Evidence for significantly enhancing reduction of Azo dyes in Escherichia coli by expressed cytoplasmic Azoreductase (AzoA) of Enterococcus faecalis

Although cytoplasmic azoreductases have been purified and characterized from various bacteria, little evidence demonstrating that these azoreductases are directly involved in azo dye reduction in vivo is known. In order to evaluate the contribution of the enzyme to azo dye reduction in vivo, experiments were conducted to determine the effect of a recombinant cytoplasmic azoreductase (AzoA) from Enterococcus faecalis expressed in Escherichia coli on the rate of metabolism of Methyl Red, Ponceau BS and Orange II. The intact cells that contained IPTG induced AzoA had a higher rate of dye reduction with increases of 2 (Methyl Red), 4 (Ponceau BS) and 2.6 (Orange II)-fold compared to noninduced cells, respectively. Metabolites of Methyl Red isolated from induced cultures were identified as N,N-dimethyl-p-phenylenediamine and 2-aminobenzoic acid through liquid chromatography electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) analyses. In conclusion, our data demonstrate that AzoA from Ent. faecalis is capable of increasing the reduction of azo dyes in intact E. coli cells and that cytoplasmic azoreductase is involved in bacterial dye degradation in vivo.

Acetylation of fluoroquinolone antimicrobial agents by an Escherichia coli strain isolated from a municipal wastewater treatment plant

AIMS

To isolate environmental bacteria capable of transforming fluoroquinolones to inactive molecules.

METHODS AND RESULTS

Bacteria were isolated from the aerobic liquor of a wastewater treatment plant on a medium containing norfloxacin (100 mg l(-1)). Twenty-two isolates were highly resistant (minimal inhibitory concentration: 6.25-200 microg ml(-1)) to five fluoroquinolones and six of them were positive by PCR amplification for the aminoglycoside resistance gene aac(6')-Ib. Of these, only Escherichia coli strain LR09 had the ciprofloxacin-acetylating variant gene aac(6')-Ib-cr; HPLC and mass spectrometry showed that this strain transformed both ciprofloxacin and norfloxacin by N-acetylation. This bacterium also had mutations in the quinolone-resistance determining regions of the gyrA and parC genes.

CONCLUSIONS

An E. coli isolate from wastewater, which possessed at least two distinct fluoroquinolone resistance mechanisms, inactivated ciprofloxacin and norfloxacin by N-acetylation.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report of N-acetylation of fluoroquinolones by an aac(6')-Ib-cr-containing bacterium from an environmental source.

Identification of metabolites produced from N-phenylpiperazine by Mycobacterium spp

Mycobacterium sp. 7E1B1W and seven other mycobacterial strains known to degrade hydrocarbons were investigated to determine their ability to metabolize the piperazine ring, a substructure found in many drugs. Cultures were grown at 30 degrees C in tryptic soy broth and dosed with 3.1 mM N-phenylpiperazine hydrochloride; samples were removed at intervals and extracted with ethyl acetate. Two metabolites were purified from each of the extracts by high-performance liquid chromatography; they were identified by mass spectrometry and (1)H nuclear magnetic resonance spectroscopy as N-(2-anilinoethyl)acetamide and N-acetyl-N'-phenylpiperazine. The results show that mycobacteria have the ability to acetylate piperazine rings and cleave carbon-nitrogen bonds.

Oxidation of phenothiazine and phenoxazine by Cunninghamella elegans

1. To determine the ability of fungi to metabolize sulphur- and oxygen-containing azaarenes, Cunninghamella elegans ATCC 9245 was grown in 125-ml flasks containing fluid Sabouraud medium. The cultures and controls were incubated at 28 degrees C with shaking and dosed with 16.7 mM phenothiazine or phenoxazine. After incubation for 72h, the mycelia and filtrates were extracted with ethyl acetate and the combined residues analysed by high-performance liquid chromatography. Residual phenothiazine and phenoxazine were 21 and 22%, respectively, of the total UV absorbance at 254 nm. 2. The metabolites were identified by mass spectrometry and proton nuclear magnetic resonance spectroscopy. The fungus oxidized phenothiazine to phenothiazine sulphoxide, 3-hydroxyphenothiazine sulphoxide, phenothiazin-3-one, and 3-hydroxyphenothiazine and oxidized phenoxazine to phenoxazin-3-one. 3. Three of the four compounds produced by C. elegans from phenothiazine were identical to those produced by mammals, supporting the use of the fungus as a microbial model for drug metabolism.

