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PubMed2002

Phylogenetic and metabolic diversity of bacteria degrading aromatic compounds under denitrifying conditions, and description of Thauera phenylacetica sp. nov., Thauera aminoaromaticasp. nov., and Azoarcus buckelii sp. nov.

Six strains of denitrifying bacteria isolated from various oxic and anoxic habitats on different monocyclic aromatic substrates were characterized by sequencing 16S rRNA genes, determining physiological and morphological traits, and DNA-DNA hybridization. According to these criteria, strains S100, SP and LG356 were identified as members of Thauera aromatica. Strains B5-1 and B5-2 were tentatively affiliated to the species Azoarcus tolulyticus. Strains B4P and S2 were only distantly related to each other and to other described Thauera species. These two strains are proposed as the type strains of two new species, Thauera phenylacetica sp. nov. and Thauera aminoaromaticasp. nov., respectively. By 16S rRNA gene analysis, strain U120 was highly related to the type strains of Azoarcus evansii and Azoarcus anaerobius, whereas corresponding DNA-DNA reassociation values indicated only a low degree of genomic relatedness. Based upon a low DNA similarity value and the presence of distinguishing physiological properties, strain U120 is proposed as the type strain of a new species, Azoarcus buckelii sp. nov. Almost all of the new isolates were obtained with different substrates. The highly varied substrate spectra of the isolates indicates that an even higher diversity of denitrifying bacteria degrading aromatic compounds would be discovered in the different habitats by using a larger spectrum of aromatic substrates for enrichment and isolation.

Azoarcus↗
PubMed2004

Adsorption of aromatic compounds from water by treated carbon materials.

Carbon materials with different textural and surface chemistry properties have been studied to analyze their behavior in removing aromatic compounds (phenol, o-chlorophenol, p-nitrophenol, aniline, and phenol compound mixtures) from water. A mesoporous high surface area graphite and a microporous activated carbon with (HSAGox and ACox) and without (HSAGT and ACT) oxygen surface groups, were used as adsorbents. Apparent surface areas, surface oxygen groups, and zero points of charge have been determined. The adsorption behavior of single compounds on ACT depends on the relation between the molecular and the pore sizes. The aniline, the nitrophenol, and the chlorophenol interact with the oxygen surface groups of oxidized graphite, while there is no evidence of any type of interaction of the phenol with these groups. The adsorption of the organic compound mixtures on the thermally treated samples is determined by the acid-base character of the adsorbate-adsorbent, whereas on the oxidized carbons, the controlling forces are the specific interactions between organic molecules and the oxygenated groups. Selectivity coefficients for the different mixtures are presented over the entire range of adsorption.

Adsorption↗
PubMed2005

Characterization of a closed-shell fluorine-fluorine bonding interaction in aromatic compounds on the basis of the electron density.

A bond path linking two saturated fluorine atoms is found to be ubiquitous in crowded difluorinated aromatic compounds. The bond path is shown to persist for a range of internuclear distances (2.3-2.8 A) and a range of relative orientations of the two C-F internuclear axes. The F. . .F bonding is shown to exhibit all the hallmarks of a closed-shell weak interaction. The presence of such a bond path can impart as much as 14 kcal/mol of local stabilization to the molecule in which it exists, a stabilization that can be offset or even overwhelmed by destabilization of other regions in the molecule. Several other weak closed-shell interactions were also found and characterized including F. . .C, F. . .O, and C. . .C interactions, hydrogen bonding, dihydrogen bonding, and hydrogen-hydrogen bonding. This study represents another example of the usefulness and richness of the bond path concept and of the theory of atoms in molecules in general.

Journal Article↗
PubMed1988

Determination of polycyclic aromatic compounds by high-performance liquid chromatography with simultaneous mass spectrometry and ultraviolet diode array detection.

A major problem in the determination of polycyclic aromatic compounds (PACs) in environmental samples is the extreme complexity of the extracts, even after extensive fractionation. The combination of high-performance liquid chromatography (HPLC) with simultaneous mass spectrometry (MS) and ultraviolet diode array detection (DAD) is a powerful tool for the identification and quantitation of such species with a high degree of confidence. HPLC allows the selective separation of a wide variety of PACs, including thermally labile and high molecular weight compounds. Electron ionization MS with the moving belt interface provides high sensitivity and selectivity, as well as structural information such as molecular weight, functional groups, and elemental composition. The diode array detector helps to differentiate isomeric structures and confirm compound identity.

