Conversion of polycyclic aromatic hydrocarbons by <Emphasis Type="Italic">Sphingomonas</Emphasis> sp. VKM B-2434

A versatile bacterial strain able to convert polycyclic aromatic hydrocarbons (PAHs) was isolated, and a conversion by the isolate of both individual substances and PAH mixtures was investigated. The strain belonged to the Sphingomonas genus as determined on the basis of 16S rRNA analysis and was designated as VKM B-2434. The strain used naphthalene, acenaphthene, phenanthrene, anthracene and fluoranthene as a sole source of carbon and energy, and cometabolically oxidized fluorene, pyrene, benz[a]anthracene, chrysene and benzo[a]pyrene. Acenaphthene and fluoranthene were degraded by the strain via naphthalene-1,8-dicarboxylic acid and 3-hydroxyphthalic acid. Conversion of most other PAHs was confined to the cleavage of only one aromatic ring. The major oxidation products of naphthalene, phenanthrene, anthracene, chrysene, and benzo[a]pyrene were identified as salicylic acid, 1-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, o-hydroxyphenanthroic acid and o-hydroxypyrenoic acid, respectively. Fluorene and pyrene were oxidized mainly to hydroxyfluorenone and dihydroxydihydropyrene, respectively. Oxidation of phenanthrene and anthracene to the corresponding hydroxynaphthoic acids occurred quantitatively. The strain converted phenanthrene, anthracene, fluoranthene and carbazole of coal-tar-pitch extract.     

Profiles of polycyclic aromatic hydrocarbon metabolites after treatment with various inducers of microsomal rat liver monoxygenases (author's transl)

The microsomal oxidation of 12 frequently occurring environmental polycyclic aromatic hydrocarbons after incubation with rat-liver microsomes has been studied and their metabolites characterized by means of gas-liquid chromatography/mass spectrometry. The method enables the detection and characterisation of phenols, diols, triols, and tetrols as trimethylsilyl ethers beside the original hydrocarbons. Moreover, the induction properties of some carcinogenic and non-carcinogenic hydrocarbons (benz[a]anthracene, pyrene, chrysene, benzo[a]-pyrene, benzo[e]pyrene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene) have been studied. Except pyrene and benzo[e]pyrene, all compounds investigated significant but different induction factors. The relevance of the induction for an estimation of the biological effect of environmental polycyclic aromatic hydrocarbons is discussed.     

Protein engineering of Bacillus megaterium CYP102.The oxidation of polycyclic aromatic hydrocarbons.

Cytochrome P450 (CYP) enzymes are involved in activating the carcinogenicity of polycyclic aromatic hydrocarbons (PAHs) in mammals, but they are also utilized by microorganisms for the degradation of these hazardous environmental contaminants. Wild-type CYP102 (P450(BM-3)) from Bacillus megaterium has low activity for the oxidation of the PAHs phenanthrene, fluoranthene and pyrene. The double hydrophobic substitution R47L/Y51F at the entrance of the substrate access channel increased the PAH oxidation activity by up to 40-fold. Combining these mutations with the active site mutations F87A and A264G lead to order of magnitude increases in activity. Both these mutations increased the NADPH turnover rate, but the A264G mutation increased the coupling efficiency while the F87A mutation had dominant effects in product selectivity. Fast NADPH oxidation rates were observed (2250 min-1 for the R47L/Y51F/F87A mutant with phenanthrene) but the coupling efficiencies were relatively low (< 13%), resulting in a highest substrate oxidation rate of 110 min-1 for fluoranthene oxidation by the R47L/Y51F/A264G mutant. Mutation of M354 and L437 inside the substrate access channel reduced PAH oxidation activity. The PAHs were oxidized to a mixture of phenols and quinones. Notably mutants containing the A264G mutation showed some similarity to mammalian CYP enzymes in that some 9,10-phenanthrenequinone, the K-region oxidation product from phenanthrene, was formed. The results suggest that CYP102 mutants could be useful models for PAH oxidation by mammalian CYP enzymes, and also potentially for the preparation of novel PAH bioremediation systems.     

