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.     

Microbial degradation of high and low molecular weight polyaromatic hydrocarbons in a two-phase partitioning bioreactor by two strains of Sphingomonas sp.

A mixture of six polyaromatic hydrocarbons (naphthalene, phenanthrene, fluoranthene, pyrene, chyrysene and benzo[a]pyrene), varying in size from 2 to 5 rings, was dissolved in dodecane, and used as the delivery phase of a partitioning bioreactor. Two species of Sphingomonas were then used individually, and as a consortium, to determine which of the PAHs were degraded. Only low molecular weight PAHs (naphthalene, phenanthrene and fluoranthene) were degraded by the individual strains, but the consortium degraded all substrates either to completion or near completion.     

Aryl hydrocarbon receptor-mediated activity of mutagenic polycyclic aromatic hydrocarbons determined using in vitro reporter gene assay

Activation of aryl hydrocarbon receptor (AhR) by 30 polycyclic aromatic hydrocarbons (PAHs) was determined in the chemical-activated luciferase expression (CALUX) assay, using two exposure times (6 and 24h), in order to reflect the metabolization of PAHs. AhR-inducing potencies of PAHs were expressed as induction equivalency factors (IEFs) relative to benzo[a]pyrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In 24h exposure assay, the highest IEFs were found for benzo[k]fluoranthene, dibenzo[a,h]anthracene and dibenzo[a,k]fluoranthene (approximately three orders of magnitude lower than TCDD) followed by dibenzo[a,j]anthracene, benzo[j]fluoranthene, indeno[1,2,3-cd]pyrene, and naphtho[2,3-a]pyrene. The 6h exposure to PAHs led to a significantly higher AhR-mediated activity than the 24h exposure (generally by two orders of magnitude), probably due to the high rate of PAH metabolism. The strongest AhR inducers showed IEFs approaching that of TCDD. Several PAHs, including some strong mutagens, such as dibenzo[a,l]pyrene, cyclopenta[cd]pyrene, and benzo[a]perylene, elicited only partial agonist activity. Calculation of IEFs based on EC25 values and/or 6h exposure data is suggested as an alternative approach to estimation of toxic potencies of PAHs with high metabolic rates and/or the weak AhR agonists. The IEFs, together with the recently reported relative mutagenic potencies of PAHs [Mutat. Res. 371 (1996) 123; Mutat. Res. 446 (1999) 1] were combined with data on concentrations of PAHs in extracts of model environmental samples (river sediments) to calculate AhR-mediated induction equivalents and mutagenic equivalents. The highest AhR-mediated induction equivalents were found for benzo[k]fluoranthene and benzo[j]fluoranthene, followed by indeno[1,2,3-cd]pyrene, dibenzo[a,h]anthracene, benzo[a]pyrene, dibenzo[a,j]anthracene, chrysene, and benzo[b]fluoranthene. High mutagenic equivalents in the river sediments were found for benzo[a]pyrene, dibenzo[a,e]pyrene, and naphtho[2,3-a]pyrene and to a lesser extent also for benzo[a]anthracene, benzo[b]fluoranthene, indeno[1,2,3-cd]pyrene, benzo[j]fluoranthene, dibenzo[a,e]fluoranthene and dibenzo[a,i]pyrene. These data illustrate that AhR-mediated activity of PAHs, including the highly mutagenic compounds, occurring in the environment but not routinely monitored, could significantly contribute to their adverse effects.     

