The metabolism of fluoranthene by a species ofMycobacterium

The shifting research landscape for PAH bioremediation in water environment: a bibliometric analysis on three decades of development

Polycyclic aromatic hydrocarbons (PAHs) with their carcinogenic, teratogenic, and mutagenic effects can cause great damage to the ecosystem and public health when present in water. With bioremediation, PAH contamination in water environment can be greatly reduced in an eco-friendly manner. It has thus become the research focus for many environmental scientists. In this study, a bibliometric analysis on three-decade (1990-2022) development of PAH bioremediation in water environment was conducted from temporal and spatial dimensions using CiteSpace. A total of 2480 publications, obtained from Web of Science core collection database, were used to explore the basic characteristics, hotspots, and prospects of the research area. The results showed that (1) bioremediation/biodegradation of PAHs in water environment has been getting researchers' attention since 1990, and is gaining even more traction as time goes on. (2) In terms of countries, China and the USA were the major contributors in this research area, while at the institutional level, the Chinese Academy of Sciences has produced the most research results. However, international cooperation across regions was lacking in the field. (3) Environment Science and Technology, Chemosphere, Applied and Environment Microbiology, Journal of Hazardous Materials, and Environment Pollution were the 5 most cited journals in this field. (4) There were three major stages the field has gone through, each with distinct research hotspots, including initial stage (1990-1994), mechanism investigation (1995-2000), and application exploration (2001-2010; 2011-2022). Finally, research perspectives were proposed, covering three directions, namely, bioavailability, immobilization, and viable but nonculturable (VBNC) bacteria.

Biodegradation of phenanthrene as a model hydrocarbon: Power display of a super-hydrophobic halotolerant enriched culture derived from a saline-sodic soil

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Bacterial isolates are found to be both hydrophobe and halotolerant.

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This bacterial enriched culture degraded 87.66% of the phenanthrene after 10 days.

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The high hydrophobicity of cells is the main rationale behind phenanthrene degradation.

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Both alfalfa and barley seeds can germinate after biodegradation of phenanthrene in the contaminated soil.

In this study, after evaluating the degradation activity of enriched cultures from four crude oil-contaminated soils in mineral salt medium, the most efficient ones were selected for further studies. The chemical analysis of cell-free extract containing phenanthrene by HPLC suggested the superior enriched culture was able to degrade 87.66% of phenanthrene at the concentration of 40 mg L-1 within 10 days. This experiment was done under optimal conditions (37 °C, 10% salinity, and pH around 7 to 7.5). The 16S rRNA sequencing of isolates from this superior enriched culture indicated the highest similarity to Acidovorax delafieldii (Q-SH3), Bacillus hwajinpoensis (Q-SH12), and Bacillus rhizosphaerae (Q-SH14). After biodegradation of phenanthrene in liquid medium, the extracts were analyzed to measure barley and alfalfa germination. Results showed a lower level of toxicity to the seeds, hence this enriched culture could be used for bioremediation of saline environments contaminated by phenanthrene and other similar compounds.

Preparation of dihydroxy polycyclic aromatic hydrocarbons and activities of two dioxygenases in the phenanthrene degradative pathway

Dihydroxy phenanthrene, fluoranthene, and pyrene derivatives are intermediates in the bacterial catabolism of the corresponding parent polycyclic aromatic hydrocarbon (PAH). Ring-opening of the dihydroxy species followed by a series of enzyme-catalyzed reactions generates metabolites that funnel into the Krebs Cycle with the eventual production of carbon dioxide and water. One complication in delineating these pathways and harnessing them for useful purposes is that the initial enzymatic processing produces multiple dihydroxy PAHs with multiple ring opening possibilities and products. As part of a systematic effort to address this issue, eight dihydroxy species were synthesized and characterized as the dimethoxy or diacetate derivatives. Several dihydroxy compounds were examined with two dioxygenases in the phenanthrene degradative pathway in Mycobacterium vanbaalenii PYR-1. One, 3,4-dihydroxyphenanthrene, was processed by PhdF with a k_cat/K_m of 6.0 × 10⁶ M^-1s^-1, a value that is consistent with the annotated function of PhdF in the pathway. PhdI processed 1-hydroxy-2-naphthoate with a k_cat/K_m of 3.1 × 10⁵ M^-1s^-1, which is also consistent with the proposed role in the pathway. The observations provide the first biochemical evidence for these two reactions in M. vanbaalenii PYR-1 and, to the best of our knowledge, the first biochemical evidence for the reaction of PhdF with 3,4-dihydroxyphenanthrene. Although PhdF is upregulated in the presence of pyrene, it did not process two dihydroxypyrenes. Methodology was developed for product analysis of the extradiol dioxygenases.

