Global and cognate regulators control the expression of the organic solvent efflux pumps TtgABC and TtgDEF of Pseudomonas putida
Global and cognate regulators control the expression of the organic solvent efflux pumps TtgABC and TtgDEF of Pseudomonas putida
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DOI：
10.1046/j.1365-2958.2001.02310.x
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发表时间：
2001-02-01
影响因子：
3.6
通讯作者：
Ramos, JL
中科院分区：
文献类型：
--
作者：
Duque, E;Segura, A;Ramos, JL
恶臭假单胞菌DOT-T1 E在水-甲苯双液相上生长。该微生物的甲苯耐受性主要通过至少两个属于RND家族的外排泵来实现。TtgDEF外排泵由甲苯诱导，而另一个外排泵，称为TtgABC，在未暴露于甲苯的细胞中以高水平表达，在与甲苯一起生长的细胞中以较低水平表达。ttgR基因与ttgABC操纵子相邻，并从ttgA转录。在甲苯存在下生长的细胞中ttgR的表达水平比在甲苯不存在下高四倍。在TtgR缺陷的背景下，来自ttgA启动子的表达增加约20倍，表明TtgR抑制来自ttgA启动子的表达。在该突变体中，ttgR基因的背景表达也远高于野生型背景;然而，其表达水平在甲苯存在下增加。在ttgR突变体背景中，来自ttgD启动子的表达遵循与野生型中相同的表达模式。对恶臭假单胞菌pTn 5cat突变体的分析显示，该突变体对突然的甲苯冲击表现出增加的敏感性，而不管其先前是否暴露于低甲苯浓度，pTn 5cat已经中断了lrp样基因。ttgR基因在该突变体中以非常高的水平表达，伴随着ttgABC操纵子表达的抑制。第二ttgDEF外排泵在该突变株中以低水平表达，表明Lrp样蛋白是参与该菌株的溶剂耐受反应的全局调节蛋白。
Pseudomonas putida DOT-T1E grows on a water-toluene double liquid phase. Toluene tolerance in this microorganism is mainly achieved by at least two efflux pumps that belong to the RND family. The TtgDEF efflux pump is induced by toluene, whereas the other efflux pump, called TtgABC, is expressed at a high level in cells not exposed to toluene and at a lower level in cells grown with toluene. The ttgR gene is adjacent to the ttgABC operon and is transcribed divergently from ttgA. The expression level of ttgR was fourfold higher in cells growing in the presence of toluene than in its absence. In a TtgR-deficient background, expression from the ttgA promoter increased about 20-fold, suggesting that TtgR represses expression from the ttgA promoter. In this mutant, background expression of the ttgR gene was also much higher than in the wild-type background; however, its level of expression increased in the presence of toluene. In a ttgR mutant background, expression from the ttgD promoter followed the same pattern of expression as in the wild type. Analysis of a P. putida pTn5cat mutant that exhibited increased sensitivity to a sudden toluene shock, regardless of whether or not it was previously exposed to low toluene concentrations, revealed that pTn5cat had interrupted an lrp-like gene. The ttgR gene was expressed at very high levels in this mutant, with concomitant repression of expression of the ttgABC operon. The second ttgDEF efflux pump was expressed at low levels in this mutant strain, suggesting that the Lrp-like protein is a global regulatory protein involved in the solvent-tolerant response of this strain.