ABSTRACT
Microorganisms, especially pseudomonads, can degrade a variety of recalcitrant synthetic chemical products and play a major role in bioconversion and bioremediation in natural environments. Some recalcitrant compounds, such as polychlorinated biphenyl and 7-hexachlorocyclohexane , have persisted long periods in environments and have caused serious pollution. A variety of degradative pathways for recalcitrant compounds have been intently studied. Many genes for degradation of recalcitrant compounds have been cloned, and their nucleotide sequences have been determined. The cloning of genes for degradation of recalcitrant compounds in a Pseudomonas host has some promise, as will be described in the next paragraph. However, the cloning system of E. coli usually has obvious advantages to clone and characterize genes. The cloning of degradative genes for recalcitrant compounds in a Pseudomonas host strain is more favorable than in an E. coli host, under several circumstances.
