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Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic compounds made up of two or more aromatic rings. In nature, these compounds pose problems because they are normally thermodynamically stable and not readily degraded. In addition, PAHs pose potential health risks to humans, as they can be toxic, mutagenic, and carcinogenic. Several microbial species contain genes that encode catabolic dioxygenases and monooxygenase enzymes, which are responsible for the initial step in the biodegradation of PAHs. In this study, polymerase chain reaction (PCR) was used as a molecular tool for the detection of these genes in environmental samples taken from the PAH-contaminated Chattanooga Creek in Chattanooga, TN. Nine primers sets, five designed for this study and four designed in study done by Baldwin et al. (2003), were used. These primers were based on the gene sequences of the large subunit of the dioxygenases or monooxygenases. We found the presence of one gene, nidA, found in the genome of several Mycobacterium sp., which encodes the large subunit of a dioxygenase capable of degrading high molecular weight (HMW) PAHs such as pyrene and benzo[a]pyrene.