Degradation of morpholine by an environmental Mycobacterium strain involves a cytochrome P-450

Toxicokinetic and mass balance of morpholine in rats

Morpholine (MOR) has a broad spectrum of use and represents high risk of human exposure. Ingested MOR can undergo endogenous N-nitrosation in the presence of nitrosating agents forming N-nitrosomorpholine (NMOR), classified as possible human carcinogen by the International Agency for Research on Cancer.In this study, we evaluated the MOR toxicokinetics in six groups of male Sprague-Dawley rats orally exposed to 14C-radiolabelled MOR and NaNO2. The major urinary metabolite of MOR, N-nitrosohydroxyethylglycine (NHEG), was measured through HPLC as an index of endogenous N-nitrosation. Mass balance and toxicokinetic profile of MOR were determined by measuring radioactivity in blood/plasma and excreta.MOR reached maximum blood concentration 30 minutes after administration. Elimination rate was rapid (70% in 8h). Most of the radioactivity was excreted in the urine (80.9 ± 0.5%) and unchanged 14C-MOR was the main compound excreted in the urine (84% of the dose recovered). 5.8% of MOR is not absorbed and/or was not recovered.Endogenous nitrosation of MOR was demonstrated by the detection of NHEG. The maximum conversion rate found was 13.3 ± 1.2% and seems to be impacted by the MOR/NaNO2 ratio.These results help refining our knowledge of the endogenous production of NMOR, a possible human carcinogen.

The effect of C/N ratio and its frequent addition on commensal and pathogenic bacterial abundances in shrimp Litopeaneus vanname gut in a biofloc system: Ratio and frequent addition interaction matters

The environmental biotic and abiotic factors form a complicated relationship with the host intestinal microbiota. In our study, we applied different levels of C/N ratio (10, 15, 20) and frequent addition times (once, twice, triple a day) in a factorial experimental design. GC/LC analysis of filtrated biofloc (BF) samples revealed the highest relative fold change for the untargeted bioactive molecules among different treatments, whereas the 16s rRNA analysis revealed the change in the shrimp gut microbiota composition. Based on the available literature on the relationship between the bioactive molecules and the available bacteria in this study, the next bioactive molecules were discussed. Proline was associated with Bacteroidota, Flavobacteriaceae, Gammaproteobacteria, and Flavobacteriales. Plumbagine was associated with Norcardiaceae. Phytosphingosin was associated with Bacteroidota. Phosphocholine compound was associated with Bacteroidota. The monobutyl ether, benzofuran, and piperidone were associated with Micobacteriaceae and Mycobacterium. Generally, C/N 15 and 20 once a day, and C/N 20 triple a day have showed a merit over other treatments in term of low pathogenic and unfavorable bacteria, and high commensal bacterial abundances. The revealed bioactive molecule composition showed the complicity of BF as a source for novel compounds as biosecurity agents in BF system. These molecules could be developed to feed additives upgrading the biosecurity level in aquaculture systems. Other bioactive molecules require future studies to reveal novel molecules in term of aquaculture biosecurity control.

Biological oxidation methods for the removal of organic and inorganic contaminants from wastewater: A comprehensive review

Enzyme-based bioremediation is a simple, cost-effective, and environmentally friendly method for isolating and removing a wide range of environmental pollutants. This study is a comprehensive review of recent studies on the oxidation of pollutants by biological oxidation methods, performed individually or in combination with other methods. The main bio-oxidants capable of removing all types of pollutants, such as organic and inorganic molecules, from fungi, bacteria, algae, and plants, and different types of enzymes, as well as the removal mechanisms, were investigated. The use of mediators and modification methods to improve the performance of microorganisms and their resistance under harsh real wastewater conditions was discussed, and numerous case studies were presented and compared. The advantages and disadvantages of conventional and novel immobilization methods, and the development of enzyme engineering to adjust the content and properties of the desired enzymes, were also explained. The optimal operating parameters such as temperature and pH, which usually lead to the best performance, were presented. A detailed overview of the different combination processes was also given, including bio-oxidation in coincident or consecutive combination with adsorption, advanced oxidation processes, and membrane separation. One of the most important issues that this study has addressed is the removal of both organic and inorganic contaminants, taking into account the actual wastewaters and the economic aspect.