Pyrene Biodegradation by Bacillus spp. Isolated from Coal Tar–Contaminated Soil

Aerobic, mesophilic bacteria from coal tar–contaminated soil were analyzed for pyrene utilization capacity and identified by 16S ribosomal DNA sequencing as members of three genera: Bacillus spp., Pseudomonas sp., and Rhodococcus sp. The soil contained nine different hazardous polyaromatic hydrocarbons (PAHs): benzo[g, h, i]perylene, dibenzo[a, h]anthracene, indeno[1,2,3-c,d]pyrene, pyrene, acenaphthylene, fluorene, phenanthrene, benzo[k]fluoranthene, and benzo[b]fluoranthene. Bacillus spp. (PK-6) MTCC 1005 showed 56.4% utilization of pyrene (C₁₆H₁₀) (50 μg ml^?1) in 4 days, with growth associated biosurfactant activity and resulted in the formation of five new intermediates: phenanthrene (C₁₄H₁₀), 9,10-diphenylphenanthrene (C₂₆H₁₈), 9-methoxyphenanthrene (C₁₅H₁₂O), 5,6,7,8-tetrahydro-1-naphthoic acid (C₁₁H₁₂O₂), and 1,6,7-trimethylnaphthalene (C₁₃H₁₄). The results suggested that Bacillus spp. could be found suitable for practical field application for effective in situ PAH bioremediation.     

Levels,Sources, and Toxic Potential of Polycyclic Aromatic Hydrocarbons in Urban Soil of Delhi,India

This study was done to determine the concentration of PAHs in urban soil of Delhi (India). Surface top soil (up to 10 cm depth) samples were collected from four different sampling sites including industrial, roadside, residential, and agricultural areas of Delhi and 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) were evaluated. Total PAH concentrations at industrial, roadside, residential, and agricultural sites were 11.46 ± 8.39, 6.96 ± 4.82, 2.12 ± 1.12, and 1.55 ± 1.07 mg/kg (dry weight), respectively, with 3–7 times greater concentrations in industrial and roadside soils than that in residential and agricultural soils. The PAH pattern was dominated by 4- and 5-ring PAHs (contributing >50% to the total PAHs) at industrial and roadside sites with greater concentration of fluoranthene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]anthracene, benzo[ghi]perylene, and pyrene, whereas, residential and agricultural sites showed a predominance of low molecular weight 2- and 3-ring PAHs (fluoranthene, acenaphthene, naphthalene, chrysene, and anthracene). Isomeric pair ratios suggested biomass combustion and fossil fuel emissions as the main sources of PAHs. The toxic equivalency factors (TEFs) showed that carcinogenic potency (benzo[a]pyrene-equivalent concentration (B[a]P_eq) of PAH load in industrial and roadside soils was ～10 and ～6 times greater than the agricultural soil.     

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.     

Sphingobium sp. FB3 degrades a mixture of polycyclic aromatic hydrocarbons

A soil sample collected underneath a sewage pipe of the west side of Yangpu refining factory in Haikou city, Hainan Province, China was inoculated in minimum medium supplemented with fluoranthene. After 8 enrichment cycles, a bacterial consortium (Y12) was obtained through water-silicone oil dual system in the laboratory. The consortium Y12 could degrade a mixture of polycyclic aromatic hydrocarbons (PAHs) including phenanthrene, anthracene, fluoranthene, pyrene and benzo[a]pyrene. The consortium Y12 was repeatedly cultured for more than 40 circles, from which a bacterial strain FB3 was isolated. This strain was identified as a Sphingobium sp. through the 16S rDNA sequence alignment. Strain FB3 could degrade 99 ± 0.4%, 67 ± 2%, 97 ± 3%, 72 ± 8%, and 6 ± 2% (uncorrected degradation percentages) of phenanthrene, anthracene, fluoranthene and pyrene each at level of 100 mg L⁻¹ and benzo[a]pyrene at 10 mg L⁻¹, respectively, in 10 days, which the five PAHs were the sole carbon source as a mixture in minimum medium. The degradation percentages of phenanthrene, anthracene, fluoranthene, pyrene (each at level of 100 mg L⁻¹) and benzo[a]pyrene (10 mg L⁻¹) by consortium Y12 were 99 ± 0.1%, 65 ± 3%, 99 ± 0.3%, 79 ± 1% and 7 ± 6%, respectively, in 10 days. Strain FB3 could degrade those PAHs under a range of pH 5–9, being optimum at pH 7.     

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.     

