of OprH. Normal Mg2+-regulated OprH expression could be restored in both mutants by complementation with a plasmid carrying the phoP and phoQ genes. Measurement of the catechol-2,3-dioxygenase activity, expressed from the xylE transcriptional fusion in strains H851 and H854, indicated that PhoP-PhoQ is involved in the regulation of phoP-phoQ as well as oprH, Reverse transcription polymerase chain reaction experiments and Northern blot analysis revealed linkage of oprH, phoP and phoQ into an operon that was demonstrated to be under the joint control of PhoP-PhoQ and Mg2+ ion concentration. In addition, studies of the polymyxin B resistance of the two mutant strains, H851 and H854, indicated that PhoP-PhoQ is involved in regulating P, aeruginosa polymyxin resistance in response to external Mg2+ concentrations.