A strain of Mycobacterium flavescens was isolated from polluted sediments. It was capable of utilizing pyrene as a sole source of carbon and energy. When pyrene was supplied as a suspension at 50 micrograms/ml, the generation time was 9.6 h and the rate of pyrene utilization was 0.56 microgram ml-1 day-1. In addition to pyrene, the strain could mineralize phenanthrene (17.7%) and fluoranthene (17.9%), but failed to mineralize naphthalene, chrysene, anthracene, fluorene, acenaphthene and benzo[a]pyrene, as determined by recovery of radiolabeled CO2 in incubations conducted for 2 weeks under growth conditions. Metabolites produced during growth on pyrene were detected and characterized by HPLC and GC-MS. The product of initial ring oxidation, 4,5-dihydroxy-4,5-dihydropyrene was identified, as well as ring-fission products including 4-phenanthroic acid, phthalic acid, and 4,5-phenanthrenedioic acid.

The ability of sediment bacteria to utilize polycyclic aromatic hydrocarbons (PAHs) when present as components of mixtures was investigated. One strain, identified as Mycobacterium flavescens, could utilize fluoranthene in the presence of pyrene, although utilization of pyrene was slower in the presence of fluoranthene than in its absence. The second strain, a Rhodococcus species, could utilize fluoranthene in the presence of anthracene, although the presence of fluoranthene slowed the rate of utilization of anthracene. Cometabolism of fluoranthene in these strains was confirmed by the isolation of metabolites of fluoranthene and by kinetic analysis of the rate of utilization of the growth substrate in the presence of fluoranthene. In both strains, metabolism of fluoranthene occurred on the fused ring of the fluoranthene molecule, producing 9-fluorenone-1-carboxylic acid. In the Rhodococcus sp., a second metabolite, a-(carboxymethylene)fluorene-1-carboxylic acid, was identified, indicating that this strain has the capacity to metabolize fluoranthene via ortho as well as meta cleavage. The presence of PAHs in a mixture produces interactive effects which can either increase or decrease the rate of utilization of individual PAHs, results which need to be taken into account when estimating rates of degradation in contaminated environments.

The ability of sediment bacteria to utilize polycyclic aromatic hydrocarbons (PAHs) when present as components of mixtures was investigated. One strain, identified as Mycobacterium flavescens, could utilize fluoranthene in the presence of pyrene, although utilization of pyrene was slower in the presence of fluoranthene than in its absence. The second strain, a Rhodococcus species, could utilize fluoranthene in the presence of anthracene, although the presence of fluoranthene slowed the rate of utilization of anthracene. Cometabolism of fluoranthene in these strains was confirmed by the isolation of metabolites of fluoranthene and by kinetic analysis of the rate of utilization of the growth substrate in the presence of fluoranthene. In both strains, metabolism of fluoranthene occurred on the fused ring of the fluoranthene molecule, producing 9-fluorenone-1-carboxylic acid. In the Rhodococcus sp., a second metabolite, a-(carboxymethylene)fluorene-1-carboxylic acid, was identified, indicating that this strain has the capacity to metabolize fluoranthene via ortho as well as meta cleavage. The presence of PAHs in a mixture produces interactive effects which can either increase or decrease the rate of utilization of individual PAHs, results which need to be taken into account when estimating rates of degradation in contaminated environments. ß

In order to delineate the roles of lignin and manganese peroxidases in the degradation of polycyclic aromatic hydrocarbons by Phanerochaete chrysosporium, the biodegradation of phenanthrene (chosen as a model for polycyclic aromatic hydrocarbons) was investigated. The disappearance of phenanthrene from the extracellular medium and mycelia was determined by using gas chromatography. The disappearance of phenanthrene from cultures of wild-type strains BKM-F1767 (ATCC 24725) and ME446 (ATCC 34541) under ligninolytic (low-nitrogen) as well as nonligninolytic (high-nitrogen) conditions was observed. The study was extended to two homokaryotic (basidiospore-derived) isolates of strain ME446. Both homokaryotic isolates, ME446-B19 (which produces lignin and manganese peroxidases only in low-nitrogen medium) and ME446-B5 (which totally lacks lignin and manganese peroxidase activities), caused the disappearance of phenanthrene when grown in lowas well as high-nitrogen media. Moreover, lignin and manganese peroxidase activities were not detected in any of the cultures incubated in the presence of phenanthrene. Additionally, the mineralization of phenanthrene was observed even under nonligninolytic conditions. The results collectively indicate that lignin

A Rhodococcus sp. isolated from contaminated river sediment was investigated to determine if the isolate could degrade high molecular mass polycyclic aromatic hydrocarbons. The Rhodococcus sp. was able to utilize anthracene (53%), phenanthrene (31%), pyrene (13%), and fluoranthene (5%) as sole source of carbon and energy, but not naphthalene or chrysene. In a study of the degradation of anthracene by a Rhodococcus sp., the identification of ring-fission products indicated at least two ring-cleavage pathways. One results in the production of 6,7-benzocoumarin, previously shown to be produced chemically from the product of meta cleavage of 1,2-dihydroxyanthracene, a pathway which has been well established in Gram-negative bacteria. The second is an ortho cleavage of 1,2-dihydroxyanthracene that produces 3-(2-carboxyvinyl)naphthalene-2-carboxylic acid, a dicarboxylic acid ring-fission product. This represents a novel metabolic pathway only identified in Gram-positive bacteria.