Structural Characterization of the Hydratase-Aldolases, NahE and PhdJ: Implications for the Specificity, Catalysis, and N-Acetylneuraminate Lyase Subgroup of the Aldolase Superfamily

NahE and PhdJ are bifunctional hydratase-aldolases in bacterial catabolic pathways for naphthalene and phenanthrene, respectively. Bacterial species with these pathways can use polycyclic aromatic hydrocarbons (PAHs) as sole sources of carbon and energy. Because of the harmful properties of PAHs and their widespread distribution and persistence in the environment, there is great interest in understanding these degradative pathways, including the mechanisms and specificities of the enzymes found in the pathways. This knowledge can be used to develop and optimize bioremediation techniques. Although hydratase-aldolases catalyze a major step in the PAH degradative pathways, their mechanisms are poorly understood. Sequence analysis identified NahE and PhdJ as members of the N-acetylneuraminate lyase (NAL) subgroup in the aldolase superfamily. Both have a conserved lysine and tyrosine (for Schiff base formation) as well as a GXXGE motif (to bind the pyruvoyl carboxylate group). Herein, we report the structures of NahE, PhdJ, and PhdJ covalently bound to substrate via a Schiff base. Structural analysis and dynamic light scattering experiments show that both enzymes are tetramers. A hydrophobic helix insert, present in the active sites of NahE and PhdJ, might differentiate them from other NAL subgroup members. The individual specificities of NahE and PhdJ are governed by Asn-281/Glu-285 and Ser-278/Asp-282, respectively. Finally, the PhdJ complex structure suggests a potential mechanism for hydration of substrate and subsequent retro-aldol fission. The combined findings fill a gap in our mechanistic understanding of these enzymes and their place in the NAL subgroup.

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.

Degradation of fluoranthene by a newly isolated strain of Herbaspirillum chlorophenolicum from activated sludge

A fluoranthene-degrading bacterial strain FA1 was isolated from activated sludge and identified as Herbaspirillum chlorophenolicum, a newfound bacterial species that can grow well on fluoranthene as sole carbon and energy source. The kinetic characteristic of strain FA1 was tested in the aqueous model system (AMS) and the effects of nonionic surfactants on fluoranthene biodegradation in the AMS were then investigated. Tween 80 exhibited the best solubilization capacity for fluoranthene among three surfactants and its bioavailability decreased with an increase in its concentration and its degradation kinetics fit well with the first-order of power index model. The biotransformation of fluoranthene was greatly improved by Tween 80, and 58.5% fluoranthene degradation was obtained as Tween 80 was 100 mg/l. However, the bioavailability of fluoranthene decreased gradually with the increase of Tween 80 concentration. Bioremediation tests for fluoranthene in soil-water system were designed further to examine the degrading ability of strain FA1 with the presence of indigenous flora or not. The measurements showed that in the presence of indigenous flora, the optimum 30-day fluoranthene degradation in soil-water system reached 77.4%. Evidently, strain FA1 seems both efficient and high-effective and deserves further exploration on the enhanced bioremediation technologies for the treatment of fluoranthene-polluted soil.

Microcalorimetric investigation of the toxic action of pyrene on the growth of PAH-degrading bacteria Acinetobacter junii

A multi-channel thermal activity microcalorimeter was used to determine the pyrene-induced toxic effect on two polycyclic aromatic hydrocarbon (PAH)-degrading bacteria Acinetobacter junii (A. junii) and Bacillus subtilis (B. subtilis). Power-time curves were analyzed and calorimetric parameters including growth rate constant (k), half inhibitory concentration (IC50) and total thermal effect (QT) were obtained. A. junii and B. subtilis were completely inhibited when the concentration of pyrene reached 400 and 160 microg mL(-1), respectively. The relationships between the calorimetric parameters and concentration of pyrene were studied. The growth rate of A. junii decreased with the increase in pyrene concentration at 50-200 microg mL(-1). The growth of biomass for A. junii at various concentrations of pyrene was determined. The count of A. junii after 8 day's incubation reached maximum irrespective of the initial pyrene concentrations ranging from 50 to 200 microg mL(-1) and the smallest stimulative action of pyrene was at 200 microg mL(-1). The variations of biomass during the growth of A. junii were consistent with the microcalorimetric data, indicating that microcalorimetry can be an effective technique to investigate the effect of pyrene on microorganisms.