Non-Tuberculous Mycobacteria: Molecular and Physiological Bases of Virulence and Adaptation to Ecological Niches

Non-tuberculous mycobacteria (NTM) are paradigmatic colonizers of the total environment, circulating at the interfaces of the atmosphere, lithosphere, hydrosphere, biosphere, and anthroposphere. Their striking adaptive ecology on the interconnection of multiple spheres results from the combination of several biological features related to their exclusive hydrophobic and lipid-rich impermeable cell wall, transcriptional regulation signatures, biofilm phenotype, and symbiosis with protozoa. This unique blend of traits is reviewed in this work, with highlights to the prodigious plasticity and persistence hallmarks of NTM in a wide diversity of environments, from extreme natural milieus to microniches in the human body. Knowledge on the taxonomy, evolution, and functional diversity of NTM is updated, as well as the molecular and physiological bases for environmental adaptation, tolerance to xenobiotics, and infection biology in the human and non-human host. The complex interplay between individual, species-specific and ecological niche traits contributing to NTM resilience across ecosystems are also explored. This work hinges current understandings of NTM, approaching their biology and heterogeneity from several angles and reinforcing the complexity of these microorganisms often associated with a multiplicity of diseases, including pulmonary, soft-tissue, or milliary. In addition to emphasizing the cornerstones of knowledge involving these bacteria, we identify research gaps that need to be addressed, stressing out the need for decision-makers to recognize NTM infection as a public health issue that has to be tackled, especially when considering an increasingly susceptible elderly and immunocompromised population in developed countries, as well as in low- or middle-income countries, where NTM infections are still highly misdiagnosed and neglected.

Mycobacterial species and their contribution to cholesterol degradation in wastewater treatment plants

Mycobacterium often presents as an abundant bacterial genus in activated sludge in many wastewater treatment plants (WWTPs), but the species-level taxonomy and functions remain poorly understood. In this study, we profiled the mycobacterial communities in eleven WWTPs from five countries by pyrosequencing the rpoB amplicons and searching against a customized database of mycobacterial rpoB sequences. Results indicated that major mycobacterial species were related to M. brumae, M. crocinum, M. sphagni, etc., most of which belong to poorly characterized rapidly-growing group. A few opportunistic pathogenic species were detected, suggesting the potential risk of mycobacteria in WWTPs. Genomic analysis of four isolates from activated sludge indicated these genomes contained genes of degradations of alkane, aromatics, steroids and a variety of cytochrome P450 families. Additionally, a few key genes responsible for cholesterol degradation were detected in a full-scale activated sludge metatranscriptomic dataset reported previously and taxonomically assigned to mycobacteria. Evidence showed that all isolates can degrade cholesterol, a major composition of sewage. Relative abundance of mycobacteria in activated sludge was enriched by 4.7 folds after adding cholesterol into the influent for one week. Our results provided the insights into mycobacterial species and functions in WWTPs.

CATALOGIC 301C model - validation and improvement

In Europe, REACH legislation encourages the use of alternative in silico methods such as (Q)SAR models. According to the recent progress of Chemical Substances Control Law (CSCL) in Japan, (Q)SAR predictions are also utilized as supporting evidence for the assessment of bioaccumulation potential of chemicals along with read across. Currently, the effective use of read across and QSARs is examined for other hazards, including biodegradability. This paper describes the results of external validation and improvement of CATALOGIC 301C model based on more than 1000 tested new chemical substances of the publication schedule under CSCL. CATALOGIC 301C model meets all REACH requirements to be used for biodegradability assessment. The model formalism built on scientific understanding for the microbial degradation of chemicals has a well-defined and transparent applicability domain. The model predictions are adequate for the evaluation of the ready degradability of chemicals.

Biodegradation of corrosion inhibitors and their influence on petroleum product pipeline

The present study enlightens the role of Bacillus cereus ACE4 on biodegradation of commercial corrosion inhibitors (CCI) and the corrosion process on API 5LX steel. Bacillus cereus ACE4, a dominant facultative aerobic species was identified by 16S rDNA sequence analysis, which was isolated from the corrosion products of refined diesel-transporting pipeline in North West India. The effect of CCI on the growth of bacterium and its corrosion inhibition efficiency were investigated. Corrosion inhibition efficiency was studied by rotating cage test and the nature of biodegradation of corrosion inhibitors was also analyzed. This isolate has the capacity to degrade the aromatic and aliphatic hydrocarbon present in the corrosion inhibitors. The degraded products of corrosion inhibitors and bacterial activity determine the electrochemical behavior of API 5LX steel.