The fungus Pestalotiopsis guepini as a model for biotransformation of ciprofloxacin and norfloxacin

The metabolism of the fluoroquinolone drugs ciprofloxacin and norfloxacin by Pestalotiopsis guepini strain P-8 was investigated. Cultures were grown at 28 degrees C in sucrose/peptone broth for 18 days after dosing with ciprofloxacin (300 microM) or norfloxacin (313 microM). Four major metabolites were produced from each drug; and these were purified by high-performance liquid chromatography and identified by mass spectrometry and proton nuclear magnetic resonance spectroscopy. Ciprofloxacin metabolites included N-acetylciprofloxacin (52.0%), desethylene-N-acetylciprofloxacin (9.2%), N-formylciprofloxacin (4.2%), and 7-amino-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (2.3%). Norfloxacin metabolites included N-acetylnorfloxacin (55.4%), desethylene-N-acetylnorfloxacin (8.8%), N-formylnorfloxacin (3.6%), and 7-amino-1-ethyl-6-fluoro4-oxo-1,4-dihydroquinoline-3-carboxylic acid (2.1%). N-Formylciprofloxacin and the four transformation products from norfloxacin are all known to be mammalian metabolites.

Biotransformation of vinclozolin by the fungus Cunninghamella elegans

This study investigated the biotransformation of the dicarboximide fungicide vinclozolin [3-(3,5-dichlorophenyl)-5-methyl-5-vinyl-1,3-oxazolidine-2,4-dione] by the fungus Cunninghamella elegans. Experiments with phenyl-[U-ring-14C]vinclozolin showed that after 96 h incubation, 93% had been transformed to four major metabolites. Metabolites were separated by HPLC and characterized by mass and NMR spectroscopy. Biotransformation occurred predominantly on the oxazolidine-2,4-dione portion of vinclozolin. The metabolites were identified as the 3R- and 3S- isomers of 3',5'-dichloro-2,3,4-trihydroxy-2-methylbutyranilide, N-(2-hydroxy-2-methyl-1-oxobuten-3-yl)-3,5-dichlorophenyl-1-carbamic acid, and 3',5'-dichloro-2-hydroxy-2-methylbut-3-enanilide. The enanilide compound has been reported previously as a plant and mammalian metabolite and is implicated to contain antiandrogenic activity. The 3R- and 3S- isomers of 3',5'-dichloro-2,3,4-trihydroxy-2-methylbutyranilide are novel metabolites.

Evaluation of major active components in St. John's Wort dietary supplements by high-performance liquid chromatography with photodiode array detection and electrospray mass spectrometric confirmation

A RP-HPLC method with photodiode array detection and LC-electrospray ionization (ESI) MS confirmation was established for the determination of major active components in St. John's Wort dietary supplement capsules. The samples alternatively were extracted with ethanol-acetone (2:3) using a 55 degrees C water-bath shaker or an ambient temperature ultrasonic bath. Extracts were separated by RP-C18 chromatography using a 95-min water-methanol-acetonitrile-trifluoroacetic acid gradient. The major components were identified by photodiode array detection and then confirmed by LC-ESI-MS. The quantification of components was performed using an internal standard (luteolin). This method may serve as a valuable tool for the quality evaluation of St. John's Wort dietary supplement products.