Remediation of PAH contaminated soils: application of a solid-liquid two-phase partitioning bioreactor

The feasibility of a two-step treatment process has been assessed at laboratory scale for the remediation of soil contaminated with a model mixture of polycyclic aromatic hydrocarbons (PAHs) (phenanthrene, pyrene, and fluoranthene). The initial step of the process involved contacting contaminated soil with thermoplastic, polymeric pellets (polyurethane). The ability of three different mobilizing agents (water, surfactant (Biosolve) and isopropyl alcohol) to enhance recovery of PAHs from soil was investigated and the results were compared to the recovery of PAHs from dry soil. The presence of isopropyl alcohol had the greatest impact on PAH recovery with approximately 80% of the original mass of PAHs in the soil being absorbed by the polymer pellets in 48 h. The second stage of the suggested treatment involved regeneration of the PAH loaded polymers via PAH biodegradation, which was carried out in a solid-liquid two-phase partitioning bioreactor. In addition to the PAH containing polymer pellets, the bioreactor contained a microbial consortium that was pre-selected for its ability to degrade the model PAHs and after a 14 d period approximately 78%, 62% and 36% of phenanthrene, pyrene, and fluoranthene, respectively, had been desorbed from the polymer and degraded. The rate of phenanthrene degradation was shown to be limited by mass transfer of phenanthrene from the polymer pellets. In case of pyrene and fluoranthene a combination of mass transfer and biodegradation rate might have been limiting.

Degradation of benz[a]anthracene by Mycobacterium vanbaalenii strain PYR-1

Cultures of Mycobacterium vanbaalenii strain PYR-1 grown in mineral salts medium and nutrients in the presence of benz[a]anthracene metabolized 15% of the added benz[a]anthracene after 12 days of incubation. Neutral and acidic ethyl acetate extractable metabolites were isolated and characterized by high performance liquid chromatography (HPLC) and uv-visible absorption, gas chromatography/mass (GC/MS) and nuclear magnetic resonance (NMR) spectral analysis. Trimethylsilylation of the metabolites followed by GC/MS analysis facilitated identification of metabolites. The characterization of metabolites indicated that M. vanbaalenii initiated attack of benz[a]anthracene at the C-1,2-, C-5,6-, C-7,12- and C-10,11-positions to form dihydroxylated and methoxylated intermediates. The major site of enzymatic attack was in the C-10, C-11 positions. Subsequent ortho- and meta-cleavage of each of the aromatic rings led to the accumulation of novel ring-fission metabolites in the medium. The major metabolites identified were 3-hydrobenzo[f]isobenzofuran-1-one (3.2%), 6-hydrofuran[3,4-g]chromene-2,8-dione (1.3%), benzo[g]chromene-2-one (1.7%), naphtho[2,1-g]chromen-10-one (48.1%), 10-hydroxy-11-methoxybenz[a]anthracene (9.3%), and 10,11-dimethoxybenz[a]anthracene (36.4%). Enzymatic attack at the C-7 and C-12 positions resulted in the formation of benz[a]anthracene-7,12-dione, 1-(2-hydroxybenzoyl)-2-naphthoic acid, and 1-benzoyl-2-naphthoic acid. A phenyl-naphthyl metabolite, 3-(2-carboxylphenyl)-2-naphthoic acid, was formed when M. vanbaalenii was incubated with benz[a]anthracene cis-5,6-dihydrodiol, indicating ortho-cleavage of 5,6-dihydroxybenz[a]anthracene. A minor amount of 5,6-dimethoxybenz[a]anthracene was also formed. The data extend and propose novel pathways for the bacterial metabolism of benz[a]anthracene.

