Unexpected DNA damage caused by polycyclic aromatic hydrocarbons under standard laboratory conditions

The genotoxicity of 15 polycyclic aromatic hydrocarbons was determined with the alkaline version of the comet assay employing V79 lung fibroblasts of the Chinese hamster as target cells. These cells lack the enzymes necessary to convert PAHs to DNA-binding metabolites. Surprisingly, 11 PAHs, i.e., benzo[a]pyrene (BaP), benz[a]anthracene, 7,12-dimethylbenz[a]anthracene, 3-methylcholanthrene, fluoranthene, anthanthrene, 11H-benzo[b]fluorene, dibenz[a,h]anthracene, pyrene, benzo[ghi]perylene and benzo[e]pyrene caused DNA strand breaks even without external metabolic activation, while naphthalene, anthracene, phenanthrene and naphthacene were inactive. When the comet assay was performed in the dark or when yellow fluorescent lamps were used for illumination the DNA-damaging effect of the 11 PAHs disappeared. White fluorescent lamps exhibit emission maxima at 334.1, 365.0, 404.7, and 435.8 nm representing spectral lines of mercury. In the case of yellow fluorescent lamps these emissions were absent. Obviously, under standard laboratory illumination many PAHs are photo-activated, resulting in DNA-damaging species. This feature of PAHs should be taken into account when these compounds are employed for the initiation of skin cancer. The genotoxicity of BaP that is metabolically activated in V79 cells stably expressing human cytochrome P450-dependent monooxygenase (CYP1A1) as well as human epoxide hydrolase (V79-hCYP1A1-mEH) could not be detected with the comet assay performed under yellow light. Likewise the DNA-damaging effect of r-7,t-8-dihydroxy-t-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BaPDE) observed with the comet assay was only weak. However, upon inhibition of nucleotide excision repair (NER), which is responsible for the removal of stable DNA adducts caused by anti-BaPDE, the tail moment rose 3.4-fold in the case of BaP and 12.9-fold in the case of anti-BaPDE. These results indicate that the genotoxicity of BaP and probably of other compounds producing stable DNA adducts are reliably detected with the comet assay only when NER is inhibited.     

糙皮侧耳和鞘脂菌NS7对多环芳烃污染土壤的生物强化与协同作用

【背景】真菌和细菌被认为在多环芳烃污染土壤生物修复过程中发挥协同作用,目前在真实土壤体系中开展真菌-细菌协同降解研究较少。【目的】研究真菌和细菌对不同种类多环芳烃降解的差异及对蒽和苯并[a]蒽的生物强化与协同作用。【方法】选用多环芳烃降解真菌和细菌各一株,在液体纯培养体系下分析它们对不同种类多环芳烃降解的差异,在土壤体系中采用放射性同位素示踪技术研究2种微生物对蒽和苯并[a]蒽的生物强化与协同作用。【结果】供试细菌鞘脂菌NS7能够很好地降解低环种类多环芳烃,以蒽作为唯一碳源时可以将其完全降解,在复合污染条件下对菲、蒽、荧蒽、芘等降解效果突出(>90%),对苯并[a]芘降解效果较差(9.76%)。相比而言,供试真菌糙皮侧耳菌对苯并[a]芘具有更好的降解效果(21.18%),对低环多环芳烃降解效果明显不如降解菌NS7。在自然土壤中,蒽和苯并[a]蒽具有明显不同的矿化效率,分别为18.61%和4.28%,在蒽污染土壤中加入鞘脂菌NS7并未显著提高蒽的矿化率(P>0.05),相比而言,苯并[a]蒽污染土壤中加入糙皮侧耳显著提高了污染物矿化效率(2.24倍),表明真菌和细菌在土壤环境...     

Degradation of high molecular weight polycyclic aromatic hydrocarbons by Pseudomonas cepacia

Summary When inoculated at high cell densities, three strains of Pseudomonas cepacia degraded the polycyclic aromatic hydrocarbons (PAHs) benzo[a]pyrene, dibenz[a,h]anthracene and coronene as sole carbon and energy sources. After 63 days incubation, there was a 20 to 30% decrease in the concentration of benzo[a]pyrene and dibenz[a,h]anthracene and a 65 to 70% decrease in coronene concentration. The three strains were also able to degrade all the PAHs simultaneously in a PAH substrate mixture containing three-, four-, five- and seven-benzene ring compounds. Furthermore, improved degradation of the five- and seven-ring PAHs was observed when low molecular weight PAHs were present.     