Biochemical interpretation of quantitative structure-activity relationships (QSAR) for biodegradation of N-heterocycles: a complementary approach to predict biodegradability

Prediction of the biodegradability of organic compounds is an ecologically desirable and economically feasible tool for estimating the environmental fate of chemicals. We combined quantitative structure-activity relationships (QSAR) with the systematic collection of biochemical knowledge to establish rules for the prediction of aerobic biodegradation of N-heterocycles. Validated biodegradation data of 194 N-heterocyclic compounds were analyzed using the MULTICASE-method which delivered two QSAR models based on 17 activating (OSAR 1) and on 16 inactivating molecular fragments (GSAR 2), which were statistically significantly linked to efficient or poor biodegradability, respectively. The percentages of correct classifications were over 99% for both models, and cross-validation resulted in 67.9% (GSAR 1) and 70.4% (OSAR 2) correct predictions. Biochemical interpretation of the activating and inactivating characteristics of the molecular fragments delivered plausible mechanistic interpretations and enabled us to establish the following biodegradation rules: (1) Target sites for amidohydrolases and for cytochrome P450 monooxygenases enhance biodegradation of nonaromatic N-heterocycles. (2) Target sites for molybdenum hydroxylases enhance biodegradation of aromatic N-heterocycles. (3) Target sites for hydratation by an urocanase-like mechanism enhance biodegradation of imidazoles. Our complementary approach represents a feasible strategy for generating concrete rules for the prediction of biodegradability of organic compounds.

Influence of an oil soluble inhibitor on microbiologically influenced corrosion in a diesel transporting pipeline

Microbial degradation of the oil soluble corrosion inhibitor (OSCI) Baker NC 351 contributed to a decrease in inhibitor efficiency. Corrosion inhibition efficiency was studied by the rotating cage and flow loop methods. The nature of the biodegradation of the corrosion inhibitor was also analysed using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry. The influence of bacterial activity on the degradation of the corrosion inhibitor and its influence on corrosion of API 5LX were evaluated using a weight loss technique and impedance studies. Serratia marcescens ACE2 and Bacillus cereus ACE4 can degrade aromatic and aliphatic hydrocarbons present in the corrosion inhibitor. The present study also discusses the demerits of the oil soluble corrosion inhibitors used in petroleum product pipeline.

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.

Water-soluble inhibitor on microbiologically influenced corrosion in diesel pipeline

The effect of water-soluble corrosion inhibitor on the growth of bacteria and its corrosion inhibition efficiency were investigated. Corrosion inhibition efficiency was studied by rotating cage test and flow loop techniques. The nature of biodegradation of corrosion inhibitor was also analyzed by using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR) and Gas chromatography and mass spectrometer (GC-MS). The bacterial isolates (Serratia marcescens ACE2, Bacillus cereus ACE4) have the capacity to degrade the aromatic and aliphatic hydrocarbon present in the corrosion inhibitor. The degraded products of corrosion inhibitor and bacterial activity determine the electrochemical behaviour of API 5LX steel. The influence of bacterial activity on degradation of corrosion inhibitor and its influence on corrosion of API 5LX have been evaluated by employing weight loss techniques and electrochemical studies. The main finding of this paper is that the water-soluble corrosion inhibitor is consumed by the microbial action, which contributes to the decrease in inhibitor efficiency. The present study also emphasis the importance of evaluation of water-soluble corrosion inhibitor in stagnant model (flow loop test) and discusses the demerits of the water-soluble corrosion inhibitors in petroleum product pipeline.

Degradation of 2,5-dimethylpyrazine by Rhodococcus erythropolis strain DP-45 isolated from a waste gas treatment plant of a fishmeal processing company

A bacterium, strain DP-45, capable of degrading 2,5-dimethylpyrazine (2,5-DMP) was isolated and identified as Rhodococcus erythropolis. The strain also grew on many other pyrazines found in the waste gases of food industries, like 2,3-dimethylpyrazine (2,3-DMP), 2,6-dimethylpyrazine (2,6-DMP), 2-ethyl-5(6)-dimethylpyrazine (EMP), 2-ethylpyrazine (EP), 2-methylpyrazine (MP), and 2,3,5-trimethylpyrazine (TMP). The strain utilized 2,5-DMP as sole source of carbon and nitrogen and grew optimally at 25 degrees C with a doubling time of 7.6 h. The degradation of 2,5-DMP was accompanied by the growth of the strain and by the accumulation of a first intermediate, identified as 2-hydroxy-3,6-dimethylpyrazine (HDMP). The disappearance of HDMP was accompanied by the release of ammonium into the medium. No other metabolite was detected. The degradation of 2,5-DMP and HDMP by strain DP-45 required molecular oxygen. The expression of the first enzyme in the pathway was induced by 2,5-DMP and HDMP whereas the second enzyme was constitutively expressed. The activity of the first enzyme was inhibited by diphenyliodonium (DPI), a flavoprotein inhibitor, methimazole, a competitive inhibitor of flavin-containing monooxygenases, and by cytochrome P450 inhibitors, 1-aminobenzotriazole (ABT) and phenylhydrazine (PHZ). The activity of the second enzyme was inhibited by DPI, ABT, and PHZ. Sodium tungstate, a specific antagonist of molybdate, had no influence on growth and consumption of 2,5-DMP by strain DP-45. These results led us to propose that a flavin-dependent monooxygenase or a cytochrome P450-dependent monooxygenase rather than a molybdenum hydroxylase catalyzed the initial hydroxylation step and that a cytochrome P450 enzyme is responsible for the transformation of HDMP in the second step.