Genome-to-function characterization of novel fungal P450 monooxygenases oxidizing polycyclic aromatic hydrocarbons (PAHs)

Fungi, particularly the white rot basidiomycetes, have an extraordinary capability to degrade and/or mineralize (to CO₂) the recalcitrant fused-ring high molecular weight (?4 aromatic-rings) polycyclic aromatic hydrocarbons (HMW PAHs). Despite over 30 years of research demonstrating involvement of P450 monooxygenation reactions in fungal metabolism of HMW PAHs, specific P450 monooxygenases responsible for oxidation of these compounds are not yet known. Here we report the first comprehensive identification and functional characterization of P450 monooxygenases capable of oxidizing different ring-size PAHs in the model white rot fungus Phanerochaete chrysosporium using a successful genome-to-function strategy. In a genome-wide P450 microarray screen, we identified six PAH-responsive P450 genes (Pc-pah1-Pc-pah6) inducible by PAHs of varying ring size, namely naphthalene, phenanthrene, pyrene, and benzo(a)pyrene (BaP). Using a co-expression strategy, cDNAs of the six Pc-Pah P450s were cloned and expressed in Pichia pastoris in conjunction with the homologous P450 oxidoreductase (Pc-POR). Each of the six recombinant P450 monooxygenases showed PAH-oxidizing activity albeit with varying substrate specificity towards PAHs (3-5 rings). All six P450s oxidized pyrene (4-ring) into two monohydroxylated products. Pc-Pah1 and Pc-Pah3 oxidized BaP (5-ring) to 3-hydroxyBaP whereas Pc-Pah4 and Pc-Pah6 oxidized phenanthrene (3-ring) to 3-, 4-, and 9-phenanthrol. These PAH-oxidizing P450s (493-547 aa) are structurally diverse and novel considering their low overall homology (12-23%) to mammalian counterparts. To our knowledge, this is the first report on specific fungal P450 monooxygenases with catalytic activity toward environmentally persistent and highly toxic HMW PAHs.     

Mutagenicity of polycyclic hydrocarbons. V. Induction of sister-chromatid exchanges in vivo.

The potency of polycyclic hydrocarbons to induce SCEs in vivo was analysed. The most potent SCE-inducing compound was benzo[a]pyrene. Benzanthracene, benzo[b]fluoranthene, benzo[e]pyrene, phenanthrene, chrysene and dibenzanthracene enhanced the SCE frequency to a smaller extent. The number of anthracene-induced SCEs per metaphase was not increased as compared with the controls.     

Regio- and stereospecificity of homogeneous 3 alpha-hydroxysteroid-dihydrodiol dehydrogenase for trans-dihydrodiol metabolites of polycyclic aromatic hydrocarbons

The homogeneous 3 alpha-hydroxysteroid dehydrogenase (EC 1.1.1.50) of rat liver cytosol is indistinguishable from dihydrodiol dehydrogenase (trans-1,2-dihydrobenzene-1,2-diol dehydrogenase EC 1.3.1.20), Penning, T. M., Mukharji, I., Barrows, S., and Talalay, P. (1984) Biochem. J. 222, 601-611). Examination of the substrate specificity of the purified dehydrogenase for trans-dihydrodiol metabolites of polycyclic aromatic hydrocarbons indicates that the enzyme will catalyze the NAD(P)-dependent oxidation of trans-dihydrodiols of benzene, naphthalene, phenanthrene, chrysene, 5-methylchrysene, and benzo[a]pyrene under physiological conditions. Comparison of the utilization ratios Vmax/Km indicates that benzenedihydrodiol and the trans-1,2- and trans-7,8-dihydrodiols of 5-methylchrysene were most efficiently oxidized by the purified dehydrogenase, followed by the trans-7,8-dihydrodiol of benzo[a]pyrene and the trans-1,2-dihydrodiols of phenanthrene, chrysene, and naphthalene. The purified enzyme appears to display rigid regio-selectivity, since it will readily oxidize non-K-region trans-dihydrodiols but will not oxidize the K-region trans-dihydrodiols of phenanthrene and benzo[a]pyrene. The stereochemical course of enzymatic dehydrogenation was investigated by circular dichroism spectrometry. For the trans-1,2-dihydrodiols of benzene, naphthalene, phenanthrene, chrysene, and 5-methylchrysene, the dehydrogenase preferentially oxidized the (+)-[S,S]-isomer. Apparent inversion of this stereochemical preference occurred with the trans-7,8-dihydrodiol of 5-methylchrysene, as the (-)-enantiomer was preferentially oxidized. No change in the sign of the Cotton Effect was observed following oxidation of the racemic trans-7,8-dihydrodiol of benzo[a]pyrene, suggesting that both stereoisomers of this compound were substrates. Large-scale incubation of the [3H]-(+/-)-trans-7,8-dihydrodiol of benzo[a]pyrene with the purified dehydrogenase resulted in greater than 90% utilization of this potent proximate carcinogen, suggesting that the enzyme utilizes both the (-)-[R,R] and the (+)-[S,S]-stereoisomers, which confirms the circular dichroism result. These data show that dihydrodiol dehydrogenase displays the appropriate regio- and stereospecificity to catalyze the oxidation of both the major and minor non-K-region trans-dihydrodiols that arise from the microsomal metabolism of benzo[a]pyrene in vivo.     

