METABOLISM OF POLYHALOGENATED COMPOUNDS BY A GENETICALLY-ENGINEERED BACTERIUM

THE decomposition of organic compounds by bacteria has been studied fo r almost a century1, during which time selective enrichment culture ha s 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 com pounds are most frequently metabolized by anaerobic bacteria as a resu lt of reductive dehalogenation reactions5, the products of which are t ypically 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 whic h as a result metabolizes polyhalogenated compounds by means of sequen tial reductive and oxidative reactions to yield non-toxic products. Cy tochrome P450(cam) monooxygenase reduces polyhalogenated compounds8, w hich are bound at the camphor-binding site9,10, under subatmospheric o xygen tensions9. We find that these reduction products are oxidizable substrates for toluene dioxygenase. Perhalogenated chlorofluorocarbons also act as substrates for the genetically engineered strain.