Biotransformation of the high‐molecular weight polycyclic aromatic hydrocarbon (PAH) benzo[k]fluoranthene by Sphingobium sp. strain KK22 and identification of new products of non‐alternant PAH biodegradation by liquid chromatography electrospray ionization tandem mass spectrometry

A pathway for the biotransformation of the environmental pollutant and high‐molecular weight polycyclic aromatic hydrocarbon (PAH) benzo[k]fluoranthene by a soil bacterium was constructed through analyses of results from liquid chromatography negative electrospray ionization tandem mass spectrometry (LC/ESI(–)‐MS/MS). Exposure of Sphingobium sp. strain KK22 to benzo[k]fluoranthene resulted in transformation to four‐, three‐ and two‐aromatic ring products. The structurally similar four‐ and three‐ring non‐alternant PAHs fluoranthene and acenaphthylene were also biotransformed by strain KK22, and LC/ESI(–)‐MS/MS analyses of these products confirmed the lower biotransformation pathway proposed for benzo[k]fluoranthene. In all, seven products from benzo[k]fluoranthene and seven products from fluoranthene were revealed and included previously unreported products from both PAHs. Benzo[k]fluoranthene biotransformation proceeded through ortho‐cleavage of 8,9‐dihydroxy‐benzo[k]fluoranthene to 8‐carboxyfluoranthenyl‐9‐propenic acid and 9‐hydroxy‐fluoranthene‐8‐carboxylic acid, and was followed by meta‐cleavage to produce 3‐(2‐formylacenaphthylen‐1‐yl)‐2‐hydroxy‐prop‐2‐enoic acid. The fluoranthene pathway converged with the benzo[k]fluoranthene pathway through detection of the three‐ring product, 2‐formylacenaphthylene‐1‐carboxylic acid. Production of key downstream metabolites, 1,8‐naphthalic anhydride and 1‐naphthoic acid from benzo[k]fluoranthene, fluoranthene and acenaphthylene biotransformations provided evidence for a common pathway by strain KK22 for all three PAHs through acenaphthoquinone. Quantitative analysis of benzo[k]fluoranthene biotransformation by strain KK22 confirmed biodegradation. This is the first pathway proposed for the biotransformation of benzo[k]fluoranthene by a bacterium.     

Removal and transformation of high molecular weight polycyclic aromatic hydrocarbons in water by live and dead microalgae

The removal and transformation of seven high molecular weight polycyclic aromatic hydrocarbons (PAHs), namely benz[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, indeno[1,2,3-c,d]pyrene and benzo[g,h,i]perylene, by a freshwater microalga Selenastrum capricornutum under gold and white light irradiation was studied. The two light sources did not result in significant differences in the biodegradation of the selected PAHs in live algal cells, but white light was more effective in promoting photodegradation than was gold light in dead cells. The removal efficiency of seven PAHs, as well as the difference between live and dead microalgal cells, was PAH compound-dependent. Benz[a]anthracene and benzo[a]pyrene were highly transformed in live and dead algal cells, and dead cells displayed greater transformation levels than live cells. Further investigation comparing the transformation of single PAH compound, benzo[a]pyrene, by S. capricornutum and another green microalgal species, Chlorella sp., demonstrated that the transformation in dead cells was similar, indicating the process was algal-species independent. Dead algal cells most likely acted as a photosensitizer and accelerated the photodegradation of PAHs.     

