The latter compound is metabolized through the well-established meta pathway for catechol degradation. The genes for these enzymes form part of the tod operon which is responsible for the degradation of toluene by this organism. A combination of transposon mutagenesis of the PpF1 chromosome, was well as the analysis of cloned chromosomal fragments, was used to determine the physical order of the genes in the tod operon. Zylstra, G.J., and D.T. Gibson. Pub. in Genetic Engineering, Vol.
Aromatic hydrocarbons have a ubiquitous distribution in nature.
The majority of these compounds are formed through the pyrolysis of organic matter. Pyrolysis at high temperatures leads to the formation of unsubstituted polycyclic aromatic hydrocarbons. Pyrolysis at low temperatures, such as those at which crude petroleum is formed, leads to the formation of alkyl-substituted aromatic hydrocarbons. Many of these compounds are suspected carcinogens. Increased use of petrochemicals by modern society has increased the amount of aromatic hydrocarbons found in air and soil samples.