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 recta-ringfission product of pyrene after dihydroxylation in either the 1,2-or 4,5-position. At pH 7.0 and 30°C Rhodococcus sp. UWI 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°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.

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The degradation of fluoranthene by pure cultures ofAlcalioenes denitrificans WW1, isolated from contaminated soil samples, was investigated. The strain showed m a x i m u m degradation rates of 0.3 mg fluoranthene/ml per day. A. denitrificans was able to utilize also naphthalene, 1-and 2-methylnaphthalene, phenanthrene, and anthracene as sole carbon sources and to co-metabolize fluorene, pyrene, and benzo(a)anthracene. During growth on fluoranthene in batch culture two metabolic products that were completely degraded before growth entered the stationary phase were detected in the culture fluid. Analyses by UV, mass and N M R spectroscopy identified the products as acenaphthenone and 3-hydroxymethyl-4,5-benzocoumarine. Fluoranthene-grown resting cells of A. denitrificans showed degradative activity towards 2,3-dihydroxybenzoic acid, pyrogallol, salicylic acid, and catechol. The enzymatic activities in extracts of fluoranthene-induced cells indicate a meta ring fission involved in the degradation of fluoranthene. From these data new aspects of the biodegradative pathway of fluoranthene have been predicted.

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