Transformation of amoxapine by Cunninghamella elegans

We examined Cunninghamella elegans to determine its ability to transform amoxapine, a tricyclic antidepressant belonging to the dibenzoxazepine class of drugs. Approximately 57% of the exogenous amoxapine was metabolized to three metabolites that were isolated by high-performance liquid chromatography and were identified by nuclear magnetic resonance and mass spectrometry as 7-hydroxyamoxapine (48%), N-formyl-7-hydroxyamoxapine (31%), and N-formylamoxapine (21%). 7-Hydroxyamoxapine, a mammalian metabolite with biological activity, now can be produced in milligram quantities for toxicological evaluation.

Metabolism of the ethanolamine-type antihistamine diphenhydramine (Benadryl) by the fungus Cunninghamella elegans

Two strains of the filamentous fungus Cunninghamella elegans (ATCC 9245 and ATCC 36112) were grown in Sabouraud dextrose broth and screened for the ability to metabolize the ethanolamine-type antihistamine diphenhydramine. Based on the amount of parent drug recovered after 7 days incubation, both C. elegans strains metabolized approximately 74% of the diphenhydramine, 58% of this being identified as organic extractable metabolites. The organic extractable metabolites were isolated by reversed-phase high-performance liquid chromatography and identified by analyzing their mass and nuclear magnetic resonance spectra. Desorption chemical ionization mass spectrometry (DCIMS) with deuterated ammonia was used to differentiate possible isobaric diphenhydramine metabolites and to probe the mechanisms of ion formation under ammonia DCIMS conditions. C. elegans transformed diphenhydramine by demethylation, oxidation, and N-acetylation. The major metabolites observed were diphenhydramine-N-oxide (3%), N-desmethyldiphenhydramine (30%), N-acetyldidesmethyldiphenhydramine (13%), and N-acetyl-N-desmethyldiphenhydramine (12%). These compounds are known mammalian metabolites of diphenhydramine and may be useful for further toxicological studies.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometric detection of bacterial biomarker proteins isolated from contaminated water, lettuce and cotton cloth

Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra of bacterial proteins were obtained from water, lettuce and cloth samples contaminated with Shigella flexneri, Escherichia coli, and Aeromonas hydrophila. Spectra were obtained using proteins directly isolated from water (or water used for rinsing samples) without culturing the bacteria. For S. flexneri and E. coli, two marker ions for specific proteins associated with a virulence-related property (acid resistance) were easily detected. For A. hydrophila, ions from two specifically selected marker proteins, as well as ions from the larger group of proteins isolated from pure cultures, all matched spectra from a contaminated water sample, providing strong evidence that A. hydrophila was the bacterial contaminant. Rinse water from contaminated lettuce and cloth samples showed the same marker ions as the contaminated water samples.

Identification of bacterial proteins observed in MALDI TOF mass spectra from whole cells

Characteristic ions in the MALDI TOF mass spectra from bacterial cells have been associated with four known proteins. The proteins, observed both from cells and in filtered cellular suspensions, were isolated by HPLC and identified on the basis of their mass spectra and their partial amino acid sequence, determined using the Edman method (10-15 residues). The acid resistance proteins HdeA and HdeB give rise to ions near m/z 9735 and 9060 in MALDI TOF mass spectra from cells and from extracts of both Escherichia coli 1090 and Shigella flexneri PHS-1059. However, the proteins associated with proteolytic cleavage by the peptidase Lep, rather than the precursor proteins, were observed, both using cells and from cellular extracts. A cold-shock protein, CspA, was associated with the ion near m/z 7643 from Pseudomonas aeruginosa. Similarly, a cold-acclimation protein, CapB, was identified as the source of the ion near m/z 7684 in P. putida. This last protein was homologous with a known CapB from P. fragi. While these experiments involved the detection of known or homologous proteins from typical bacteria, this same approach could also be applied to the detection of unique proteins or biomarker proteins associated with other bacteria of public health significance.

