INDIRECT IDENTIFICATION OF AN UNSTABLE INTERMEDIATE IN GAMMA-HCH DEGRADATION BY PSEUDOMONAS-PAUCIMOBILIS UT26

While a postulated intermediate, 1,3,4,5-tetrachlorocyclohexa-1,4-diene(1,4-TCDN), is one of the key-compounds in gamma-hexachlorocyclohexane(gamma-HCH) degradation by Pseudomonas paucimobilis UT26(UT26), it has neither been isolated nor identified yet. Thus, an indirect identification was attempted to demonstrate its existence by a chemical oxidation of the microbial degradation products in situ. 1,2,4,5-Tetrachlorobenzene(1,2,4,5-TeCB) was newly produced by the chemical oxidation with hydrogen peroxide under iron(II) of W medium containing degradation products in situ of gamma-1,3,4,5,6-pentachlorocyclohexene(gamma-PCCH) by Escherichia coli MV1184(E. coli) which possesses the dehydrochlorinating activity of UT26. The chemical oxidation required the preceding enzymatic reactions to gamma-PCCH by E. coli for the production of 1,2,4,5-TeCB. In facts, 1,2,4,5-TeCB was not produced from gamma-PCCH by either of the chemical or enzymatic reaction alone. Considering these results and the fact that hydrogen peroxide is known to dehydrogenate chemical compounds, it was concluded that 1,2,4,5-TeCB was produced directly from the unstable intermediate, 1,4-TCDN, on yielded from gamma-PCCH by an enzymatic dehydrochlorination.