Physiological, biochemical, and genetic characterization of an alicyclic amine-degrading Mycobacterium sp. strain THO100 isolated from a morpholine-containing culture of activated sewage sludge

Mycobacterium sp. strain THO100 was isolated from a morpholine-containing culture of activated sewage sludge. This strain was able to utilize pyrrolidine, morpholine, piperidine, piperazine, and 1,2,3,6-tetrahydropyridine as the sole sources of carbon, nitrogen, and energy. The degradation pathway of pyrrolidine as the best substrate for cellular growth was proposed based on the assays of substrate-induced cytochrome P450 and constitutive enzyme activities toward 4-aminobutyric acid (GABA) and succinic semialdehyde (SSA). Its 16S ribosomal RNA gene sequence (16S rDNA) was identical to that of Mycobacterium tokaiense ATCC 27282(T). The morABC genes responsible for alicyclic amine degradation were nearly identical among different species of Mycobacteria. Remarkably, repetitive sequences at the intergenic spacer (IGS) region between morC and orf1' were detected by comparison of the nearly identical mor gene cluster regions. Considering the strain activity for alicyclic amine degradation, the deleted 65-bp DNA segment did not significantly alter the open reading frames, and the expression and functions of the P450(mor) system remained unaltered. In addition, we found a spontaneous deletion of P450(mor) from another strain HE5 containing the archetypal mor gene cluster, which indicated a possible occurrence of DNA recombination to rearrange the DNA.

Rhodococcus sp. strain TM1 plays a synergistic role in the degradation of piperidine by Mycobacterium sp. strain THO100

Mycobacterium sp. strain THO100 and Rhodococcus sp. strain TM1 were isolated from a morpholine-containing enrichment culture of activated sewage sludge. Strain THO100, but not strain TM1, was able to degrade alicyclic amines such as morpholine, piperidine, and pyrrolidine. The mixed strains THO100 and TM1 showed a better growth on piperidine as the substrate than the pure strain THO100 because strain TM1 was able to reduce the level of glutaraldehyde (GA) produced during piperidine degradation. GA was toxic to strain THO100 (IC(50) = 28.3 microM) but less toxic to strain TM1 (IC(50) = 215 microM). Strain THO100 possessed constitutive semialdehyde dehydrogenases, namely Sad1 and Sad2, whose activities toward succinic semialdehyde (SSA) were strongly inhibited by GA. The two isozymes were identified as catalase-peroxidase (KatG = Sad1) and semialdehyde dehydrogenase (Sad2) based on mass spectrometric analyses of tryptic peptides and database searches of the partial DNA sequences of their genes. In contrast, strain TM1 containing another constitutive enzyme Gad1 could oxidize both SSA and GA. This study suggested that strain TM1 possessing Gad1 played a synergistic role in reducing the toxic and inhibitory effects of GA produced in the degradation of piperidine by strain THO100.

Degradation of 2,3-diethyl-5-methylpyrazine by a newly discovered bacterium, Mycobacterium sp. strain DM-11

A bacterium was isolated from the waste gas treatment plant at a fishmeal processing company on the basis of its capacity to use 2,3-diethyl-5-methylpyrazine (DM) as a sole carbon and energy source. The strain, designated strain DM-11, grew optimally at 25 degrees C and had a doubling time of 29.2 h. The strain did not grow on complex media like tryptic soy broth, Luria-Bertani broth, or nutrient broth or on simple carbon sources like glucose, acetate, oxoglutarate, succinate, or citrate. Only on Löwenstein-Jensen medium was growth observed. The 16S rRNA gene sequence of strain DM-11 showed the highest similarity (96.2%) to Mycobacterium poriferae strain ATCC 35087T. Therefore, strain DM-11 merits recognition as a novel species within the genus Mycobacterium. DM also served as a sole nitrogen source for the growth of strain DM-11. The degradation of DM by strain DM-11 requires molecular oxygen. The first intermediate was identified as 5,6-diethyl-2-hydroxy-3-methylpyrazine (DHM). Its disappearance was accompanied by the release of ammonium into the culture medium. No other metabolite was detected. We conclude that ring fission occurred directly after the formation of DHM and ammonium was eliminated after ring cleavage. Molecular oxygen was essential for the degradation of DHM. The expression of enzymes involved in the degradation of DM and DHM was regulated. Only cells induced by DM or DHM converted these compounds. Strain DM-11 also grew on 2-ethyl-5(6)-methylpyrazine (EMP) and 2,3,5-trimethylpyrazine (TMP) as a sole carbon, nitrogen, and energy source. In addition, the strain converted many pyrazines found in the waste gases of food industries cometabolically.