Degradation of straight-chain aliphatic and high-molecular-weight polycyclic aromatic hydrocarbons by a strain of Mycobacterium austroafricanum

AIMS: Our goal was to characterize a newly isolated strain of Mycobacterium austroafricanum, obtained from manufactured gas plant (MGP) site soil and designated GTI-23, with respect to its ability to degrade polycyclic aromatic hydrocarbons (PAHs). METHODS AND RESULTS: GTI-23 is capable of growth on phenanthrene, fluoranthene, or pyrene as a sole source of carbon and energy; it also extensively mineralizes the latter two in liquid culture and is capable of extensive degradation of fluorene and benzo[a]pyrene, although this does not lead in either of these cases to mineralization. Supplementation of benzo[a]pyrene-containing cultures with phenanthrene had no significant effect on benzo[a]pyrene degradation; however, this process was substantially inhibited by the addition of pyrene. Extensive and rapid mineralization of pyrene by GTI-23 was also observed in pyrene-amended soil. CONCLUSIONS: Strain GTI-23 shows considerable ability to mineralize a range of polycyclic aromatic hydrocarbons, both in liquid and soil environments. In this regard, GTI-23 differs markedly from the type strain of Myco. austroafricanum (ATCC 33464); the latter isolate displayed no (or very limited) mineralization of any tested PAH (phenanthrene, fluoranthene or pyrene). When grown in liquid culture, GTI-23 was also found to be capable of growing on and mineralizing two aliphatic hydrocarbons (dodecane and hexadecane). SIGNIFICANCE AND IMPACT OF THE STUDY: These findings indicate that this isolate of Myco. austroafricanum may be useful for bioremediation of soils contaminated with complex mixtures of aromatic and aliphatic hydrocarbons.     

Degradation of polycyclic aromatic hydrocarbons by the copper(II)-hydrogen peroxide system

A non-enzymic system containing CuSO₄ (10 mmol/L) and hydrogen peroxide (100 mmol/L) was used for the degradation of three polycyclic aromatic hydrocarbons: phenanthrene, fluoranthene, and pyrene (all at 10 mmol/L). The system degraded the compounds rapidly and efficiently. After 1 d at room temperature, more than 80 % of pyrene, phenan-threne, and fluoranthene disappeared. Several products are formed during the reaction including a black precipitate.     

A fungal P450 (CYP5136A3) capable of oxidizing polycyclic aromatic hydrocarbons and endocrine disrupting alkylphenols: role of Trp(129) and Leu(324)

The model white rot fungus Phanerochaete chrysosporium, which is known for its versatile pollutant-biodegradation ability, possesses an extraordinarily large repertoire of P450 monooxygenases in its genome. However, the majority of these P450s have hitherto unknown function. Our initial studies using a genome-wide gene induction strategy revealed multiple P450s responsive to individual classes of xenobiotics. Here we report functional characterization of a cytochrome P450 monooxygenase, CYP5136A3 that showed common responsiveness and catalytic versatility towards endocrine-disrupting alkylphenols (APs) and mutagenic/carcinogenic polycyclic aromatic hydrocarbons (PAHs). Using recombinant CYP5136A3, we demonstrated its oxidation activity towards APs with varying alkyl side-chain length (C3-C9), in addition to PAHs (3-4 ring size). AP oxidation involves hydroxylation at the terminal carbon of the alkyl side-chain (ω-oxidation). Structure-activity analysis based on a 3D model indicated a potential role of Trp(129) and Leu(324) in the oxidation mechanism of CYP5136A3. Replacing Trp(129) with Leu (W129L) and Phe (W129F) significantly diminished oxidation of both PAHs and APs. The W129L mutation caused greater reduction in phenanthrene oxidation (80%) as compared to W129F which caused greater reduction in pyrene oxidation (88%). Almost complete loss of oxidation of C3-C8 APs (83-90%) was observed for the W129L mutation as compared to W129F (28-41%). However, the two mutations showed a comparable loss (60-67%) in C9-AP oxidation. Replacement of Leu(324) with Gly (L324G) caused 42% and 54% decrease in oxidation activity towards phenanthrene and pyrene, respectively. This mutation also caused loss of activity towards C3-C8 APs (20-58%), and complete loss of activity toward nonylphenol (C9-AP). Collectively, the results suggest that Trp(129) and Leu(324) are critical in substrate recognition and/or regio-selective oxidation of PAHs and APs. To our knowledge, this is the first report on an AP-oxidizing P450 from fungi and on structure-activity relationship of a eukaryotic P450 for fused-ring PAHs (phenanthrene and pyrene) and AP substrates.     