Chromatography, High Pressure Liquid↗
PubMed2000

Positive selection for mutations affecting bioconversion of aromatic compounds in Agrobacterium tumefaciens: analysis of spontaneous mutations in the protocatechuate 3,4-dioxygenase gene.

A positive selection method for mutations affecting bioconversion of aromatic compounds was applied to a mutant strain of Agrobacterium tumefaciens A348. The nucleotide sequence of the A348 pcaHGB genes, which encode protocatechuate 3,4-dioxygenase (PcaHG) and beta-carboxy-cis,cis-muconate cycloisomerase (PcaB) for the first two steps in catabolism of the diphenolic protocatechuate, was determined. An omega element was introduced into the pcaB gene of A348, creating strain ADO2077. In the presence of phenolic compounds that can serve as carbon sources, growth of ADO2077 is inhibited due to accumulation of the tricarboxylate intermediate. The toxic effect, previously described for Acinetobacter sp., affords a powerful selection for suppressor mutations in genes required for upstream catabolic steps. By monitoring loss of the marker in pcaB, it was possible to determine that the formation of deletions was minimal compared to results obtained with Acinetobacter sp. Thus, the tricarboxylic acid trick in and of itself does not appear to select for large deletion mutations. The power of the selection was demonstrated by targeting the pcaHG genes of A. tumefaciens for spontaneous mutation. Sixteen strains carrying putative second-site mutations in pcaH or -G were subjected to sequence analysis. All single-site events, their mutations revealed no particular bias toward multibase deletions or unusual patterns: five (-1) frameshifts, one (+1) frameshift, one tandem duplication of 88 bp, one deletion of 92 bp, one nonsense mutation, and seven missense mutations. PcaHG is considered to be the prototypical ferric intradiol dioxygenase. The missense mutations served to corroborate the significance of active site amino acid residues deduced from crystal structures of PcaHG from Pseudomonas putida and Acinetobacter sp. as well as of residues in other parts of the enzyme.

Agrobacterium tumefaciens↗
PubMed1990

DNA adducts in humans related to occupational and environmental exposure to aromatic compounds.

White blood cell DNA adducts were measured in coke workers, local controls and countryside controls using the 32P-postlabelling technique and immunoassay. The methods detected aromatic adducts, including those formed by polycyclic aromatic hydrocarbons. Coke workers are heavily exposed to aromatic compounds, which are also emitted in large amounts into the environment. The two techniques detected a large difference in adduct levels between the coke workers and the countryside controls. The adduct levels in the local controls were substantially higher than those in the countryside controls. As occupational exposure did not account for such a difference, the data suggest that the source of aromatic adducts in local controls is environmental pollution.

Adult↗
PubMed1997

Improved detection of polycyclic aromatic compounds in complex mixtures by liquid chromatographic fractionation on poly(divinylbenzene) prior to gas chromatography-mass spectrometry. Application to the analysis of diesel particulates.

Polycyclic aromatic compounds (PACs) are preferentially retained over other compound classes during high-performance liquid chromatography (HPLC) on poly(divinylbenzene) (PDVB) columns with a dichloromethane mobile phase. PAC retention during HPLC with PDVB/CH2Cl2 is governed by a multi-mode mechanism that has been previously described. This enhanced retention of PACs makes PDVB columns useful for isolating a PAC fraction from highly complex mixtures such as the emissions from fossil-fuels combustion. The cleaned-up PAC fraction yields a simple chromatogram with easily identified and quantified peaks without significant compound loss or danger of contamination. We illustrate the use of this clean-up method for the isolation of the PAC fraction from a standard reference diesel particulate sample.

Chromatography, High Pressure Liquid↗
PubMed1977

Hydroxylation of aromatic compounds by reduced nicotinamide-adenine dinucleotide and phenazine methosulphate requires hydrogen peroxide and hydroxyl radicals, but not superoxide.