Analysis of the nearly identical morpholine monooxygenase-encoding mor genes from different Mycobacterium strains and characterization of the specific NADH : ferredoxin oxidoreductase of this cytochrome P450 system

Cloning and sequencing of the morABC operon region revealed the genes encoding the three components of a cytochrome P450 monooxygenase, which is required for the degradation of the N-heterocycle morpholine by Mycobacterium sp. strain HE5. The cytochrome P450 (P450(mor)) and the Fe(3)S(4) ferredoxin (Fd(mor)), encoded by morA and morB, respectively, have been characterized previously, whereas no evidence has hitherto been obtained for a specifically morpholine-induced reductase, which would be required to support the activity of the P450(mor) system. Analysis of the mor operon has now revealed the gene morC, encoding the ferredoxin reductase of this morpholine monooxygenase. The genes morA, morB and morC were identical to the corresponding genes from Mycobacterium sp. strain RP1. Almost identical mor genes in Mycobacterium chlorophenolicum PCP-1, in addition to an inducible cytochrome P450, pointing to horizontal gene transfer, were now identified. No evidence for a circular or linear plasmid was found in Mycobacterium sp. strain HE5. Analysis of the downstream sequences of morC revealed differences in this gene region between Mycobacterium sp. strain HE5 and Mycobacterium sp. strain RP1 on the one hand, and M. chlorophenolicum on the other hand, indicating insertions or deletions after recombination. Downstream of the mor genes, the gene orf1', encoding a putative glutamine synthetase, was identified in all studied strains. The gene morC of Mycobacterium sp. strain HE5 was heterologously expressed. The purified recombinant protein FdR(mor) was characterized as a monomeric 44 kDa protein, being a strictly NADH-dependent, FAD-containing reductase. The K(m) values of FdR(mor) for the substrate NADH (37.7 +/- 4.1 microM) and the artificial electron acceptors potassium ferricyanide (14.2 +/- 1.1 microM) and cytochrome c (28.0 +/- 3.6 microM) were measured. FdR(mor) was shown to interact functionally with its natural redox partner, the Fe(3)S(4) protein Fd(mor), and with the Fe(2)S(2) protein adrenodoxin, albeit with a much lower efficiency, but not with spinach ferredoxin. In contrast, adrenodoxin reductase, the natural redox partner of adrenodoxin, could not use Fd(mor) in activity assays. These results indicated that FdR(mor) can utilize different ferredoxins, but that Fd(mor) requires the specific NADH : ferredoxin oxidoreductase FdR(mor) from the P450(mor) system for efficient catalytic function.

Biodegradation of bisphenol A by cells and cell lysate from Sphingomonas sp. strain AO1

The capacity and pathway of bisphenol A [BPA; 2,2-bis(4-hydroxyphenyl)propane] degradation in Sphingomonas sp. strain AO1, which was isolated from the soil of a vegetable-growing field in Japan, were investigated. The bacterial strain was able to grow in a basal mineral salt medium containing BPA as the sole carbon source (BSMB medium), and was able to degrade 115 microg ml(-1) BPA in 6 h in L medium. Several BPA metabolites were detected in the culture supernatant by HPLC and then identified by GC-MS and LC-MS-MS. These compounds were confirmed to be the same as those reported for other BPA-degrading bacteria. BPA degradation by cells in the basal mineral salt medium was induced by BPA, and activity was detected only in the intracellular soluble fraction in the presence of coenzymes, such as NADH, NAD+, NADPH or NADP+. The addition of metyrapone, a cytochrome P450 inhibitor, to BSMB medium resulted in a decrease in BPA degradation and cell growth. The BPA-degradation activity of the intracellular soluble fraction was also inhibited by the cytochrome P450 inhibitor. Carbon monoxide difference spectra indicated that cytochrome P450 was present in the cells and that the amount of cytochrome P450 corresponded to the cellular BPA-degradation activity. Our results provide evidence that the cytochrome P450 system is involved in BPA metabolism in Sphingomonas sp. strain AO1.

