Evolution of a new bacterial pathway for 4-nitrotoluene degradation.
Evolution of a new bacterial pathway for 4-nitrotoluene degradation.
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DOI：
10.1111/j.1365-2958.2011.07817.x
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发表时间：
2011-10
影响因子：
3.6
通讯作者：
Parales, Rebecca E.
中科院分区：
文献类型：
--
作者：
Ju, Kou-San;Parales, Rebecca E.
同化合成硝基芳烃化合物的细菌代表了独特的进化模型，因为它们的代谢途径处于适应和优化这些有毒化学物质的消耗的过程中。我们使用Acidovorax sp.菌株JS 42，这是能够生长在硝基苯和2-硝基甲苯，在实验中，以研究如何硝基芳烃降解途径的演变时，其宿主菌株的挑战与直接选择性压力同化非天然底物。虽然启动硝基苯和2-硝基甲苯降解的相同酶也将4-硝基甲苯氧化为4-甲基儿茶酚，这是JS 42的生长底物，但该菌株不能在4-硝基甲苯上生长。通过长期的实验室进化实验，我们获得了JS 42突变株，该突变株通过新的降解途径获得了对4-硝基甲苯的生长能力。这种新活性的潜在基础是由于编码双加氧酶的基因中特定突变的积累，该双加氧酶催化硝基芳烃底物的初始氧化，但在活性位点的远端位置，并且以前未知影响这种或相关酶的活性。我们构建了额外的突变双加氧酶，以确定导致改进酶的突变顺序。生化分析揭示了一个明确的，逐步改善双加氧酶的演变途径。
Bacteria that assimilate synthetic nitroarene compounds represent unique evolutionary models, as their metabolic pathways are in the process of adaptation and optimization for the consumption of these toxic chemicals. We used Acidovorax sp. strain JS42, which is capable of growth on nitrobenzene and 2-nitrotoluene, in experiments to examine how a nitroarene degradation pathway evolves when its host strain is challenged with direct selective pressure to assimilate non-native substrates. Although the same enzyme that initiates the degradation of nitrobenzene and 2-nitrotoluene also oxidizes 4-nitrotoluene to 4-methylcatechol, which is a growth substrate for JS42, the strain is incapable of growth on 4-nitrotoluene. Using long-term laboratory evolution experiments, we obtained JS42 mutants that gained the ability grow on 4-nitrotoluene via a new degradation pathway. The underlying basis for this new activity resulted from the accumulation of specific mutations in the gene encoding the dioxygenase that catalyzes the initial oxidation of nitroarene substrates, but at positions distal to the active site and previously unknown to affect activity in this or related enzymes. We constructed additional mutant dioxygenases to identify the order of mutations that led to the improved enzymes. Biochemical analyses revealed a defined, step-wise pathway for the evolution of the improved dioxygenases.
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影响因子：
4.4
作者：
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