Effect of Exposure Time,Contamination Level,and Type of PAH Compound on Biodegradation Capacity of Mangrove Sediment

Mangrove sediment had high natural attenuation potential with more than 50% of total PAHs being removed within 15 days. The efficiency in degrading PAHs varied with the declining order of phenanthrene (Phe), fluoranthene (Fla), and pyrene (Pyr). The Most Probable Number (MPN) of PAH-degrading bacteria in the PAH-contaminated slurries was 2 to 4 orders of magnitude higher than that in the non-contaminated mangrove slurries. The biodegradation ability of the indigenous microbial community in mangrove sediment slurry was significantly increased after exposure to polycyclic aromatic hydrocarbons. Such enhancement effect was dependent on the level and time of exposure, as well as the types of PAH compounds. The lowest contamination level of 3 mg kg^?1 was effective in promoting the degradation of Phe and Fla after seven days, but the enhancement effect for Pyr degradation was only found in the slurries exposed to contamination levels of 9 mg kg^?1 for 30 days, suggesting a threshold concentration of PAHs to stimulate growth and activity of pyrene-degrading bacteria. The contamination level higher than the threshold concentration did not lead to more degradation. The present study provides insights into the natural attenuation of PAH-contaminated mangrove sediments.     

Polynuclear Aromatic Hydrocarbons (PAHs) in fish from the Red Sea Coast of Yemen

A detailed analytical study using combined normal phase high pressure liquid chromatography (HPLC), gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) of Polynuclear Aromatic Hydrocarbons (PAHs) in fish from the Red Sea was undertaken. This investigation involves a preliminary assessment of the sixteen parent compounds issued by the U.S. Environmental Protection Agency(EPA). The study revealed measurable levels of Σ PAHs (the sum of three to five or six ring parent compounds) (49.2 ng g⁻¹ dry weight) and total PAHs (all PAH detected) (422.1 ng g⁻¹ dry weight) in edible muscle of fishes collected from the Red Sea. These concentrations are within the range of values reported for other comparable regions of the world. Mean concentrations for individual parent PAH in fish muscles were; naphthalene 19.5, biphenyl 4.6, acenaphthylene 1.0, acenaphthene 1.2, fluorene 5.5, phenanthrene 14.0, anthracene 0.8, fluoranthene 1.5, pyrene 1.8, benz(a)anthracene 0.4, chrysene 1.9, benzo(b)fluoranthene 0.5, benzo(k)fluoranthene 0.5, benzo(e)pyrene 0.9, benzo(a)pyrene 0.5, perylene 0.2, and indeno(1,2,3-cd)pyrene 0.1 ng g⁻¹ dry weight respectively. The Red Sea fish extracts exhibit the low molecular weight aromatics as well as the discernible alkyl-substituted species of naphthalene, fluorene, phenanthrene and dibenzothiophene. Thus, it was suggested that the most probable source of PAHs is oil contamination originating from spillages and/or heavy ship traffic. It was concluded that the presence of PAHs in the fish muscles is not responsible for the reported fish kill phenomenon. However, the high concentrations of carcinogenic chrysene encountered in these fishes should be considered seriously as it is hazardous to human health. Based on fish consumption by Yemeni‘s population it was calculated that the daily intake of total carcinogens were 0.15 μg/person/day. This revised version was published online in August 2006 with corrections to the Cover Date.     

Pleiotropic and Epistatic Behavior of a Ring-Hydroxylating Oxygenase System in the Polycyclic Aromatic Hydrocarbon Metabolic Network from Mycobacterium vanbaalenii PYR-1

Despite the considerable knowledge of bacterial high-molecular-weight (HMW) polycyclic aromatic hydrocarbon (PAH) metabolism, the key enzyme(s) and its pleiotropic and epistatic behavior(s) responsible for low-molecular-weight (LMW) PAHs in HMW PAH-metabolic networks remain poorly understood. In this study, a phenotype-based strategy, coupled with a spray plate method, selected a Mycobacterium vanbaalenii PYR-1 mutant (6G11) that degrades HMW PAHs but not LMW PAHs. Sequence analysis determined that the mutant was defective in pdoA2, encoding an aromatic ring-hydroxylating oxygenase (RHO). A series of metabolic comparisons using high-performance liquid chromatography (HPLC) analysis revealed that the mutant had a lower rate of degradation of fluorene, anthracene, and pyrene. Unlike the wild type, the mutant did not produce a color change in culture media containing fluorene, phenanthrene, and fluoranthene. An Escherichia coli expression experiment confirmed the ability of the Pdo system to oxidize biphenyl, the LMW PAHs naphthalene, phenanthrene, anthracene, and fluorene, and the HMW PAHs pyrene, fluoranthene, and benzo[a]pyrene, with the highest enzymatic activity directed toward three-ring PAHs. Structure analysis and PAH substrate docking simulations of the Pdo substrate-binding pocket rationalized the experimentally observed metabolic versatility on a molecular scale. Using information obtained in this study and from previous work, we constructed an RHO-centric functional map, allowing pleiotropic and epistatic enzymatic explanation of PAH metabolism. Taking the findings together, the Pdo system is an RHO system with the pleiotropic responsibility of LMW PAH-centric hydroxylation, and its epistatic functional contribution is also crucial for the metabolic quality and quantity of the PAH-MN.     

