Leahy J G, Byrne A M, Olsen R H
Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109-0620, USA.
Appl Environ Microbiol. 1996 Mar;62(3):825-33. doi: 10.1128/aem.62.3.825-833.1996.
The degradation of trichloroethylene (TCE) by toluene-oxidizing bacteria has been extensively studied, and yet the influence of environmental conditions and physiological characteristics of individual strains has received little attention. To consider these effects, the levels of TCE degradation by strains distinguishable on the basis of toluene and nitrate metabolism were compared under aerobic or hypoxic conditions in the presence and absence of nitrate and an exogenous electron donor, lactate. Under aerobic conditions with toluene-induced cells, strains expressing toluene dioxygenases (Pseudomonas putida F1, Pseudomonas sp. strain JS150, Pseudomonas fluorescens CFS215, and Pseudomonas sp. strain W31) degraded TCE at low rates, with less than 12% of the TCE removed in 18 h. In contrast, strains expressing toluene monooxygenases (Burkholderia cepacia G4, Burkholderia pickettii PKO1, and Pseudomonas mendocina KR1) degraded 36 to 67% of the TCE over the same period. Under hypoxic conditions (1.7 mg of dissolved oxygen per liter) or when lactate was added as an electron donor, the extent of TCE degradation by toluene-induced cells was generally lower. In the presence of lactate, degradation of TCE by denitrifying strain PKO1 was enhanced by nitrate under conditions in which dissimilatory nitrate reduction was observed. The results of experiments performed with strains F1, G4, PKO1, and KR1 suggested that TCE or an oxidation product induces toluene degradation and that TCE induces its own degradation in the monooxygenase strains. The role of TCE as an inducer of toluene oxygenase activity in PKO1 was confirmed by performing a promoter probe analysis, in which we found that TCE activates transcription from the PKO1 3-monooxygenase operon promoter.
甲苯氧化细菌对三氯乙烯（TCE）的降解已得到广泛研究，但环境条件和单个菌株生理特性的影响却很少受到关注。为了考虑这些影响，在有氧或缺氧条件下，比较了在存在和不存在硝酸盐及外源电子供体乳酸的情况下，基于甲苯和硝酸盐代谢可区分的菌株对TCE的降解水平。在有氧条件下，用甲苯诱导细胞时，表达甲苯双加氧酶的菌株（恶臭假单胞菌F1、假单胞菌属菌株JS150、荧光假单胞菌CFS215和假单胞菌属菌株W31）对TCE的降解速率较低，18小时内去除的TCE不到12%。相比之下，表达甲苯单加氧酶的菌株（洋葱伯克霍尔德菌G4、皮氏伯克霍尔德菌PKO1和门多西诺假单胞菌KR1）在同一时期降解了36%至67%的TCE。在缺氧条件下（每升溶解氧1.7毫克）或添加乳酸作为电子供体时，甲苯诱导细胞对TCE的降解程度通常较低。在存在乳酸的情况下，在观察到异化硝酸盐还原的条件下，反硝化菌株PKO1对TCE的降解会因硝酸盐而增强。用菌株F1、G4、PKO1和KR1进行的实验结果表明，TCE或其氧化产物会诱导甲苯降解，并且TCE在单加氧酶菌株中会诱导自身降解。通过进行启动子探针分析证实了TCE作为PKO1中甲苯加氧酶活性诱导剂的作用，我们发现TCE激活了PKO1 3-单加氧酶操纵子启动子的转录。