Effect of Mycobacterium sp. strain CH1 and mycobacterium sp. strain CH2 on the degradation of four-ring creosote compounds

The influence of nutrients, Mycobacterium sp. strain CH1 and Mycobacterium sp. strain CH2 on the degradation of aged creosote hydrocarbon contaminants was investigated. The Mycobacterium sp. strain CH2 showed the highest positive influence on the degradation of three- and four-ring PAH compounds. The addition of Mycobacterium sp. strain CH1 had the second highest measured positive influence on the degradation of four-ring compounds. Soluble nitrogen and phosphorus also increased the degradation of aged creosote compounds in the contaminated soil. The addition of bacteria decreased the number of measured bacterial species, indicating competition for limited nutrients in the soil.

Regio- and stereoselective metabolism of 7,12-dimethylbenz[a]anthracene by Mycobacterium vanbaalenii PYR-1

The degradation of 7,12-dimethylbenz[a]anthracene (DMBA), a carcinogenic polycyclic aromatic hydrocarbon, by cultures of Mycobacterium vanbaalenii PYR-1 was studied. When M. vanbaalenii PYR-1 was grown in the presence of DMBA for 136 h, high-pressure liquid chromatography (HPLC) analysis showed the presence of four ethyl acetate-extractable compounds and unutilized substrate. Characterization of the metabolites by mass and nuclear magnetic resonance spectrometry indicated initial attack at the C-5 and C-6 positions and on the methyl group attached to C-7 of DMBA. The metabolites were identified as cis-5,6-dihydro-5,6-dihydroxy-7,12-dimethylbenz[a]anthracene (DMBA cis-5,6-dihydrodiol), trans-5,6-dihydro-5,6-dihydroxy-7,12-dimethylbenz[a]anthracene (DMBA trans-5,6-dihydrodiol), and 7-hydroxymethyl-12-methylbenz[a]anthracene, suggesting dioxygenation and monooxygenation reactions. Chiral stationary-phase HPLC analysis of the dihydrodiols showed that DMBA cis-5,6-dihydrodiol had 95% 5S,6R and 5% 5R,6S absolute stereochemistry. On the other hand, the DMBA trans-5,6-dihydrodiol was a 100% 5S,6S enantiomer. A minor photooxidation product, 7,12-epidioxy-7,12-dimethylbenz[a]anthracene, was also formed. The results demonstrate that M. vanbaalenii PYR-1 is highly regio- and stereoselective in the degradation of DMBA.

Degradation of phenanthrene and anthracene by cell suspensions of Mycobacterium sp. strain PYR-1

Cultures of Mycobacterium sp. strain PYR-1 were dosed with anthracene or phenanthrene and after 14 days of incubation had degraded 92 and 90% of the added anthracene and phenanthrene, respectively. The metabolites were extracted and identified by UV-visible light absorption, high-pressure liquid chromatography retention times, mass spectrometry, (1)H and (13)C nuclear magnetic resonance spectrometry, and comparison to authentic compounds and literature data. Neutral-pH ethyl acetate extracts from anthracene-incubated cells showed four metabolites, identified as cis-1,2-dihydroxy-1,2-dihydroanthracene, 6,7-benzocoumarin, 1-methoxy-2-hydroxyanthracene, and 9,10-anthraquinone. A novel anthracene ring fission product was isolated from acidified culture media and was identified as 3-(2-carboxyvinyl)naphthalene-2-carboxylic acid. 6,7-Benzocoumarin was also found in that extract. When Mycobacterium sp. strain PYR-1 was grown in the presence of phenanthrene, three neutral metabolites were identified as cis- and trans-9,10-dihydroxy-9,10-dihydrophenanthrene and cis-3,4-dihydroxy-3,4-dihydrophenanthrene. Phenanthrene ring fission products, isolated from acid extracts, were identified as 2,2'-diphenic acid, 1-hydroxynaphthoic acid, and phthalic acid. The data point to the existence, next to already known routes for both gram-negative and gram-positive bacteria, of alternative pathways that might be due to the presence of different dioxygenases or to a relaxed specificity of the same dioxygenase for initial attack on polycyclic aromatic hydrocarbons.