Adsorption of PAHs on the Sediments from the Yellow River Delta as a Function of Particle Size and Salinity

In a seawater environment, the particle size of sediment and salinity play an important role in the adsorption behaviors of polycyclic aromatic hydrocarbons (PAHs) on sediment. In this study, batch adsorption experiments were carried out with the sediments from the Yellow River Delta (YRD) to explore the effect of particle size and salinity on the adsorption behaviors of phenanthrene (Phe), fluoranthene (Fla), and pyrene (Pyr). Adsorption isotherms of PAHs on different-sized sediments can be described by a Freundlich model with the correlation coefficients ranging from 0.96 to 0.99. The adsorption capacity of PAHs was in reverse proportion to the particle size of the sediments and in direct proportion to salinity. The sediments with smaller particle size possessed higher content of aromatic and fat components, which had strong adsorption capacity toward PAHs. Salinity influenced the adsorption behaviors of PAHs by changing the solubility of PAHs and the physicochemical properties of the sediments. The salting-out constants of Phe, Fla, and Pyr were in the range of 0.292 to 0.296, 0.230 to 0.289, and 0.293 to 0.307 l/mol, respectively. These research findings are of importance to an assessment of the fate and transport of PAHs in seawater-sediment systems.     

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中的定殖存活能力可能影响了生物强化效果。采用灭菌土壤排除土著微生物的竞争排斥作用,研究了真菌菌丝对生物强化降解的影响,发现在蒽污染土壤中,真菌菌丝的迁移作用显著提高了细菌鞘脂菌NS7对污染物的矿化率,从1.75%提高到5.91%;而在苯并[a]蒽灭菌污染土壤中,接种糙皮侧耳却没有发现苯并[a]蒽矿化率提高的现象,表明自然土壤中真菌强化降解苯并[a]蒽的作用可能是源于真菌菌丝促进污染物和土著降解菌的接触,而非直接来自真菌本身。[结论] 细菌能够很好地降解低环种类多环芳烃,而真菌对高环种类多环芳烃降解效果较好。真菌可能通过菌丝促进土著微生物在土壤中的迁移,增大多环芳烃和土著降解菌的接触,从而促进了多环芳烃降解。研究加深了对多环芳烃污染土壤生物强化修复的认识,对发展基于真菌-细菌协同作用的生物强化与调控技术提供理论指导。     

Effects of Crude Oil Exposure on Bioaccumulation of Polycyclic Aromatic Hydrocarbons and Survival of Adult and Larval Stages of Gelatinous Zooplankton

