McLellan Sandra L, Warshawsky David, Shann Jodi R
Great Lakes WATER Institute, University of Wisconsin-Milwaukee, 53204, USA.
Environ Toxicol Chem. 2002 Feb;21(2):253-9.
Mycobacterium sp. strain RJGII-135 is capable of degrading a wide range of polycyclic aromatic hydrocarbons (PAHs), including benzo[a]pyrene (BaP). In this study, critical aspects of degradation were investigated, including compound uptake, relative rates of PAH degradation, and the effects of co-occurring PAH substrates on BaP degradation and mineralization to CO2. Mycobacterium sp. strain RJGII-135 was capable of degrading phenanthrene, anthracene, and pyrene at a 10- to 20-fold greater rate than benz[a]anthracene (BaA) and BaP. A significant amount of phenanthrene and pyrene, 30% and 10%, respectively, was completely mineralized, whereas less than 4% of anthracene, BaA, and BaP was mineralized. The PAH uptake assays demonstrated that high amounts of BaP and BaA, 81% and 75% of added compound, respectively, could be recovered from bacterial cell fractions after a 4-h incubation compared with pyrene (61%), anthracene (53%), and phenanthrene (47%). The half-saturation constant (Km) for pyrene was threefold lower for pyrene over BaP, suggesting that the degradation system in Mycobacterium sp. strain RJGII-135 has a higher affinity for pyrene, reaching maximal degradative activity at lower concentrations. No hybridization to dioxygenase gene probes nahAc, bphA1, or tolC1C2 was detected. Studies to investigate competition between different PAH substrates demonstrated that the rate of BaP metabolism was influenced by the presence of a second PAH substrate. The BaP metabolism was inhibited when coincubated with BaA, pyrene, and anthracene. Phenanthrene did not inhibit but enhanced BaP metabolism sixfold. These data suggest that induction effects of components of complex mixtures may be as important as competitive metabolism when assessing the ability of bacteria to effectively degrade high-molecular-weight PAHs in the environment.
分枝杆菌属菌株RJGII - 135能够降解多种多环芳烃（PAHs），包括苯并[a]芘（BaP）。在本研究中，对降解的关键方面进行了研究，包括化合物摄取、PAH降解的相对速率以及同时存在的PAH底物对BaP降解和矿化生成CO₂的影响。分枝杆菌属菌株RJGII - 135降解菲、蒽和芘的速率比苯并[a]蒽（BaA）和BaP快10至20倍。大量的菲和芘分别有30%和10%被完全矿化，而蒽、BaA和BaP的矿化率不到4%。PAH摄取试验表明，与芘（61%）、蒽（53%）和菲（47%）相比，在4小时孵育后，分别有81%和75%添加的化合物形式的大量BaP和BaA可从细菌细胞组分中回收。芘的半饱和常数（Km）比BaP低三倍，这表明分枝杆菌属菌株RJGII - 135中的降解系统对芘具有更高的亲和力，在较低浓度下达到最大降解活性。未检测到与双加氧酶基因探针nahAc、bphA1或tolC1C2的杂交。研究不同PAH底物之间竞争的实验表明，BaP代谢速率受第二种PAH底物存在的影响。与BaA、芘和蒽共同孵育时，BaP代谢受到抑制。菲没有抑制作用，反而使BaP代谢增强了六倍。这些数据表明，在评估细菌有效降解环境中高分子量PAHs的能力时，复杂混合物成分的诱导效应可能与竞争性代谢同样重要。