Transformation and mineralization of benzo[<Emphasis Type="Italic">a</Emphasis>]pyrene by microbial cultures enriched on mixtures of three- and four-ring polycyclic aromatic hydrocarbons

Microorganisms originating from a soil contaminated by low levels of polycyclic aromatic hydrocarbons (PAHs) were enriched with three- and four-ring PAHs as primary substrates in the presence of benzo[a]pyrene (BaP). Most enrichment cultures, isolated in the presence or absence of a sorptive matrix, significantly transformed BaP. Evidence of BaP mineralization was obtained with cultures enriched on phenanthrene and anthracene. Our findings supplement literature data suggesting the wide occurrence of microbial activity against BaP. Journal of Industrial Microbiology & Biotechnology (2002) 28, 70–73 DOI: 10.1038/sj/jim/7000211 Received 11 December 2000/ Accepted in revised form 04 September 2001     

Metabolite repression inhibits degradation of benzo[a]pyrene and dibenz[a,h]anthracene by Stenotrophomonas maltophilia VUN 10,003

Large inocula of Stenotrophomonas maltophilia VUN 10,003 were used to investigate bacterial degradation of benzo[a]pyrene and dibenz[a,h]anthracene. Although strain VUN 10,003 was capable of degrading 10–15 mg l⁻¹ of the five-ring compounds in the presence of pyrene after 63 days, further addition of pyrene after degradation of the five-ring polycyclic aromatic hydrocarbons (PAHs) ceased did not stimulate significant decreases in the concentration of benzo[a]pyrene or dibenz[a,h]anthracene. However, pyrene was degraded to undetectable levels 21 days after its addition. The amount of benzo[a]pyrene and dibenz[a,h]anthracene degraded by strain VUN 10,003 was not affected by the initial concentration of the compounds when tested at 25–100 mg l⁻¹, by the accumulation of by-products from pyrene catabolism or a loss of ability by the cells to catabolise benzo[a]pyrene or dibenz[a,h]anthracene. Metabolite or by-product repression was suspected to be responsible for the inhibition: By-products from the degradation of the five-ring compounds inhibited their further degradation. Journal of Industrial Microbiology & Biotechnology (2002) 28, 88–96 DOI: 10.1038/sj/jim/7000216 Received 30 January 2001/ Accepted in revised form 10 October 2001     

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.     

Degradation of eight highly condensed polycyclic aromatic hydrocarbons by Pleurotus sp. Florida in solid wheat straw substrate

The degradation of eight unlabeled highly condensed polycyclic aromatic hydrocarbons (PAH) and the mineralization of three ¹⁴C-labeled PAH by the white-rot fungus Pleurotus sp. Florida was investigated. Three concentrations containing 50, 250 or 1250 μg each unlabeled PAH/5 g straw were added to sterile sea sand. Selected treatments were added subsequently with ¹⁴C-labeled pyrene, benzo[a]anthracene or benzo[a]pyrene. The PAH-loaded sea sand was then mixed into straw substrate and incubated. The disappearance of the unlabeled four-to six-ring PAH: pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a,h]anthracene and benzo[ghi]perylene, was determined by high-performance liquid chromatography. After 15 weeks of incubation, the recoveries were less than 25% for initial amounts of 50 μg (controls above 85%). The recoveries of unlabeled PAH increased in the inoculated samples with increasing concentrations applied. No correlation could be determined between the number of condensed rings of the PAH and the recoveries of added PAH. Pleurotus sp. Florida mineralized 53% [¹⁴C]pyrene, 25% [¹⁴C]benzo[a]anthracene and 39% [¹⁴C]benzo[a]pyrene to ¹⁴CO₂ in the presence of eight unlabeled PAH (50 μg applied) within 15 weeks. During the course of cultivation, Pleurotus sp. Florida degraded more than 40% of the wheat straw substrate. Variation of the initial concentration of PAH did not influence the extent of degradation of the organic matter. Received: 16 December 1996 / Received revision: 17 March 1997 / Accepted: 22 March 1997     

Effect of 10-aza-substitution on benzo[a]pyrene mutagenicity in vivo and in vitro