Comparison of phenanthrene and pyrene degradation by different wood-decaying fungi

The degradation of phenanthrene and pyrene was investigated by using five different wood-decaying fungi. After 63 days of incubation in liquid culture, 13.8 and 4.3% of the [ring U-14C]phenantherene and 2.4 and 1.4% of the [4,5,9,10-14C]pyrene were mineralized by Trametes versicolor and Kuehneromyces mutabilis, respectively. No 14CO2 evolution was detected in either [14C]phenanthrene or [14C]pyrene liquid cultures of Flammulina velutipes, Laetiporus sulphureus, and Agrocybe aegerita. Cultivation in straw cultures demonstrated that, in addition to T. versicolor (15.5%) and K. mutabilis (5.0%), L. sulphureus (10.7%) and A. aegerita (3.7%) were also capable of mineralizing phenanthrene in a period of 63 days. Additionally, K. mutabilis (6.7%), L. sulphureus (4.3%), and A. aegerita (3.3%) mineralized [14C]pyrene in straw cultures. The highest mineralization of [14C] pyrene was detected in straw cultures of T. versicolor (34.1%), which suggested that mineralization of both compounds by fungi may be independent of the number of aromatic rings. Phenanthrene and pyrene metabolites were purified by high-performance liquid chromatography and identified by UV absorption, mass, and 1H nuclear magnetic resonance spectrometry. Fungi capable of mineralizing phenanthrene and pyrene in liquid culture produced enriched metabolites substituted in the K region (C-9,10 position of phenanthrene and C-4,5 position of pyrene), whereas all other fungi investigated produced metabolites substituted in the C-1,2, C-3,4, and C-9,10 positions of phenanthrene and the C-1 position of pyrene.

Reduction of malachite green to leucomalachite green by intestinal bacteria

Intestinal microfloras from human, rat, mouse, and monkey fecal samples and 14 pure cultures of anaerobic bacteria representative of those found in the human gastrointestinal tract metabolized the triphenylmethane dye malachite green to leucomalachite green. The reduction of malachite green to the leuco derivative suggests that intestinal microflora could play an important role in the metabolic activation of the triphenylmethane dye to a potential carcinogen.

Evidence for the role of 2-hydroxychromene-2-carboxylate isomerase in the degradation of anthracene by Sphingomonas yanoikuyae B1

Sphingomonas yanoikuyae B1 is extremely versatile in its catabolic ability. An insertional mutant strain, S. yamoikuyae EK504, which is unable to grow on naphthalene due to the loss of 2-hydroxychromene-2-carboxylate isomerase activity, was utilized to investigate the role of this enzyme in the degradation of anthracene by S. yanoikuyae B1. Although EK504 is unable to grow on anthracene, this strain could transform anthracene to some extent. A metabolite in the degradation of anthracene by EK504 was isolated by high-pressure liquid chromatography (HPLC) and was identified as 6,7-benzocoumarin by UV-visible, gas-chromatographic, HPLC/mass-spectrometric, and 1H nuclear magnetic resonance spectral techniques. The identification of 6,7-benzocoumarin provides direct chemical and genetic evidence for the involvement of nahD in the degradation of anthracene by S. yanoikuyae B1.

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.

Fungal transformations of antihistamines: metabolism of cyproheptadine hydrochloride by Cunninghamella elegans

1. Metabolites formed during incubation of the antihistamine cyproheptadine hydrochloride with the zygomycete fungus Cunninghamella elegans in liquid culture were determined. The metabolites were isolated by hple and identified by mass spectrometric and proton nmr spectroscopic analysis. Two C elegans strains, ATCC 9245 and ATCC 36112, were screened and both produced essentially identical metabolites. 2. Within 72 h cyproheptadine was extensively biotransformed to at least eight oxidative phase-I metabolites primarily via aromatic hydroxylation metabolic pathways. Cyproheptadine was biotransformed predominantly to 2-hydroxycyproheptadine. Other metabolites identified were 1- and 3-hydroxycyproheptadine, cyproheptadine 10,11-epoxide, N-desmethylcyproheptadine, N-desmethyl-2-hydroxycyproheptadine, cyproheptadine N-oxide, and 2-hydroxycyproheptadine N-oxide. Although a minor fungal metabolite, cyproheptadine 10,11-epoxide represents the first stable epoxide isolated from the microbial biotransformation of drugs. 3. The enzymatic mechanism for the formation of the major fungal metabolite, 2-hydroxycyproheptadine, was investigated. The oxygen atom was derived from molecular oxygen as determined from 18O-labelling experiments. The formation of 2-hydroxycyproheptadine was inhibited 35, 70 and 97% by cytochrome P450 inhibitors metyrapone, proadifen and 1-aminobenzotriazole respectively. Cytochrome P450 was detected in the microsomal fractions of C. elegans. In addition, 2-hydroxylase activity was found in cell-free extracts of C. elegans. This activity was inhibited by proadifen and CO, and was inducible by naphthalene. These results are consistent with the fungal epoxidation and hydroxylation reactions being catalysed by cytochrome P450 monooxygenases. 4. The effects of types of media on the biotransformation of cyproheptadine were investigated. It appears that the glucose level significantly affects the biotransformation rates of cyproheptadine; however it did not change the relative ratios between metabolites produced.