Kinetic and binding studies with purified recombinant proteins ferredoxin reductase, ferredoxin and cytochrome P450 comprising the morpholine mono-oxygenase from Mycobacterium sp. strain HE5

The P450mor system from Mycobacterium sp. strain HE5, supposed to catalyse the hydroxylation of different N-heterocycles, is composed of three components: ferredoxin reductase (FdRmor), Fe3S4 ferredoxin (Fdmor) and cytochrome P450 (P450mor). In this study, we purified Fdmor and P450mor as recombinant proteins as well as FdRmor, which has been isolated previously. Kinetic investigations of the redox couple FdRmor/Fdmor revealed a 30-fold preference for the NADH-dependent reduction of nitroblue tetrazolium (NBT) and an absolute requirement for Fdmor in this reaction, compared with the NADH-dependent reduction of cytochrome c. The quite low Km (5.3 +/- 0.3 nm) of FdRmor for Fdmor, measured with NBT as the electron acceptor, indicated high specificity. The addition of sequences providing His-tags to the N- or C-terminus of Fdmor did not significantly alter kinetic parameters, but led to competitive background activities of these fusion proteins. Production of P450mor as an N-terminal His-tag fusion protein enabled the purification of this protein in its spectral active form, which has previously not been possible for wild-type P450mor. The proposed substrates morpholine, piperidine or pyrrolidine failed to produce substrate-binding spectra of P450mor under any conditions. Pyridine, metyrapone and different azole compounds generated type II binding spectra and the Kd values determined for these substances suggested that P450mor might have a preference for more bulky and/or hydrophobic molecules. The purified recombinant proteins FdRmor, Fdmor and P450mor were used to reconstitute the homologous P450-containing mono-oxygenase, which was shown to convert morpholine.

Molecular cloning, nucleotide sequencing and expression of genes encoding a cytochrome P450 system involved in secondary amine utilization in Mycobacterium sp. strain RP1

Mycobacterium sp. strain RP1 degrades morpholine, piperidine, and pyrrolidine and is able to use these compounds as the sole source of carbon, nitrogen, and energy. Cytochrome P450 (MorA) is involved in the biodegradation of these secondary amines. A 3.9-PstI genomic DNA fragment, containing the gene encoding MorA, was cloned and sequenced. Four open reading frames were detected on this DNA fragment. The first encoded a cytochrome P450 designated as MorA which was the second member of the CYP151 family and was named CYP151A2. The second open reading frame (morB) featured a [3Fe-4S] type of ferredoxin. A third gene (morC), exhibiting sequence identity to known reductases, and a fourth truncated gene encoding a putative glutamine reductase (orf1' ), were found downstream of morB. Recombinant MorA cytochrome P450 was purified to homogeneity from Escherichia coli. The purified enzyme was a monomeric soluble protein with an apparent Mr of about 45,000. CYP151A2 catalyzed the ring cleavage of the secondary amines and the Vmax/KMapp values indicated that pyrrolidine is the preferred substrate for this monooxygenase.

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.

Biodegradation of cyclic amines by a Pseudomonas strain involves an amine mono-oxygenase

Pseudomonas putida O1G3 catalyzes the degradation of pyrrolidine and piperidine. This strain can use these compounds as the sole source of carbon, nitrogen, and energy. When the cyclic amines were used as the growth substrates, the synthesis of a soluble heme amine mono-oxygenase was induced in this bacteria. This observation was confirmed by spectrophotometric analysis and specific inhibitor. This mono-oxygenase is a NADH-dependent enzyme and catalyzes the cleavage of the C-N bond of the pyrrolidine and piperidine ring by a mechanism similar to a N dealkylation. This reaction could be followed by ring cleavage to form gamma-aminobutyraldehyde oxidized to gamma-aminobutyrate. Further investigations to purify the heme-containing mono-oxygenase are in progress.

Benzothiazole degradation by Rhodococcus pyridinovorans strain PA: evidence of a catechol 1,2-dioxygenase activity

The pathway for biodegradation of benzothiazole (BT) and 2-hydroxybenzothiazole (OBT) by Rhodococcus pyridinovorans strain PA was studied in detail. The kinetics of biodegradation were monitored by in situ (1)H nuclear magnetic resonance (NMR) in parallel with reversed-phase high-performance liquid chromatography (HPLC). Successive oxidations from BT to OBT and then from OBT to dihydroxybenzothiazole were observed. Further insight was obtained by using a mutant strain with impaired ability to grow on BT and OBT. The precise structure of another intermediate was determined by in situ two-dimensional (1)H-(13)C NMR and HPLC-electrospray ionization mass spectrometry; this intermediate was found to be a ring-opening product (a diacid structure). Detection of this metabolite, together with the results obtained by (1)H and (19)F NMR when cells were incubated with 3-fluorocatechol, demonstrated that a catechol 1,2-dioxygenase is involved in a pathway for biodegradation of BTs in this Rhodococcus strain. Our results show that catechol 1,2-dioxygenase and catechol 2,3-dioxygenase activities may both be involved in the biodegradation of BTs depending on the culture conditions.