Benzo[a]pyrene (BaP), an environmental carcinogen, shows genotoxicity after metabolic transformation into the bay-region diol epoxide, BaP-7,8-diol 9,10-epoxide. 10-Azabenzo[a]pyrene (10-azaBaP), in which a ring nitrogen is located in the bay-region, is also a carcinogen and shows mutagenicity in the Ames test in the presence of the rat liver microsomal enzymes. In order to evaluate the effect of aza-substitution on in vivo genotoxicity, BaP and 10-azaBaP were assayed for their in vivo mutagenicity using the lacZ-transgenic mouse (Muta™Mouse). BaP was potently mutagenic in all of the organs examined (liver, lung, kidney, spleen, forestomach, stomach, colon, and bone marrow), as described in our previous report, whereas, 10-azaBaP was slightly mutagenic only in the liver and colon. The in vitro mutagenicities of BaP and 10-azaBaP were evaluated by the Ames test using liver homogenates prepared from several sources, i.e. CYP1A-inducer-treated rats, CYP1A-inducer-treated and non-treated mice, and humans. BaP showed greater mutagenicities than 10-azaBaP in the presence of a liver homogenate prepared from CYP1A-inducer-treated rodents. However, 10-azaBaP showed mutagenicities similar to or more potent than BaP in the presence of a liver homogenate or S9 from non-treated mice and humans. These results indicate that 10-aza-substitution markedly modifies the nature of mutagenicity of benzo[a]pyrene in both in vivo and in vitro mutagenesis assays.     

Peculiarities of interaction of monoclonal antibody B2 with polycyclic aromatic hydrocarbons and peptide-mimotope of benzo[<Emphasis Type="Italic">a</Emphasis>]pyrene

In order to determine the possible mechanisms of interactions of monoclonal antibody B2 with haptens and early synthesized peptide-mimotope of benzo[a]pyrene using the phage display method, amino acid sequences of variable fragments of heavy and light chains are determined and a model of Fab-fragment is constructed. The structure of the antibody active center is determined using molecular docking with polycyclic aromatic hydrocarbons. It is identified that the active center of monoclonal antibody B2 brings the two pockets of binding. The correlation between preliminarily obtained experimental data on the cross-reactivity of monoclonal antibody B2 with some ligands and calculated bond energy is found. It is shown that synthetic peptide-mimotope of benzo[a]pyrene is weak competing with the conjugate of benzo[a]pyrene for binding with monoclonal antibody B2. The immunization of mice with the conjugate of peptide and bovine serum albumin results in creation of antibodies to benz[a]anthracene and anthracene but not to benzo[a]pyrene. The model of peptide-mimotope of benzo[a]pyrene from pIII protein of bacteriophage is built. It is determined that tryptophan included into peptide composition can be exposed on the surface and be available for antibody. The data of modeling obtained in this study can be applicable for further optimization as both the structure of peptide-mimotope of benzo[a]pyrene and for active center of monoclonal antibody B2.     

A rapid and reproducible assay for collagenase using [1-14C]acetylated collagen.

A rapid, continuous, and highly sensitive fluorescence assay is described for the measurement of epoxide hydrase activity. The method is based on the large differences between the fluorescence spectra of certain K-region arene oxides and their corresponding trans-dihydrodiols. Enzymatic hydration of K-region arene oxides of phenanthrene, pyrene, benzo[a]pyrene, and 7,12-dimethylbenzo[a]anthracene was studied. The assay was most sensitive with benzo[a]pyrene-4,5-oxide as substrate. With 10 μm benzo[a]pyrene-4,5-oxide, enzymatic rates of 30 pmol of dihydrodiol/min/mg of protein are three to five times those of the blank without enzyme. The fluorometric method described has been used to study site-directed inhibitors of epoxide hydrase and the stereoselective hydration of racemic arene oxides.     