Gelatinous zooplankton play an important role in marine food webs both as major consumers of metazooplankton and as prey of apex predators (e.g., tuna, sunfish, sea turtles). However, little is known about the effects of crude oil spills on these important components of planktonic communities. We determined the effects of Louisiana light sweet crude oil exposure on survival and bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) in adult stages of the scyphozoans Pelagia noctiluca and Aurelia aurita and the ctenophore Mnemiopsis leidyi, and on survival of ephyra larvae of A. aurita and cydippid larvae of M. leidyi, in the laboratory. Adult P. noctiluca showed 100% mortality at oil concentration ≥20 µL L⁻¹ after 16 h. In contrast, low or non-lethal effects were observed on adult stages of A. aurita and M. leidyi exposed at oil concentration ≤25 µL L⁻¹ after 6 days. Survival of ephyra and cydippid larva decreased with increasing crude oil concentration and exposition time. The median lethal concentration (LC₅₀) for ephyra larvae ranged from 14.41 to 0.15 µL L⁻¹ after 1 and 3 days, respectively. LC₅₀ for cydippid larvae ranged from 14.52 to 8.94 µL L⁻¹ after 3 and 6 days, respectively. We observed selective bioaccumulation of chrysene, phenanthrene and pyrene in A. aurita and chrysene, pyrene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, and benzo[a]anthracene in M. leidyi. Overall, our results indicate that (1) A. aurita and M. leidyi adults had a high tolerance to crude oil exposure compared to other zooplankton, whereas P. noctiluca was highly sensitive to crude oil, (2) larval stages of gelatinous zooplankton were more sensitive to crude oil than adult stages, and (3) some of the most toxic PAHs of crude oil can be bioaccumulated in gelatinous zooplankton and potentially be transferred up the food web and contaminate apex predators.     

Phenanthrene stimulates the degradation of pyrene and fluoranthene by <Emphasis Type="Italic">Burkholderia</Emphasis> sp. VUN10013

Pyrene and fluoranthene, when supplied as the sole carbon source, were not degraded by Burkholderia sp. VUN10013. However, when added in a mixture with phenanthrene, both pyrene and fluoranthene were degraded in liquid broth and soil. The amounts of pyrene and fluoranthene in liquid media (initial concentrations of 50 mg l⁻¹ each) decreased to 42.1% and 41.1%, respectively, after 21 days. The amounts of pyrene and fluoranthene in soil (initial concentrations of 75 mg kg⁻¹ dry soil each) decreased to 25.8% and 12.1%, respectively, after 60 days. None of the high molecular weight (HMW) polycylic aromatic hydrocarbons (PAHs) tested adversely affected phenanthrene degradation by this bacterial strain and the amount of phenanthrene decreased rapidly within 3 and 15 days of incubation in liquid broth and soil, respectively. Anthracene also stimulated the degradation of pyrene or fluoranthene by Burkholderia sp. VUN10013, but to a lesser extent than phenanthrene. The extent of anthracene degradation decreased in the presence of these HMW PAHs.     

Degradation of a mixture of high‐molecular‐weight polycyclic aromatic hydrocarbons by a Mycobacterium strain PYR‐1

Mycobacterium sp. PYR‐1, which was previously shown to mineralize several individual polycyclic aromatic hydrocarbons (PAHs), simultaneously degraded phenanthrene, anthracene, fluoranthene, pyrene and benzo[a]pyrene in a six‐component synthetic mixture. Chrysene was not degraded significantly. When provided with a complex carbon source, Mycobacterium sp. PYR‐1 degraded greater than 74% of the total PAH mixture during 6 d of incubation. Mycobacterium sp. PYR‐1 appeared to preferentially degrade phenanthrene. No significant difference in degradation rates was observed between fluoranthene and pyrene. Anthracene degradation was slightly delayed but, once initiated, proceeded at a constant rate. Benzo[a]pyrene was degraded slowly. Degradation of a crude mixture of benzene‐soluble PAHs from contaminated sediments resulted in a 47% reduction of the material in 6 d compared with that of autoclaved controls. Experiments using an environmental microcosm test system indicated that mineralization rates of individual ¹⁴C‐labeled compounds were significantly lower in the mixtures than in equivalent doses of these compounds alone. Mineralization of the complete mixture was estimated conservatively to be between 49.7 and 53.6% and was nearly 50% in 30 d of incubation when all compounds were radiolabeled. These results strengthen the argument for the potential application of Mycobacterium sp. PYR‐1 for bioremediation of PAH‐contaminated wastes.     

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.