1. A mixture of NADH and phenazine methosulphate hydroxylates aromatic compounds at acidic pH values. 2. Hydroxylation is inhibited by catalase and by scavengers of the hydroxyl radical (-OH) but not by superoxide dismutase. 3. It is concluded that neither O2 leads to nor HO2- is sufficiently reactive to hydroxylate aromatic rings.

Hydrogen Peroxide↗
PubMed1995

Degradation of Monochlorinated and Nonchlorinated Aromatic Compounds under Iron-Reducing Conditions.

The capacity for Fe(sup3+) to serve as an electron acceptor in the microbial degradation of monochlorinated and nonchlorinated aromatic compounds was investigated in anoxic sediment enrichments. The substrates tested included phenol, benzoate, aniline, their respective monochlorinated isomers, o-, m-, and p-cresol, and all six dimethylphenol isomers. Phenol and 2-, 3-, and 4-chlorophenol were utilized by anaerobic microorganisms, with the concomitant reduction of Fe(sup3+) to Fe(sup2+). The amount of Fe(sup2+) produced in the enrichments was 89 to 138% of that expected for the stoichiometric degradation of these substrates to CO(inf2), suggesting complete mineralization at the expense of Fe reduction. Under Fe-reducing conditions, there was initial loss of benzoate and 3-chlorobenzoate but not of 2- or 4-chlorobenzoate. In addition, there was initial microbial utilization of aniline but not of the chloroaniline isomers. There was also initial loss of o-, m-, and p-cresol in our enrichments. None of the dimethylphenol isomers, however, was degraded within 300 days. Furthermore, we tested the capacity of an Fe-reducing, benzoate-grown culture of Geobacter metallireducens GS-15 to utilize monochlorinated benzoates and phenols. G. metallireducens was able to degrade benzoate and phenol but none of their chlorinated isomers, suggesting that the degradation of chlorophenols in our sediment enrichments may be due to novel Fe-reducing organisms that have yet to be isolated.

Journal Article↗
PubMed2001

Effects of simple aromatic compounds and flavonoids on Ca2+ fluxes in rat pituitary GH(4)C(1) cells.

The biological activity of phenolic compounds from plants is well documented in vitro, but little is known about the possible effect of simple aromatic compounds and flavonoids on voltage-operated Ca2+ channels (VOCCs). In pituitary cells, several intracellular pathways may regulate the activity of VOCCs. In this study, we investigated the effect of nine phenylpropanes and metanes, and 20 flavonoids on high K(+)-induced 45Ca2+ entry in clonal rat pituitary GH(4)C(1) cells. At the highest dose tested (20 microg/ml), flavone (a flavone) inhibited 45Ca2+ entry by 63.5%, naringenin (a flavanone) by 56.3% and genistein (an isoflavone) by 54.6%. The phenylmetane derivative octyl gallate was the most potent compound tested, with an IC(50) value of 15.0 microg/ml. The IC(50) value for the reference compound verapamil hydrochloride was 3.0 microg/ml. In sharp contrast to the above, the flavonols quercetin and morin potentiated 45Ca2+ entry. At 20 microg/ml, quercetin increased 45Ca2+ entry by 54.1% and morin by 48.0%. Quercetin increased the cellular cAMP content in a concentration-dependent manner. H 89, an inhibitor of protein kinase A, inhibited the effect of quercetin on 45Ca2+ entry. The results thus suggest that the effect of quercetin is the result of a protein kinase A-mediated activation of VOCCs. Quercetin induced a rapid and marked increase in both the transient (143.1+/-4.2%) and delayed (198.8+/-10.0%) Ca2+ currents, measured by the whole cell patch clamp technique. The onset of the inhibitory effect of octyl gallate was slow, but resulted in an almost complete inhibition of both Ca2+ currents.

Animals↗
PubMed1984

Polycyclic aromatic compounds in curing smoke.

The curing smoke, generated by the smouldering of alder chips, from a commercial food smoking plant was investigated with respect to polynuclear aromatic compounds (PAC). Samples were taken from inside the ovens and in the working zone immediately outside them. Analysis showed that considerable amounts of methyl phenanthrenes were present in the smoke as a major part of the PAC content.