Anaerobic degradation of polycyclic aromatic hydrocarbons and alkanes in petroleum-contaminated marine harbor sediments.

Although polycyclic aromatic hydrocarbons (PAHs) have usually been found to persist under strict anaerobic conditions, in a previous study an unusual site was found in San Diego Bay in which two PAHs, naphthalene and phenanthrene, were oxidized to carbon dioxide under sulfate-reducing conditions. Further investigations with these sediments revealed that methylnaphthalene, fluorene, and fluoranthene were also anaerobically oxidized to carbon dioxide in these sediments, while pyrene and benzo[a]pyrene were not. Studies with naphthalene indicated that PAH oxidation was sulfate dependent. Incubating the sediments with additional naphthalene for 1 month resulted in a significant increase in the oxidation of [14C]naphthalene. In sediments from a less heavily contaminated site in San diego Bay where PAHs were not readily degraded, naphthalene degradation could be stimulated through inoculation with active PAH-degrading sediments from the most heavily contaminated site. Sediments from the less heavily contaminated site that had been adapted for rapid anaerobic degradation of high concentrations of benzene did not oxidize naphthalene, suggesting that the benzene- and naphthalene-degrading populations were different. When fuels containing complex mixtures of alkanes were added to sediments from the two sites, there was significant degradation in the alkanes. [14C]hexadecane was also anaerobically oxidized to 14CO2 in these sediments. Molybdate, a specific inhibitor of sulfate reduction, inhibited hexadecane oxidation. These results demonstrate that a wide variety of hydrocarbon contaminants can be degraded under sulfate-reducing conditions in hydrocarbon-contaminated sediments, and they suggest that it may be possible to use sulfate reduction rather than aerobic respiration as a treatment strategy for hydrocarbon-contaminated dredged sediments.     

Purification and characterization of an arene cis-dihydrodiol dehydrogenase endowed with broad substrate specificity toward polycyclic aromatic hydrocarbon dihydrodiols

Initial reactions involved in the bacterial degradation of polycyclic aromatic hydrocarbons (PAHs) include a ring-dihydroxylation catalyzed by a dioxygenase and a subsequent oxidation of the dihydrodiol products by a dehydrogenase. In this study, the dihydrodiol dehydrogenase from the PAH-degrading Sphingomonas strain CHY-1 has been characterized. The bphB gene encoding PAH dihydrodiol dehydrogenase (PDDH) was cloned and overexpressed as a His-tagged protein. The recombinant protein was purified as a homotetramer with an apparent Mr of 110,000. PDDH oxidized the cis-dihydrodiols derived from biphenyl and eight polycyclic hydrocarbons, including chrysene, benz[a]anthracene, and benzo[a]pyrene, to corresponding catechols. Remarkably, the enzyme oxidized pyrene 4,5-dihydrodiol, whereas pyrene is not metabolized by strain CHY-1. The PAH catechols produced by PDDH rapidly auto-oxidized in air but were regenerated upon reaction of the o-quinones formed with NADH. Kinetic analyses performed under anoxic conditions revealed that the enzyme efficiently utilized two- to four-ring dihydrodiols, with Km values in the range of 1.4 to 7.1 microM, and exhibited a much higher Michaelis constant for NAD+ (Km of 160 microM). At pH 7.0, the specificity constant ranged from (1.3 +/- 0.1) x 10(6) M(-1) s(-1) with benz[a]anthracene 1,2-dihydrodiol to (20.0 +/- 0.8) x 10(6) M(-1) s(-1) with naphthalene 1,2-dihydrodiol. The catalytic activity of the enzyme was 13-fold higher at pH 9.5. PDDH was subjected to inhibition by NADH and by 3,4-dihydroxyphenanthrene, and the inhibition patterns suggested that the mechanism of the reaction was ordered Bi Bi. The regulation of PDDH activity appears as a means to prevent the accumulation of PAH catechols in bacterial cells.     

