METABOLISM OF POLYHALOGENATED COMPOUNDS BY A GENETICALLY-ENGINEERED BACTERIUM

THE decomposition of organic compounds by bacteria has been studied for almost a century1, during which time selective enrichment culture has generated microoganisms capable of metabolizing thousands of organic compounds. But attempts to obtain pure cultures of bacteria that can metabolize highly halogenated compounds2, a large and important class of pollutants 3,4, have been largely unsuccessful. Polyhalogenated compounds are most frequently metabolized by anaerobic bacteria as a result of reductive dehalogenation reactions5, the products of which are typically substrates for bacterial oxygenases6. Complete metabolism of polyhalogenated compounds therefore necessitates the sequential use of anaerobic and aerobic bacteria7. Here we combine seven genes encoding two multi-component oxygenases in a single strain of Pseudomonas which as a result metabolizes polyhalogenated compounds by means of sequential reductive and oxidative reactions to yield non-toxic products. Cytochrome P450(cam) monooxygenase reduces polyhalogenated compounds8, which are bound at the camphor-binding site9,10, under subatmospheric oxygen tensions9. We find that these reduction products are oxidizable substrates for toluene dioxygenase. Perhalogenated chlorofluorocarbons also act as substrates for the genetically engineered strain.