Fungal biotransformation of the antihistamine azatadine by Cunninghamella elegans

The metabolism of the antihistamine azatadine by the zygomycete fungus Cunninghamella elegans ATCC 9245 was investigated. Within 72 h from the addition of the drug to 48-h-old cultures grown in Sabouraud dextrose broth, 95% of azatadine was biotransformed. Two major metabolites, 7-hydroxyazatadine (25%) and 8-hydroxyazatadine (50%), and two minor metabolites, N-desmethylazatadine and 9-hydroxyazatadine, were isolated by high-performance liquid chromatography and characterized by mass spectrometric and proton nuclear magnetic resonance spectroscopic analyses.

Fungal metabolism of 2-nitrofluorene

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are direct-acting mutagens and carcinogens that are considered a risk to human health. We investigated the metabolism of 2-nitrofluorene by the fungus Cunninghamella elegans ATCC 36112. At 144 h of incubation, C. elegans had metabolized about 81% of the [9-14C]-2-nitrofluorene, resulting in 6 metabolites. The major metabolites were separated by reversed-phase high-performance liquid chromatography and identified by 1H NMR, ultraviolet (UV)-visible, and mass spectral analyses as 2-nitro-9-fluorenol, 2-nitro-9-fluorenone, 6-hydroxy-2-nitrofluorene, and sulfate conjugates of 7-hydroxy-2-nitro-9-fluorenone and 7-hydroxy-2-nitrofluorene. 2-Nitro-9-fluorenol accounted for about 62% of the total metabolism. For comparison with the microbial system, experiments with liver microsomes of rats pretreated with 3-methyl-cholanthrene were conducted. Microsomal incubations indicated formation of phenolic and ring-hydroxylated products of 2-nitrofluorene. 2-Nitrofluorene and hydroxylated metabolites have been previously implicated as direct-acting mutagens in bacterial assays and have shown sister chromatid exchanges in vivo in bone marrow cells and in vitro in ovary cells and unscheduled DNA synthesis in mammalian studies. Previous studies with other PAHs using C. elegans have shown that the phenols and glucoside and sulfate conjugates of phenols are generally less mutagenic than the parent. The results from the metabolism of 2-nitrofluorene by C. elegans suggests the detoxification potential of this fungus.

Initial oxidative and subsequent conjugative metabolites produced during the metabolism of phenanthrene by fungi

Three filamentous fungi were examined for the ability to biotransform phenanthrene to oxidative (phase I) and conjugative (phase II) metabolites. Phenanthrene metabolites were purified by high-performance liquid chromatography (HPLC) and identified by UV/visible absorption, mass, and 1H NMR spectra. Aspergillus niger ATCC 6275, Syncephalastrum racemosum UT-70, and Cunninghamella elegans ATCC 9245 initially transformed [9-(14)C]phenanthrene to produce metabolites at the 9,10-, 1,2-, and 3,4-positions. Subsequently, sulfate conjugates of phase I metabolites were formed by A. niger, S. racemosum, and C. elegans. Minor glucuronide conjugates of 9-phenanthrol and phenanthrene trans-9, 10-dihydrodiol were formed by S. racemosum and A. niger, respectively. In addition, C. elegans produced the glucose conjugates 1-phenanthryl beta-D-glucopyranoside and 2-hydroxy-1-phenanthryl beta-D-glucopyranoside, a novel metabolite. [9-(14)C]Phenanthrene metabolites were not detected in organic extracts from biotransformation experiments with the yeasts, Candida lipolytica 37-1, Candida tropicalis ATCC 32113, and Candida maltosa R-42.

