Sarand I, Skärfstad E, Forsman M, Romantschuk M, Shingler V
Department of Cell and Molecular Biology, Umeå University, S-901 87 Umeå, Sweden.
Appl Environ Microbiol. 2001 Jan;67(1):162-71. doi: 10.1128/AEM.67.1.162-171.2001.
Pathway substrates and some structural analogues directly activate the regulatory protein DmpR to promote transcription of the dmp operon genes encoding the (methyl)phenol degradative pathway of Pseudomonas sp. strain CF600. While a wide range of phenols can activate DmpR, the location and nature of substituents on the basic phenolic ring can limit the level of activation and thus utilization of some compounds as assessed by growth on plates. Here we address the role of the aromatic effector response of DmpR in determining degradative properties in two soil matrices that provide different nutritional conditions. Using the wild-type system and an isogenic counterpart containing a DmpR mutant with enhanced ability to respond to para-substituted phenols, we demonstrate (i) that the enhanced in vitro biodegradative capacity of the regulator mutant strain is manifested in the two different soil types and (ii) that exposure of the wild-type strain to 4-methylphenol-contaminated soil led to rapid selection of a subpopulation exhibiting enhanced capacities to degrade the compound. Genetic and functional analyses of 10 of these derivatives demonstrated that all harbored a single mutation in the sensory domain of DmpR that mediated the phenotype in each case. These findings establish a dominating role for the aromatic effector response of DmpR in determining degradation properties. Moreover, the results indicate that the ability to rapidly adapt regulator properties to different profiles of polluting compounds may underlie the evolutionary success of DmpR-like regulators in controlling aromatic catabolic pathways.
途径底物和一些结构类似物可直接激活调节蛋白DmpR，以促进编码假单胞菌属CF600菌株（甲基）苯酚降解途径的dmp操纵子基因的转录。虽然多种酚类可激活DmpR，但基本酚环上取代基的位置和性质会限制激活水平，从而限制某些化合物在平板上生长评估中的利用情况。在此，我们探讨DmpR的芳香效应物反应在确定两种提供不同营养条件的土壤基质中的降解特性方面的作用。使用野生型系统和一个含有对对位取代酚反应能力增强的DmpR突变体的同基因对应物，我们证明：（i）调节突变体菌株增强的体外生物降解能力在两种不同土壤类型中均有体现；（ii）野生型菌株暴露于受4 - 甲基苯酚污染的土壤中会导致快速选择出一个表现出增强的化合物降解能力的亚群。对其中10个衍生物的遗传和功能分析表明，所有衍生物在DmpR的传感结构域中均存在一个介导每种情况下表型的单一突变。这些发现确立了DmpR的芳香效应物反应在确定降解特性方面的主导作用。此外，结果表明，调节蛋白特性快速适应不同污染化合物谱的能力可能是DmpR样调节蛋白在控制芳香族分解代谢途径方面进化成功的基础。