PAH Degradation and Bioaugmentation by a Marine Methanotrophic Enrichment

Methanotrophic bacteria were enriched from marine sediments and screened for their ability to biotransform polycyclic aromatic hydrocarbons (PAHs). Characterization of the methanotrophic enrichment showed that it was dominated by a Type I methanotroph, although significant amounts of 18:1 fatty acids were detected, suggesting the presence of Type II methanotrophs in marine systems. The methanotrophic enrichment degraded phenanthrene, anthracene, and fluorene to below detectable levels in 15 days. Partial transformation of fluoranthene occurred over 15 days, but pyrene was not transformed. Radiolabeled phenanthrene was oxidized to carbon dioxide with significant production of polar intermediates. The oxidation was inhibited by acetylene, an inhibitor of methane monooxygenase. The addition of the methanotrophic enrichment to a marine culture grown on PAHs as the sole carbon sources increased the transformation rate of phenanthrene, anthracene, and fluorene. The highest removal rates were obtained with a mixture containing 90% methanotroph enrichment and 10% PAH-degrading enrichment (by biomass). Fluoranthene and pyrene degradation rates by the PAH-degrading enrichment were not significantly increased by the addition of the methanotrophic enrichment. A possible mechanism for the increased transformation rate was the rapid oxidation of PAHs by methane monooxygenase, forming an intermediate that is more bioavailable for utilization by the PAH-degraders.     

Novel metabolites in phenanthrene and pyrene transformation by Aspergillus niger.

Aspergillus niger, isolated from hydrocarbon-contaminated soil, was examined for its potential to degrade phenanthrene and pyrene. Two novel metabolites, 1-methoxyphenanthrene and 1-methoxypyrene, were identified by conventional chemical techniques. Minor metabolites identified were 1- and 2-phenanthrol and 1-pyrenol. No 14CO2 evolution was observed in either [14C]phenanthrene or [14C]pyrene cultures.     

Predicting the Efficacy of Polycyclic Aromatic Hydrocarbon Bioremediation in Creosote-Contaminated Soil Using Bioavailability Assays

Nonexhaustive extraction (propanol, butanol, hydroxypropyl-β-cyclodextrin [HPCD]), persulfate oxidation and biodegradability assays were employed to determine the bioavailability of polycyclic aromatic hydrocarbons (PAHs) in creosote-contaminated soil. After 16 weeks incubation, greater than 89% of three-ring compounds (acenaphthene, anthracene, fluorene, and phenanthrene) and 21% to 79% of four-ring compounds (benz[a]anthracene, chrysene, fluoranthene, and pyrene) were degraded by the indigenous microorganisms under biopile conditions. No significant decrease in five- (benzo[a]pyrene, benzo[b+k]fluoranthene) and six-ring compounds (benz[g,h,i]perylene, indeno[1,2,3-c,d]pyrene) was observed. Desorption of PAHs using propanol or butanol could not predict PAH biodegradability: low-molecular-weight PAH biodegradability was underestimated whereas high-molecular-weight PAH biodegradability was overestimated. Persulfate oxidation and HPCD extraction of creosote-contaminated soil was able to predict three- and four-ring PAH biodegradability; however, the biodegradability of five-ring PAHs was overestimated. These results demonstrate that persulfate oxidation and HPCD extraction are good predictors of PAH biodegradability for compounds with octanol-water partitioning coefficients of < 6.     