Diverse oxygenations catalyzed by carbazole 1,9a-dioxygenase from Pseudomonas sp. Strain CA10

Carbazole 1,9a-dioxygenase (CARDO) from Pseudomonas sp. strain CA10 is a multicomponent enzyme that catalyzes the angular dioxygenation of carbazole, dibenzofuran, and dibenzo-p-dioxin. It was revealed by gas chromatography-mass spectrometry and 1H and 13C nuclear magnetic resonance analyses that xanthene and phenoxathiin were converted to 2,2',3-trihydroxydiphenylmethane and 2,2',3-trihydroxydiphenyl sulfide, respectively. Thus, for xanthene and phenoxathiin, angular dioxygenation by CARDO occurred at the angular position adjacent to the oxygen atom to yield hetero ring-cleaved compounds. In addition to the angular dioxygenation, CARDO catalyzed the cis dihydroxylation of polycyclic aromatic hydrocarbons and biphenyl. Naphthalene and biphenyl were converted by CARDO to cis-1, 2-dihydroxy-1,2-dihydronaphthalene and cis-2,3-dihydroxy-2, 3-dihydrobiphenyl, respectively. On the other hand, CARDO also catalyzed the monooxygenation of sulfur heteroatoms in dibenzothiophene and of the benzylic methylenic group in fluorene to yield dibenzothiophene-5-oxide and 9-hydroxyfluorene, respectively. These results indicate that CARDO has a broad substrate range and can catalyze diverse oxygenation: angular dioxygenation, cis dihydroxylation, and monooxygenation. The diverse oxygenation catalyzed by CARDO for several aromatic compounds might reflect the differences in the binding of the substrates to the reaction center of CARDO.

Degradation of fluoranthene by Pasteurella sp. IFA and Mycobacterium sp. PYR-1:isolation and identification of metabolites

The findings from a biodegradability study of fluoranthene using two pure bacterial strains, Pasteurella sp. IFA (B-2) and Mycobacterium sp. PYR-1 (AM) are reported. Of total fluoranthene, 24% (B-2) and 46% (AM) was biodegraded in an aqueous medium during 14 d of incubation at room temperature. During this period the bacteria were capable of mineralizing approximately two-thirds (B-2) and four-fifths (AM) of biodegraded fluoranthene to CO2, while one-third (B-2) and one-fifth (AM) of the original fluoranthene remained as stable metabolic products. These metabolites were isolated using liquid-liquid extraction and identified using gas chromatography-mass spectrometry (GC-MS) and derivatization techniques. Two metabolites (9-fluorenone-1-carboxylic acid and 9-fluorenone) were identified by GC-MS directly, while the metabolites 9-fluorenone-1-carboxylic acid, 9-hydroxyfluorene, 9-hydroxy-1-fluorene-carboxylic acid, 2-carboxybenzaldehyde, benzoic acid and phenylacetic acid were determined in their derivatized forms. From the identified metabolites, a fluoranthene biodegradation pathway was proposed for Pasteurella sp. IFA.

The microbiological fate of polycyclic aromatic hydrocarbons: carbon and oxygen balances for bacterial degradation of model compounds

A series of pure bacterial strains belonging mainly to the Rhodococcus and Pseudomonas genera were grown on one of the following polycyclic aromatic hydrocarbons (PAH) supplied as sole carbon and energy source; naphthalene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene. In each case, a quantitative evaluation of the carbon repartition of the PAH degraded into CO2, biomass and water-soluble metabolites was carried out. In addition, the kinetics of oxygen consumption and of water-soluble metabolite accumulation during PAH biodegradation was followed with respirometric equipment. Satisfactory carbon balances were obtained and the data correlated well with oxygen consumption values. The results show that growth on PAH presents high mineralization yields (from 56% to 77% of carbon) and sizeable production of biomass (from 16% to 35% of carbon) and limited but significant accumulation of metabolites (from 5% to 23% of carbon). The mineralization yields were higher and biomass yields lower in the case of higher PAH. Some differences between strains were also observed.

