DEGRADATION OF PYRENE BY RHODOCOCCUS SP UW1

A Rhodococcus species, designated strain UW1, was isolated from contaminated soil using conventional enrichment and isolation techniques. The isolate was able to use pyrene as sole source of carbon and energy; it mineralized 72% of the pyrene within 2 weeks. During growth a metabolite was detected in the culture fluid and further characterized by UV- and mass spectrometry. There is evidence that this metabolite resulted from a recyclization of the direct meta-ring-fission product of pyrene after dihydroxylation in either the 1,2- or 4,5-position. At pH 7.0 and 30-degrees-C Rhodococcus sp. UW1 showed a maximum degradation rate of 0.08 mg pyrene/ml per day, while growing with a doubling time of 30 h. The activity of the initial dioxygenase system was characterized by measuring the oxygen-consumption rates of pyrene-induced resting cells, the maxima of which occurred at pH 7.2 and 45-degrees-C. Rhodococcus sp. UW1 could also use phenanthrene, anthracene, fluoranthene and chrysene as sole sources of carbon and energy, whereas naphthalene, dibenzofuran, fluorene and dibenzothiophene were only co-metabolized.