Research Product

The oxidation of trichloroethylene (TCE) by bacteria possessing enzymes that act on toluene is now established for three species: P. cepacia, P. putida, and P. mendocina. In all cases an oxygenase acting directly on the aromatic ring of toluene is responsible for an attack on the alternate substrate TCE. P. cepacia, strain G4, was shown to catabolize toluene by a novel pathway. HPLC and GC/MC analysis indicated toluene hydroxylations at first the ortho and then meta positions to sequentially form o-cresol and 3-methylcatechol. Analysis of pathway intermediates (by GC/MS) formed in a defined atmosphere of 18O2 and 16O2 confirmed the sequential nature of this monooxygenation activity and the source of the oxygen as O2. The generation of several mutants unable to metabolize a variety of related aromatic compounds--toluene, phenol, cresol, catechol and hydroxymuconic semialdehyde (HMS)--revealed that the only mutants that also suffered loss of TCE-metabolizing ability were those that coincidentally lost the ability to hydroxylate toluene, phenol, o- or m-cresol. The principle of toluene ring oxygenation has led to the identification of strains of Nocardia, Alcaligenes, and Acinetobacter as capable of TCE degradation.