Potential Health Risk of Reused Creosote-Treated Old Railway Ties at Recreational Sites in Korea

Old creosote-treated railway ties reused at recreational sites in Korea are potential hazards, due to the presence of harmful substances in creosote, such as polycyclic aromatic hydrocarbons (PAHs). In such sites, PAHs in ties can be leached or emitted, and human exposure might then occur. In this study, the concentrations of 16 PAHs in soil, air, and tie surfaces in old creosote-treated railway ties reused in recreational sites were investigated, and the potential health risk of the ties was evaluated through two exposure scenarios: a recreational scenario (ingestion of and dermal contact with soil and inhalation of soil particles) and a playground scenario (ingestion after contact and dermal contact with ties). For the recreational scenario, the health risks of PAHs were safe; however, for the playground scenario, the carcinogenic risk of ingestion after contact, and dermal contact with benz(a)anthracene and benzo(a)pyrene on the tie surfaces, exceeded the acceptable risk level (10^–6). For the carcinogenic risks of ingestion after contact with ties, the probabilities of cancer development were 8 and 5 in one million people for benz(a)anthracene and benzo(a)pyrene, respectively. The carcinogenic risks for dermal contact with ties were 2.4 × 10^–6 and 1.4 × 10^–6 for benz(a)anthracene and benzo(a)pyrene, respectively.     

Fungal metabolism and detoxification of polycyclic aromatic hydrocarbons

The mutagenic activity of ethyl acetate extracts of culture medium from Cunninghamella elegans incubated 72 h with various polycyclic aromatic hydrocarbons (PAHs) was evaluated in the Salmonella typhimurium reversion assay. All of the PAH extracts were assayed in tester strains TA98 and TA100 both with and without metabolic activation using a liver fraction from Aroclor 1254-treated rats. None of the extracts from fungal incubations with the mutagenic PAHs, benzo[a]pyrene, 7,12-dimethylbenz[a]anthracene, 3-methylcholanthrene and benz[a]anthracene, as well as the non-mutagenic PAHs, naphthalene, phenanthrene and anthracene, displayed any appreciable mutagenic activity. In addition, time course experiments indicated that the rate of decrease in mutagenic activity in the extracts from cultures incubated with benzo[a]pyrene or 7,12-dimethylbenz[a]anthracene was coincident with the rate of increase in total metabolism. The results demonstrated the ability of the fungus C. elegans to detoxify known carcinogens and mutagens and suggests that this organism may play an important role in the metabolism and inactivation of PAHs in the environment.Abbreviations hplc high performance liquid chromatography - tlc thin layer chromatography - PAH polycyclic aromatic hydrocarbon     

An enzyme-linked immunosorbent assay for detection of pyrene and related polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) can form DNA-binding compounds that show genotoxicity and carcinogenicity. Pyrene, as a PAH, was covalently linked to carrier protein bovine serum albumin and ovalbumin. A monoclonal antibody (McAb) was produced that showed high cross-reactivity values with chrysene (169.73%), benzo[a]pyrene (693.34%), benzo[a]anthracene (16.36%), and indeno[1,2,3-cd]pyrene (40.96%) and showed no significant cross-reactivity values with other homologues (<0.1%). A competitive enzyme-linked immunosorbent assay (ELISA) was developed for detection of pyrene and some homologues in water samples. The detection limit of the assay was 65.08 pg ml⁻¹. The average recoveries of PAHs from tap water, lake water, and mineral water were 99.13, 99.74, and 99.19%, respectively, indicating that matrices of water samples do not interfere with the assay. The results demonstrated that the developed ELISA seems to be a potential method for monitoring of pyrene and some homologous PAHs in water samples.     

Degradation of Polycyclic Aromatic Hydrocarbons by Crude Extracts from Spent Mushroom Substrate and its Possible Mechanisms

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) by pure laccase has been reported, but the high cost limited its application in environmental bioremediation. Here, we reported a study about PAHs degradation by crude extracts (CEs) containing laccase, which were obtained by extracting four spent mushroom (Agaricus bisporus, Pleurotus eryngii, Pleurotus ostreatus, and Coprinus comatus) substrates. The results showed that anthracene, benzo[a]pyrene, and benzo[a]anthracene were top three degradable PAHs by CEs while naphthalene was most recalcitrant. The PAHs oxidation was enhanced in the presence of 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). Laccase included in CE might play a major role in PAHs degradation. The maximum degradation rate of anthracene and benzo[a]pyrene was observed by using crude extracts from P. eryngii while the highest laccase activities were found in crude extracts from A. bisporus, moreover, crude extracts from P. eryngii, which contained less laccase activities, degraded more anthracene and benzo[a]pyrene than pure laccase with higher laccase activities. The lack of correlation between laccase activity and PAHs degradation rate indicated that other factors might also influence the PAHs degradation. Boiled CEs were added to determine the effect on PAHs degradation by laccase. The results showed that all four boiled CEs had improved the PAHs oxidation. The maximum improvement was observed by adding CEs from P. eryngii. It suggested that some mediators indeed existed in CEs and CEs from P. eryngii contained most. As a result, CEs from P. eryngii has the most application potential in PAHs bioremediation.     

