Utilization of mixtures of polycyclic aromatic hydrocarbons by bacteria isolated from contaminated sediment

Abstract 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.