Mineralization of Polycyclic Aromatic Hydrocarbons by the White Rot Fungus Pleurotus ostreatus

The white rot fungus Pleurotus ostreatus was able to mineralize to (sup14)CO(inf2) 7.0% of [(sup14)C]catechol, 3.0% of [(sup14)C]phenanthrene, 0.4% of [(sup14)C]pyrene, and 0.19% of [(sup14)C]benzo[a]pyrene by day 11 of incubation. It also mineralized [(sup14)C]anthracene (0.6%) much more slowly (35 days) and [(sup14)C]fluorene (0.19%) within 15 days. P. ostreatus did not mineralize fluoranthene. The activities of the enzymes considered to be part of the ligninolytic system, laccase and manganese-inhibited peroxidase, were observed during fungal growth in the presence of the various polycyclic aromatic hydrocarbons. Although activity of both enzymes was observed, no distinct correlation to polycyclic aromatic hydrocarbon degradation was found.     

Purification and characterization of a benzo[a]pyrene hydroxylase from Pleurotus pulmonarius

Cytochrome P450 has been implicated in the process of biotransformation of polycyclic aromatic hydrocarbons and of other organic pollutants by white-rot fungi. We have purified and reconstituted a benzo[a]pyrene hydroxylating cytochrome P450 (P450) from microsomal fractions of the white rot fungus Pleurotus pulmonarius. The microsomal P450 was recovered using a combination of n-aminooctyl agarose and hydroxyapatite chromatography and had an apparent molecular mass of 55 kDa. The purified protein exhibited moderate affinity for benzo[a]pyrene with a K(s) of 66 microM calculated from the Type I substrate binding spectra produced. Reconstitution of activity was achieved and a turnover of 0.75 nmol 3-hydroxybenzo[a]pyrene product/min/nmol P450 was observed, comparable to levels of metabolism observed by animal cytochromes P450 involved in xenobiotic detoxification.     

Utilization of solubilized and crystalline mixtures of polycyclic aromatic hydrocarbons by a Mycobacterium sp.

A strain of Mycobacterium, that is able to degrade fluorene, phenanthrene, fluoranthene and pyrene was grown on various mixtures of these substrates. The polycyclic aromatic hydrocarbons (PAH) were provided either as crystals or solubilized by a surfactant. Mixed PAH were degraded simultaneously, but not in parallel, indicating that the degradation pathways were not incompatible. Certain interactions of the substrates were observed. For example, the degradation of solubilized pyrene was delayed in the presence of fluorene and enhanced in the presence of phenanthrene. Fluorene was degraded cometabolically with the other PAH serving as growth substrates, but not as the only source of carbon. The utilization of phenanthrene occurred at the fastest rate and was not affected by the presence of fluorene, pyrene or fluoranthene.     

Photomutagenicity of 16 polycyclic aromatic hydrocarbons from the US EPA priority pollutant list

The photomutagenicity of 16 polycyclic aromatic hydrocarbons (PAHs), all on the United States Environmental Protection Agency (US EPA) priority pollutant list, was studied. Concomitant exposing the Salmonella typhimurium bacteria strain TA102 to one of the PAHs and light (1.1 J/cm2 UVA+2.1 J/cm2 visible) without the activation enzyme S9, strong photomutagenic response is observed for anthracene, benz[a]anthracene, benzo[ghi]perylene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, and pyrene. Under the same conditions, acenaphthene, acenaphthylene, benzo[k]fluoranthene, chrysene, and fluorene are weakly photomutagenic. Benzo[b]fluoranthene, fluoranthene, naphthalene, phenanthrene, and dibenz[a,h]anthracene are not photomutagenic. These results indicate that PAHs can be activated by light and become mutagenic in Salmonella TA102 bacteria. At the same time, the mutagenicity for all the 16 PAHs was examined with the standard mutagenicity test with 10% S9 as the activation system. Benzo[b]fluoranthene, benzo[k]fluoranthene, chrysene, acenaphthylene, and fluorene are weakly mutagenic, while the rest of the PAHs are not. In general, the photomutagenicity of PAHs in TA102 does not correlate with their S9-activated mutagenicity in either TA102 or TA98/TA100 since they involve different activation mechanisms.     

Genotoxicity of polycyclic aromatic hydrocarbons in Escherichia coli PQ37.

In the present investigation, 32 polycyclic aromatic hydrocarbons (PAHs) were tested for genotoxicity in E. coli PQ37 using the standard tube assay of the SOS chromotest. PAHs such as benzo[ghi]fluoranthene, benzo[j]fluoranthene, benzo[a]pyrene, chrysene, dibenzo[a,l]pyrene, fluoranthene and triphenylene exhibited high genotoxicity when incubated in the presence of an exogenous metabolic activation mixture. The results were compared to those obtained with the Salmonella/microsome test.