Growth of rhodococcus S1 on anthracene

Three slow-growing bacteria were isolated from a mixed culture enriched for growth on anthracene, using creosote-contaminated soil as the inoculum. Organisms were shown to use anthracene by the production of a clear zone around the colony after a mineral salts agar plate was sprayed with anthracene. All three bacteria were nonmotile, nonsporulating, gram-positive rods and stained acid-fast. Physiological and biochemical tests, GC content, and cell wall lipid patterns of whole cell methanolysates indicated that they belonged to the Nocardia-Mycobacterium-Rhodococcus group. On the basis of these characteristics and pyrolysis gas chromatography, they were assigned to the genus Rhodococcus. Growth of the isolates was slow on crystalline anthracene, giving a doubling time of 1.5-3 days, and they grew mainly on the crystal surface. When anthracene was supplied by precipitation from a solvent, doubling time was reduced to 1 day. All three isolates mineralized anthracene but not phenanthrene or naphthalene, nor could they grow on naphthalene, phenanthrene, fluorene, fluoranthene, acenaphthene, pyrene, chrysene, or naphthacene as sole carbon source. One isolate, Rhodococcus S1, was able to use 2-methylanthracene or 2-chloroanthracene as carbon source but not 1- or 9-substituted analogs. These results suggest that the initial enzyme attacking anthracene in these isolates has a narrow substrate specificity.

Cloning and analysis of the genes for polycyclic aromatic hydrocarbon degradation

Bacterial degradation of polycyclic aromatic hydrocarbons initially proceeds through monooxygenase or dioxygenase attack on the aromatic ring. The dihydroxylated compounds formed are substrates for ring cleavage and further catabolism to tricarboxylic acid cycle intermediates. A number of microbial strains, both gram positive and gram negative, have been isolated that have the metabolic capability to degrade polycyclic aromatic hydrocarbons to carbon dioxide and water. In addition, many of these strains have the ability to cometabolize structurally similar aromatic compounds that may not normally serve as metabolic inducers or as carbon sources. The genes from several of these strains have been cloned for the purpose of analyzing in more detail their structure and function. The cloned genes were used to determine the range of substrates that can be metabolized by the genetically encoded pathway. For instance, the cloned genes from Pseudomonas sp. XPW-2 placed in E. coli encoded for the oxidation of such polycyclic aromatic hydrocarbons as naphthalene, biphenyl, anthracene, phenanthrene, acenaphthylene, fluorene, fluoranthene, chrysene, and pyrene. The cloned genes were also used as genetic probes to determine the degree of homology, if any, there is between different microbial strains capable of degrading polycyclic aromatic hydrocarbons. These experiments indicated significant homology among the class of terrestrial naphthalene and phenanthrene-degrading strains. Nevertheless, little homology was seen across species lines or among strains capable of degrading higher molecular weight polycyclic aromatic hydrocarbons. This indicates that there is a diversity of genetically distinct pathways for polycyclic aromatic hydrocarbon degradation.

Degradation of phenanthrene, fluorene, fluoranthene, and pyrene by a Mycobacterium sp

Mycobacterium sp. strain BB1 was isolated from a former coal gasification site. It was able to utilize phenanthrene, pyrene, and fluoranthene as sole sources of carbon and energy and to degrade fluorene cometabolically. Exponential growth with solid phenanthrene, pyrene, and fluoranthene was obtained in fermentor cultures. The growth rates were 0.069, 0.056, and 0.040 h-1, respectively. Several metabolites of phenanthrene and fluorene metabolism were identified.

Identification of metabolites from degradation of naphthalene by a Mycobacterium sp

A Mycobacterium sp. isolated from oil-contaminated sediments was previously shown to mineralize 55% of the added naphthalene to carbon dioxide after 7 days of incubation. In this paper, we report the initial steps of the degradation of naphthalene by a Mycobacterium sp. as determined by isolation of metabolites and incorporation of oxygen from 18O2 into the metabolites. The results indicate that naphthalene is initially converted to cis- and trans-1,2-dihydroxy-1,2-dihydronaphthalene by dioxygenase and monooxygenase catalyzed reactions, respectively. The ratio of the cis to trans-naphthalene dihydrodiol isomers was approximately 25: 1. Thin layer and high pressure liquid chromatographic and mass spectrometric techniques indicated that besides the cis- and trans-1,2-dihydroxy-1,2-dihydronaphthalene, minor amounts of ring cleavage products salicylate and catechol were also formed. Thus the formation of both cis and trans-naphthalene dihydrodiols by the Mycobacterium sp. is unique. The down-stream reactions to ring cleavage products proceed through analogous dioxygenase reactions previously reported for the bacterial degradation of naphthalene.