Fmt Bypass in Pseudomonas aeruginosa Causes Induction of MexXY Efflux Pump Expression
Fmt Bypass in Pseudomonas aeruginosa Causes Induction of MexXY Efflux Pump Expression
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DOI：
10.1128/aac.00253-09
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发表时间：
2009-12-01
影响因子：
4.9
通讯作者：
Dean, Charles R.
中科院分区：
文献类型：
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作者：
Caughlan, Ruth E.;Sriram, Shubha;Dean, Charles R.
P. aeruginosa PAO1对肽去甲酰基酶抑制剂（PDF-I） LBM415的内在抗性是由MexAB-OprM和MexXY-OprM外排泵介导的，后者是由LBM415强烈诱导的。对于表达mexd - oprj外排泵的nfxB突变体，选择将mexAB-oprM缺失的PAO1（因此缺乏mexAB-oprM和MexXY-OprM功能）单步暴露于pdf -，表明这些化合物也是该泵的底物。通过使用高于外排所能容纳的LBM415水平来选择抗性突变体，产生了两组额外的突变，分别是甲硫基trna （fmet）甲酰转移酶（fmt）和folD基因。已知这两种机制都施加了体外生长缺陷（这里也观察到），可能是由于蛋白质合成的损害。我们推测这种蛋白质合成的固有损伤会以类似于LBM415或核糖体抑制化合物上调的方式上调mexXY的表达。转录谱分析和/或mexX::lux启动子融合分析显示，fmt和folD突变体强烈上调mexXY和另一个已知上调泵所需的基因PA5471。在trans中，fmt突变的互补逆转了这一组成表达。这支持了MexXY在核糖体功能或蛋白质合成受损时具有自然生理功能，fmt突变（fmt旁路）和folD突变产生细胞内MexXY诱导信号的观点。
The intrinsic resistance of P. aeruginosa PAO1 to the peptide deformylase inhibitor (PDF-I) LBM415 was mediated by the MexAB-OprM and MexXY-OprM efflux pumps, the latter of which was strongly induced by LBM415. Single-step exposure of PAO1 deleted for mexAB-oprM (therefore lacking both MexAB-OprM and MexXY-OprM functions) to PDF-Is selected for nfxB mutants, which express the MexCD-OprJ efflux pump, indicating that these compounds are also substrates for this pump. Selection of resistant mutants by use of levels of LBM415 greater than that accommodated by efflux yielded two additional groups of mutations, in the methionyl-tRNA(fmet) formyltransferase (fmt) and folD genes. Both mechanisms are known to impose an in vitro growth deficit (also observed here), presumably due to impairment of protein synthesis. We surmised that this inherent impairment of protein synthesis would upregulate expression of mexXY in a fashion similar to upregulation by LBM415 or by ribosome inhibitory compounds. Transcriptional profiling and/or mexX::lux promoter fusion analysis revealed that fmt and folD mutants were strongly upregulated for mexXY and another gene known to be required for upregulation of the pump, PA5471. Complementation of the fmt mutation in trans reversed this constitutive expression. This supports the notion that MexXY has a natural physiological function responding to impairment of ribosome function or protein synthesis and that fmt mutation (Fmt bypass) and folD mutation generate the intracellular mexXY-inducing signal.