Mouse liver microsomal metabolism of chloral hydrate, trichloroacetic acid, and trichloroethanol leading to induction of lipid peroxidation via a free radical mechanism

Metabolism of chloral hydrate (CH) by male B6C3F1 mouse liver microsomes (control-microsomes) generated free radical intermediates that resulted in endogenous lipid peroxidation, forming malondialdehyde (MDA), formaldehyde (FA), acetaldehyde (ACT), acetone, and propionaldehyde. Because MDA, FA, and ACT are tumorigens, endogenous formation of lipid peroxidation products via a free radical mechanism may be responsible for hepatocellular tumorigenicity of CH to the B6C3F1 mice. Trichloroacetic acid (TCA) and trichloroethanol (TCE), the primary metabolites of CH, also generated free radicals and induced lipid peroxidation. Lipid peroxidation from TCA equaled that induced by CH, whereas that from TCE was 3- to 4-fold lower, suggesting that metabolism of CH to TCA may be the predominant pathway leading to lipid peroxidation. Metabolism of CH, TCA, and TCE by liver microsomes of mice pretreated with pyrazole (pyrazole-microsomes) yielded lipid peroxidation products at a level 2- to 3-fold higher than those from liver microsomes of untreated mice. In addition, CH-induced lipid peroxidation catalyzed by control-microsomes and pyrazole-microsomes was reduced significantly by 2,4-dichloro-6-phenylphenoxyethylamine, a general cytochrome P450 inhibitor. Thus, our study suggests that cytochrome P450 is the enzyme catalyzing the metabolic activation of CH and its metabolites (TCA and TCE) leading to lipid peroxidation, and that CYP2E1 may be the major isozyme responsible. This latter conclusion was supported by results using human lymphoblastoid cells expressing cytochrome P4502E1, which metabolized CH to reactants inducing mutations, whereas the parental cell line was inactive.

AC corona-discharge aerosol-neutralization device adapted to liquid chromatography/particle beam/mass spectrometry

An AC corona-discharge device was inserted upstream of a thermospray vaporizer tip in a liquid chromatography/particle beam mass spectrometer to neutralize static aerosol charging. Response of a test analyte was measured with or without discharge initiation. If the solvent contained no ammonium acetate buffer, increased analyte signal was associated with the discharge. However, in the presence of ammonium acetate the benefit of AC discharge neutralization was either not observed or was more subtle. This led to the conclusion that the previously observed ammonium acetate "carrier" effect is attributable, at least in part, to neutralization of static electric charges produced spontaneously during the solvent nebulization process. In a second experiment, the pattern of particles issuing from the system momentum separator was examined by aiming the particle beam at a cold target located within a mass spectrometer ion source. Variations in particle density were observed depending on (i) whether or not the aerosol had been neutralized and (ii) the proximity of electron-beam-collimating magnets to the particle beam trajectory. These results are consistent with a hypothesis that electrostatic charging occurs spontaneously during the nebulization process in which an aerosol is formed from the high performance liquid chromatography effluent. Such electrostatic charging introduces a factor likely to degrade system performance by at least two modes: through interactions of the charged aerosol particles (i) with the walls of the aerosol transmission pathway, and, after they are accelerated into a particle beam and introduced into the mass spectrometer, (ii) with the magnets used for electron beam collimation in many mass spectrometer ion sources.