Evidence that RDX biodegradation by Rhodococcus strain DN22 is plasmid-borne and involves a cytochrome p-450

AIMS

To investigate the biodegradation of the explosive compound RDX in Rhodococcus strain DN22, a bacterium previously isolated for its ability to grow on RDX as sole nitrogen source.

METHODS AND RESULTS

Analysis of the rates of RDX degradation and nitrite production indicated that 2 mol nitrite were produced per mole RDX degraded. Cells of strain DN22 had the highest activity against RDX during the exponential phase and low activity in the stationary phase. Nitrite production from RDX was inhibited by metyrapone, menadione, piperonyl butoxide, n-octylamine and carbon monoxide and inducible by pyrrolidine, pyridine and atrazine. Acridine orange treatment yielded RDX-minus derivatives of strain DN22 at a curing rate of 1.5% and all of the cured derivatives had lost a large plasmid.

CONCLUSIONS

RDX biodegradation in strain DN22 appears to involve a plasmid-encoded cytochrome p-450 enzyme.

SIGNIFICANCE AND IMPACT OF THE STUDY

Plasmid-borne RDX degradation genes could potentially be transferred between bacteria. Our research into RDX metabolism in strain DN22 will facilitate future applications of this bacterium for bioremediation.

Long-range (1)H-(15)N heteronuclear shift correlation at natural abundance: a tool to study benzothiazole biodegradation by two rhodococcus strains

The biodegradation of benzothiazole and 2-hydroxybenzothiazole by two strains of Rhodococcus was monitored by reversed phase high-pressure liquid chromatography and by (1)H nuclear magnetic resonance (NMR). Both xenobiotics were biotransformed into a hydroxylated derivative of 2-hydroxybenzothiazole by these two strains. The chemical structure of this metabolite was determined by a new NMR methodology: long-range (1)H-(15)N heteronuclear shift correlation without any previous (15)N enrichment of the compound. This powerful NMR tool allowed us to assign the metabolite structure to 2,6-dihydroxybenzothiazole.

Online NMR for monitoring biocatalysed reactions

Monitoring biocatalysed reactions and metabolic pathways using NMR spectroscopy is of growing interest. As a non-invasive analytical method providing simultaneous information about intracellular and extracellular constituents, it is superior to other analytical techniques and has a wide range of applications: kinetics and stoichiometrics of metabolic events, metabolic fluxes and enzyme activities can be detected in situ or after taking a sample from the biotransformation mixture. New NMR pulse sequences provide even more valuable experiments in these fields. Research topics range from the monitoring of polymer formation to fermentations producing beverages or antibiotics. Routine monitoring of industrial fermentations by NMR seems to be imminent.

Common degradative pathways of morpholine, thiomorpholine, and piperidine by Mycobacterium aurum MO1: evidence from (1)H-nuclear magnetic resonance and ionspray mass spectrometry performed directly on the incubation medium

In order to see if the biodegradative pathways for morpholine and thiomorpholine during degradation by Mycobacterium aurum MO1 could be generalized to other heterocyclic compounds, the degradation of piperidine by this strain was investigated by performing (1)H-nuclear magnetic resonance directly with the incubation medium. Ionspray mass spectrometry, performed without purification of the samples, was also used to confirm the structure of some metabolites during morpholine and thiomorpholine degradation. The results obtained with these two techniques suggested a general pathway for degradation of nitrogen heterocyclic compounds by M. aurum MO1. The first step of the degradative pathway is cleavage of the C---N bond; this leads formation of an intermediary amino acid, which is followed by deamination and oxidation of this amino acid into a diacid. Except in the case of thiodiglycolate obtained from thiomorpholine degradation, the dicarboxylates are completely mineralized by the bacterial cells. A comparison with previously published data showed that this pathway could be a general pathway for degradation by other strains of members of the genus Mycobacterium.

