The insecticide r-BHC (gamma isomer of 1, 2, 3, 4, 5, 6-hexachlorocyclohexane) was metabolized by 71 of 354 microorganisms (bacteria, and fungi) isolated from the environment. One of these isolates, a strain of Pseudomonas putida, was selected for nutrient and metabolic studies.Two metabolic patterns for the metabolism of r-BHC were detected in this organism, depending on the nutritional properties of the medium. The most common is a dehydrochlorination pathway where r-PCCH (l, 3, 4, 5, 6-pentachlorocyclohex-l-ene)is formed as one of the major products. The second pathway is a more complex NAD dependent pathway involving the production of large amounts of r-BTC (3, 4, 5, 6-tetrachlorocyclohex-l-ene).a-BHC is formed as a by-product of this second metabolic activity. Further degradation of r-BTC appears to proceed via an FAD dependent reductive dechlorination mechanism.In P. putida the ring opening process takes place on aromatic rings with only a few chlorines such as benzene, monochloro-or at most dichlorobenzenes via an oxidative route to yield CO2. Thus a combination of these three different metabolic systems is required to complete the degradation of 1-BHC in P. putida for the second pathway.
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