Metabolism of 7-nitrobenz[a]anthracene by intestinal microflora

Pure cultures of anaerobic intestinal bacteria and mixed fecal microflora from human, rat, mouse, and pig were screened for the ability to metabolize 7-nitrobenz[a]anthracene (7-NO2BA). Based on analysis by high-performance liquid chromatography (HPLC) and by ultraviolet (UV), mass, and nuclear magnetic resonance (NMR) spectral techniques, the compounds were identified as 7-aminobenz[a]anthracene (7-NH2BA) and benz[a]anthracene 7,12-dione (dione). Identification of 7-NH2BA as a metabolite of 7-NO2BA indicates that the anaerobic intestinal bacteria are capable of reducing 7-NO2BA to potentially bioactive intermediates. The reductive capacities of the mixed intestinal microflora were generally greater than those of pure cultures. Thus, metabolism of 7-NO2BA in the intestinal tract may be underestimated if pure cultures are used as the sole method for evaluating the potential hazard.

Fungal metabolism of 3-nitrofluoranthene

We investigated the metabolism of 3-nitrofluoranthene by filamentous fungus, Cunninghamella elegans ATCC 36112. Cunninghamella elegans metabolized about 72% of the 3-nitro[3,4-14C]fluoranthene added during 144 h of incubation to 2 major metabolites. These metabolites were separated by reversed-phase high-performance liquid chromatography and identified as 3-nitrofluoranthene-8-sulfate and 3-nitrofluoranthene-9-sulfate by 1H nuclear magnetic resonance, UV-visible, and mass spectral techniques. These results, in conjunction with previous studies on the fungal metabolism of fluoranthene, indicate that the nitro substituent at the C-3 position of fluoranthene sterically hinders epoxidation and shifts metabolism to the C-8 and C-9 positions. Since the phenolic microsomal metabolites of 3-nitrofluoranthene are mutagenic, the formation of sulfate conjugates of 8- and 9-hydroxy-3-nitrofluoranthene by C. elegans suggests that the fungal metabolic pathways may be beneficial for detoxification of this ubiquitous pollutant.

Metabolism of benzonitrile and butyronitrile by Klebsiella pneumoniae

A strain of Klebsiella pneumoniae that used aliphatic nitriles as the sole source of nitrogen was adapted to benzonitrile as the sole source of carbon and nitrogen. Gas chromatographic and mass spectral analyses of culture filtrates indicated that K. pneumoniae metabolized 8.4 mM benzonitrile to 4.0 mM benzoic acid and 2.7 mM ammonia. In addition, butyronitrile was metabolized to butyramide and ammonia. The isolate also degraded mixtures of benzonitrile and aliphatic nitriles. Cell extracts contained nitrile hydratase and amidase activities. The enzyme activities were higher with butyronitrile and butyramide than with benzonitrile and benzamide, and amidase activities were twofold higher than nitrile hydratase activities. K. pneumoniae appears promising for the bioremediation of sites contaminated with aliphatic and aromatic nitriles.

Metabolism of acrylonitrile by Klebsiella pneumoniae

A gram-negative rod-shaped bacterium capable of utilizing acrylonitrile as the sole source of nitrogen was isolated from industrial sewage and identified as Klebsiella pneumoniae. The isolate was capable of utilizing aliphatic nitriles containing 1 to 5 carbon atoms or benzonitrile as the sole source of nitrogen and either acetamide or propionamide as the sole source of both carbon and nitrogen. Gas chromatographic and mass spectral analyses of culture filtrates indicated that K. pneumoniae was capable of hydrolyzing 6.15 mmol of acrylonitrile to 5.15 mmol of acrylamide within 24 h. The acrylamide was hydrolyzed to 1.0 mmol of acrylic acid within 72 h. Another metabolite of acrylonitrile metabolism was ammonia, which reached a maximum concentration of 3.69 mM within 48 h. Nitrile hydratase and amidase, the two hydrolytic enzymes responsible for the sequential metabolism of nitrile compounds, were induced by acrylonitrile. The optimum temperature for nitrile hydratase activity was 55 degrees C and that for amidase was 40 degrees C; both enzymes had pH optima of 8.0.