Layton A C, Lajoie C A, Easter J P, Jernigan R, Beck M J, Sayler G S
University of Tennessee, Center for Environmental Biotechnology, Knoxville 37932-2567.
Ann N Y Acad Sci. 1994 May 2;721:407-22. doi: 10.1111/j.1749-6632.1994.tb47412.x.
Molecular diagnostic methods using DNA hybridization with specific gene probes are being developed for the monitoring of microbial populations capable of polychlorinated biphenyl (PCB) degradation in contaminated soils. Evaluation of composite samples from contaminated electrical substation soil by gas chromatography (GC) indicated that the PCBs present in the soil (approximately 200 ppm) resulted from contamination with Aroclor 1248. The PCBs have been weathered or degraded so that the lower molecular weight PCB congeners are no longer present. Microbiological and molecular site characterizations are in progress to determine the abundance of PCB degradative organisms and catabolic genes present. Cloned DNA fragments for the bphC gene (2,3-dihydroxybiphenyl dioxygenase) from the biphenyl/chlorobiphenyl degradative pathways of different organisms were used as gene probes to identify indigenous microorganisms with bphC gene sequences. In colony hybridization experiments, positive signals with the pDA251 gene probe were detected in cultures from both contaminated and uncontaminated soils. The degradative abilities of indigenous microorganisms and an added PCB-degradative bacterial strain were also monitored with [14C]4-chlorobiphenyl mineralization assays and gas chromatography of PCB residues extracted from the soils. Enrichment of the contaminated soil with biphenyl and chlorobiphenyls did not stimulate the indigenous microorganisms to degrade the soil PCB. Nevertheless, enrichment of the contaminated soil with biphenyl and chlorobiphenyl and addition of the PCB-degrading strain Alcaligenes eutrophus GG4202 did result in additional degradation of the soil PCB. The results obtained from these experiments should assist in developing and monitoring a remediation plan for these PCB-contaminated soils.
正在开发利用与特定基因探针进行DNA杂交的分子诊断方法，用于监测受污染土壤中能够降解多氯联苯（PCB）的微生物种群。通过气相色谱法（GC）对来自受污染变电站土壤的复合样品进行评估表明，土壤中存在的多氯联苯（约200 ppm）是由Aroclor 1248污染所致。这些多氯联苯已经风化或降解，因此较低分子量的多氯联苯同系物已不复存在。目前正在进行微生物学和分子层面的场地特征分析，以确定存在的多氯联苯降解生物和分解代谢基因的丰度。来自不同生物体的联苯/氯联苯降解途径的bphC基因（2,3 - 二羟基联苯双加氧酶）克隆DNA片段被用作基因探针，以鉴定具有bphC基因序列的本土微生物。在菌落杂交实验中，在来自受污染和未受污染土壤的培养物中均检测到了与pDA251基因探针的阳性信号。还通过[14C]4 - 氯联苯矿化测定法和从土壤中提取的多氯联苯残留物的气相色谱法，监测了本土微生物和添加的一种多氯联苯降解细菌菌株的降解能力。用联苯和氯联苯对受污染土壤进行富集，并未刺激本土微生物降解土壤中的多氯联苯。然而，用联苯和氯联苯对受污染土壤进行富集并添加多氯联苯降解菌株嗜碱产碱杆菌GG4202，确实导致了土壤中多氯联苯的进一步降解。这些实验获得的结果应有助于制定和监测针对这些受多氯联苯污染土壤的修复计划。