Two-step error-prone bypass of the (+)- and (−)-trans-anti-BPDE-N-dG adducts by human DNA polymerases η and κ

Benzo[a]pyrene is a polycyclic aromatic hydrocarbon (PAH) associated with potent carcinogenic activity. Mutagenesis induced by benzo[a]pyrene DNA adducts is believed to involve error-prone translesion synthesis opposite the lesion. However, the DNA polymerase involved in this process has not been clearly defined in eukaryotes. Here, we provide biochemical evidence suggesting a role for DNA polymerase η (Polη) in mutagenesis induced by benzo[a]pyrene DNA adducts in cells. Purified human Polη predominantly inserted an A opposite a template (+)- and (−)-trans-anti-BPDE-N²-dG, two important DNA adducts of benzo[a]pyrene. Both lesions also dramatically elevated G and T mis-insertion error rates of human Polη. Error-prone nucleotide insertion by human Polη was more efficient opposite the (+)-trans-anti-BPDE-N²-dG adduct than opposite the (−)-trans-anti-BPDE-N²-dG. However, translesion synthesis by human Polη largely stopped opposite the lesion and at one nucleotide downstream of the lesion (+1 extension). The limited extension synthesis of human Polη from opposite the lesion was strongly affected by the stereochemistry of the trans-anti-BPDE-N²-dG adducts, the nucleotide opposite the lesion, and the sequence context 5′ to the lesion. By combining the nucleotide insertion activity of human Polη and the extension synthesis activity of human Polκ, effective error-prone lesion bypass was achieved in vitro in response to the (+)- and (−)-trans-anti-BPDE-N²-dG DNA adducts.     

DNA damage (comet assay) and 8-oxodGuo (HPLC-EC) in relation to oxidative stress in the freshwater bivalve Unio tumidus

The relationships between DNA damage and oxidative stress in the digestive gland, gills and haemocytes of the freshwater bivalve Unio tumidus were investigated. Two markers of genotoxicity were measured: DNA breaks by means of the comet assay, and oxidative DNA lesions by means of 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo) measured using high-performance liquid chromatography (HPLC) coupled to electrochemical detection. Lipid peroxidation was evaluated by measuring malondialdehyde (MDA) tissue levels. Effects were studied after exposure of bivalves for 6 days to benzo[a]pyrene (B[a]P) (50 and 100 μg?l^?1) and ferric iron (20 and 40 mg?l^?1), applied alone or in combination. Lipid peroxidation in the digestive gland and gills resulted from exposure to Fe³⁺ or B[a]P whatever the concentrations tested. DNA oxidatively formed lesions were induced in the two tissues at a higher level after B[a]P exposure than after Fe³⁺ treatment. No significant dose–response relationship was found with the two compounds and no synergistic effect was observed between Fe³⁺ and B[a]P. The gills appeared less sensitive than the digestive gland to DNA lesions expressed as 8-oxodGuo and comet results. Good correlations were noted between 8-oxodGuo and comet. MDA and DNA damage did not correlate as well, although it was stronger in the digestive gland than in the gills. Production of mucus by the gills likely served to prevent lesions by reducing the bioavailability of the chemicals tested, which could explain that dose–effect relationships and synergistic effects were not observed.     

Induction of in vivo DNA adducts by 4 industrial by-products in the rat-lung-cell system

Benz[a]anthracene (BA), dibenz[a,h]anthracene (DBA), dibenzo[a,i]pyrene (DBP), and dibenz[a,h]acridine (DBAC) are by-products found in many industrial wastes and emissions. Workers in the related occupational settings are potentially exposed to these substances through inhalation. In the present study, induction of DNA adducts in vivo by these chemicals was investigated using ³²P-postlabeling analysis in the rat-lung-cell system. The potency of DNA-adduct inducing activity was also compared to that of two cytogenetic endpoints i.e., sister-chromatid exchange (SCE) and micronucleus formation. Via intratracheal instillation, male CD rats (6/group) were dosed 3 times with BA, DBA, DBP or DBAC in a 24-h interval. Lung cells were enzymatically separated and used to determine the frequency of DNA adducts, SCE and micronuclei. Results show that all 4 test compounds induced DNA adducts, SCEs, and micronuclei in the rat-lung cell in vivo and that the postlabeling DNA adduct assay detected genotoxic activity at lower dose levels than the two cytogenetic assays. These findings suggest that BA, DBA, DBP or DBAC are rat pulmonary genetoxicants and the DNA-adduct assay is more sensitive than SCE or micronucleus assays for detecting the pulmonary genotoxicity of these industrial PAHs in the in vivo rat-lung-cell system.     