High morpholine degradation rates and formation of cytochrome P450 during growth on different cyclic amines by newly isolated Mycobacterium sp. strain HE5

Using morpholine as sole source of carbon, nitrogen and energy, strain HE5 (DSM 44238) was isolated from forest soil. The isolated strain was identified as a member of the subgroup of fast-growing Mycobacterium species as revealed by 16S rDNA analysis. An identity of 99.4% was obtained to Mycobacterium gilvum; however, the type strain was unable to utilize morpholine. A maximal growth rate of 0.17 h(-1) was observed at a morpholine concentration of 30 mM, 30 degrees C and pH 7.2. The substrate was tolerated at concentrations up to 100 mM. Besides morpholine, the strain utilized pyrrolidine, piperidine and proposed intermediates in morpholine metabolism such as glycolate, glyoxylate and ethanolamine. Degradation of morpholine, piperidine and pyrrolidine by resting or permeabilized cells was strictly dependent on the presence of oxygen. Addition of the cytochrome-P450-specific inhibitor metyrapone to the growth medium resulted in a significantly decreased growth rate if these cyclic amines were used as a substrate. Carbon monoxide difference spectra of crude extracts from cells grown on these substrates compared to spectra obtained for extracts of succinate-grown cells indicated that cytochrome P450 is specifically expressed during growth on the cyclic amines. These data indicated that a cytochrome-P450-dependent monooxygenase is involved in the degradation of the three cyclic amines.

Cloning and characterization of the genes encoding a cytochrome P450 (PipA) involved in piperidine and pyrrolidine utilization and its regulatory protein (PipR) in Mycobacterium smegmatis mc2155

Transposon mutagenesis of Mycobacterium smegmatis mc2155 enabled the isolation of a mutant strain (called LGM1) altered in the regulation of piperidine and pyrrolidine utilization. The complete nucleotide sequence of the gene inactivated in mutant LGM1 was determined from the wild-type strain. This gene (pipR) encoded a member of the GntR family of bacterial regulatory proteins. An insertion element (IS1096), previously described for M. smegmatis, was detected downstream of the gene pipR. Three additional open reading frames were found downstream of IS1096. The first open reading frame (pipA) appeared to encode a protein identified as a cytochrome P450 enzyme. This gene is the first member of a new family, CYP151. By a gene replacement experiment, it was demonstrated that the cytochrome P450 pipA gene is required for piperidine and pyrrolidine utilization in M. smegmatis mc2155. Genes homologous to pipA were detected by hybridization in several, previously isolated, morpholine-degrading mycobacterial strains. A gene encoding a putative [3Fe-4S] ferredoxin (orf1) and a truncated gene encoding a putative glutamine synthetase (orf2') were found downstream of pipA.

Degradation of morpholine, piperidine, and pyrrolidine by mycobacteria: evidences for the involvement of a cytochrome P450

Nine bacterial strains that grew on morpholine and pyrrolidine as sole carbon, nitrogen, and energy sources were isolated from three different environments with no known morpholine contamination. One of these strains could also degrade piperidine. These bacteria were identified as Mycobacterium strains. A phylogenetic analysis based on the partial 16S rDNA sequences indicated that the isolated strains clustered within the fast growing group of mycobacteria. When the above-mentioned cyclic amines were used as growth substrates, the synthesis of a soluble cytochrome P450 was induced in all these bacteria. Other laboratory strains, Mycobacterium fortuitum and Mycobacterium smegmatis mc2155, were tested for their abilities to degrade morpholine. Neither of them degraded morpholine but could use pyrrolidine and piperidine. The growth of M. fortuitum and M. smegmatis mc2155 on these compounds involved a soluble cytochrome P450, suggesting that mycobacterial strains are naturally able to use pyrrolidine and have developed a similar enzymatic pathway to metabolize this amine.Key words: mycobacteria, morpholine, piperidine, pyrrolidine, cytochrome P450.

Morpholine degradation pathway of Mycobacterium aurum MO1: direct evidence of intermediates by in situ 1H nuclear magnetic resonance

Resting Mycobacterium aurum MO1 cells were incubated with morpholine, a waste from the chemical industry. The kinetics of biodegradation was monitored by using in situ nuclear magnetic resonance (NMR). The incubation medium was directly analyzed by 1H NMR. This technique allowed the unambiguous identification of two intermediates of the metabolic pathway involved in the biodegradation process, glycolate and 2-(2-aminoethoxy)acetate. The latter compound, which was not commercially available, was synthesized, in three steps, from 2-(2-aminoethoxy)ethanol. Quantitative analysis of the kinetics of degradation of morpholine was performed by integrating the signals of the different metabolites in 1H-NMR spectra. Morpholine was degraded within 10 h. The intermediates increased during the first 10 h and finally disappeared after 20 h incubation. Assays of degradation were also carried out with glycolate and ethanolamine, hypothetical intermediates of the morpholine degradation pathway. They were degraded within 4 and 8 h, respectively. Until now, no tool for direct detection of intermediates or even morpholine has been available, consequently, only hypothetical pathways have been proposed. The approach described here gives both qualitative and quantitative information about the metabolic routes used in morpholine degradation by M. aurum MO1. It could be used to investigate many biodegradative processes.