Project 5: Beyond Parent Compound Disappearance In The Bioremediation Of Polycycl

生物修复是去除污染土壤中多环芳烃的一种成熟技术，但先前的研究表明，它并不总是导致毒性的降低。毒性的原因以及避免或减少毒性的机制还没有被很好地理解。我们推测，多环芳烃降解菌产生的代谢产物，已被观察到积累在受田间污染的土壤和沉积物中，至少部分应对可能导致的毒性负责。 生物修复。我们还假设，生物修复条件会影响污染土壤中降解多环芳烃的微生物群落，进而影响多环芳烃的去除和代谢物的积累程度。以悬浮相生物反应器为实验平台，探讨生物修复条件对多环芳烃的去除和土壤毒性的影响。在我们将评估的条件中，有一种是在低剂量下添加疏水表面活性剂，我们 最近证明，经过常规生物修复后，可以改善残留在田间污染土壤中的多环芳烃的生物利用度和生物降解性。这一方法将通过在半连续过程中展示其有效性而得到进一步发展。我们将结合我们最近在稳定同位素探测方面的工作和高通量DNA测序方法来识别最可能影响处理土壤中多环芳烃的去除、代谢物积累和毒性的多环芳烃降解菌。它们的基因组 将对生物体进行测序，以确定与多环芳烃代谢相关的基因，并表达关键基因。代谢不同多环芳烃的能力的差异将与这些基因的序列差异相关，从而可以识别代谢物积累的遗传决定因素。同时，我们将使用分级技术和先进的分析工具来识别对处理后的土壤的毒性负责的化合物。最后，将评估在生物修复过程中可以控制的变量是否具有排除或减轻毒性的能力。我们的总体目标是填补关键的知识空白，这些知识将提供信息并改进生物修复的现场应用，从而真正降低风险。

Bioremediation is an established technology for removing PAHs from contaminated soil, but previous studies have shown that it does not always lead to a reduction in toxicity. The causes of toxicity and the mechanisms by which toxicity might be avoided or diminished are not well-understood. We hypothesize that metabolites produced by PAH-degrading bacteria, which have been observed to accumulate in field-contaminated soil and sediment, are responsible at least in part for the toxicity that can result from bioremediation. We also hypothesize that bioremediation conditions influence the community of PAH-degrading microorganisms in contaminated soil, which in turn influences both PAH removal and the extent to which metabolites might accumulate. We propose to explore the effects of bioremediation conditions on PAH removal and soil toxicity, using a slurry-phase bioreactor as the experimental platform. Among the conditions we will evaluate is the addition of a hydrophobic surfactant at a low dose, which we recently demonstrated can improve the bioavailability and biodegradation of PAHs that remained in a field-contaminated soil after conventional bioremediation. This approach will be developed further by demonstrating its efficacy in a semi-continuous process. We will combine our recent work on stable-isotope probing with a high-throughput DNA sequencing method to identify the PAH-degrading bacteria most likely to influence PAH removal, metabolite accumulation, and toxicity in the treated soil. Genomes of these organisms will be sequenced to identify genes associated with PAH metabolism, and the key genes will be expressed. Differences in the ability to metabolize various PAHs will be correlated to sequence differences in these genes so that genetic determinants of metabolite accumulation can be identified. In parallel, we will use fractionation techniques and advanced analytical tools to identify compounds responsible for toxicity of the treated soil. Finally, variables that can be controlled during bioremediation will be evaluated for their ability to preclude or mitigate toxicity. Our overall goal is to fill key gaps in knowledge that will inform and improve field applications of bioremediation that lead to true reductions in risk.