Biodegradation of selected UV-irradiated and non-irradiated polycyclic aromatic hydrocarbons (PAHs)

Biodegradation of UV-irradiated anthracene, pyrene,benz[a]anthracene,and dibenz[a,h]anthracene was comparedto that of the non-irradiated samples, individuallyand in synthetic mixtures with enrichment cultures.Combined treatment was repeated for individual anthraceneand for the PAH mixture with Sphingomonas sp.strain EPA 505 and Sphingomonas yanoikuyae.Enrichment culture studies were performed on the PAHmixtures in the presence of the main photoproduct ofanthracene, pure 9,10-anthracenedione. Photochemicallypretreated creosote solutions were also subjected tobiodegradation and the results were compared tothose of the non-irradiated solutions. The primaryinterest was on 16 polycyclic aromatic hydrocarbons(PAHs) listed as priority pollutants by European Union(EU) and the United States Environmental ProtectionAgency (USEPA). Irradiation accelerated thebiodegradation onset for anthracene, pyrene, andbenz[a]anthracene when they were treatedindividually. The biodegradation of irradiatedpyrene started with no lag phase andwas complete by 122 h whereas biodegradation of thenon-irradiated sample had a lag of 280 h andresulted in complete degradation by 720 h. Biodegradation ofPAHs was accelerated in synthetic mixtures, especiallyin the presence of pure 9,10-anthracenedione.In general, irradiation had no effect on the biodegradation of PAHsincubated in synthetic mixtures or with pure cultures. Undercurrent experimental conditions, the UV-irradiation invariablyreduced the biodegradation of PAHs in creosote. Based onthe results of the present and previous photochemical-biologicalstudies of PAHs, the influence of the photochemical pretreatmenton the biodegradation is highly dependent on the compoundsbeing treated and other process parameters.     

Model reactions of the quinone metabolites of carcinogenic hydrocarbons with t-butylthiol

Reactions of benzo[a]pyrene 1,6-dione with t-butylthiolate affords two products of conjugate addition and subsequent spontaneous reoxidation, namely, 2-t-butylthio- and 2,4-di-t-butylthiobenzo[a]pyrene 1,6-dione. Analogous reaction of benzo[a]pyrene 3,6-dione furnished only 12-t-butylthiobenzo[a]pyrene 3,6-dione. Structural assignments are based on analysis of the high-resolution 270-MHz Fourier-transform proton nmr spectra. In both products the attachment of the entering nucleophile is on an aromatic ring remote from either of the carbonyl groups, the first examples of such detected. The biological significance of these results with relation to the potential reactions of these quinones, known to be major metabolites of the carcinogen benzo[a]pyrene, with glutathione, cysteine, and proteins in vivo is discussed.     

Screening of ectomycorrhizal fungi for degradation of polycyclic aromatic hydrocarbons

Ectomycorrhizal fungi belonging to 16 species (27 strains) were tested for their ability to degrade polycyclic aromatic hydrocarbons (PAHs): phenanthrene, chrysene, pyrene and benzo[a]pyrene. Cultivated on a complex liquid medium, most of the fungi tested were able to metabolise these compounds. Approximately 50% of the benzo[a]pyrene was removed by strains of Amanita excelsa, Leccinum versipelle, Suillus grevillei, S. luteus, and S. variegatus during a 4-week incubation period. The same amount of phenanthrene was also metabolised by A. muscaria, Paxillus involutus, and S. grevillei. The degradation of the other two PAHs was, for the most part, less effective. Only S. grevillei was able to remove 50% of the pyrene, whereas Boletus edulis and A. muscaria removed 35% of the chrysene. Received: 12 April 1999 / Received revision: 27 May 1999 / Accepted: 28 May 1999