Chromatography, Gas↗
PubMed1999

Studies on the constituents of Gliricidia sepium (Leguminosae) leaves and roots: isolation and structure elucidation of new triterpenoid saponins and aromatic compounds.

Our research program on the Central American fooder plant Gliricidia sepium led to the discovery of two new triterpene saponins (1 and 2) and known aromatic compounds. The new compounds possess 3beta,21beta, 24-trihydroxy-22-oxoolean-12-ene as an aglycon. The oligosaccharide moiety linked to C-3 of the aglycon contained two pyranoses (glucuronic acid and xylose); in addition the glucose residue of both 1 and 2 is also linked to C-21. Structure elucidation of these new compounds through the extensive use of 1D and 2D NMR techniques have provided detailed information about the sapogenin and the saccharide chains, inclusive of sugar sequence and the position of glycosylation.

Central America↗
PubMed1975

The nature of the binding site for aromatic compounds in glycogen phosphorylase b.

The inhibition of rabbit muscle glycogen phosphorylase b (1,4-alpha-D-glucan--orthophosphate alpha-glucosyltransferase, EC 2.4.1.1) by aromatic compounds was examined with 15 compounds. The relative effectiveness of the inhibitors correlated well with increasing substituent constant, pi, indicating the hydrophobic nature of the binding site. The inhibition was not affected by the ionic-strength variation of the assay mixtures. The results predict that the course of chemical modification of this enzyme and the properties of the derivatives depend on the nature of the reagent and on the incorporated groups. Many of the dissimilar and sometimes contradictory results reported for chemical-modification studies and for chemically modified phosphorylase b are explained by the findings presented in the paper.

Animals↗
PubMed1994

Photometabolism of Heterocyclic Aromatic Compounds by Rhodopseudomonas palustris OU 11.

Rhodopseudomonas palustris OU 11 (ATCC 51186; DSM 7375) isolated from a pond of chemical industry effluent could anaerobically photometabolize heterocyclic aromatic compounds belonging to the pyridine and pyrazine groups only after a period of adaptation on pyrazinoic acid of 5 to 6 weeks. Growth on heterocyclic compounds was light dependent. The effects of various concentrations of heterocyclic compounds on growth suggest that higher concentrations of these compounds inhibit growth and are toxic.

Journal Article↗
PubMed1977

Genetic regulation of UDP-glucuronosyltransferase induction by polycyclic aromatic compounds in mice. Co-segregation with aryl hydrocarbon (benzo(alpha)pyrene) hydroxylase induction.

Induction of hepatic 4-methylumbelliferone UDP-glucuronosyltransferase (EC 2.4.1.17) by polycyclic aromatic compounds, such as 3-methylcholanthrene or beta-naphthoflavone, occurs in C57BL/6N, A/J, PL/J, C3HeB/FeJ, and BALB/cJ but not in DBA/2N, AU/SsJ, AKR/J, or RF/J inbred strains of mice. This pattern of five responsive and five nonresponsive mouse strains parallels that of the Ah locus, which controls the induction of aryl hydrocarbon (benzo[alpha]pyrene) hydroxylase (EC 1.14.14.2). Induction of the transferase is maximal in C57BL/6N mice with 200 mg of 3-methylcholanthrene/kg body weight; no induction occurs in nonresponsive DBA/2N mice even at a dose of 400 mg/kg. The rise of inducible transferase activity lags 1 or more days behind the rise of inducible hydroxylase activity and peaks 5 days after a single dose of 3-methylcholanthrene. In offspring from the appropriate backcrosses and intercross between C57BL/6N and DBA/2N parent strains, the genetic expression of 3-methylcholanthrene-inducible transferase activity is inherited as an additive (co-dominant) trait. This expression differs distinctly from that of the inducible hydroxylase activity, which is inherited almost exclusively as a single autosomal dominant trait in these same animals. The more potent inducer 2,3,7,8-tetrachlorodibenzo-p-dioxin induces the transferase more than 3-fold in C57BL/6N mice and less than 2-fold in DBA/2N mice, whereas the hydroxylase is induced equally (about 8-fold) in both strains. A dose of 3-methylcholanthrene given 3 days after 2,3,7,8-tetrachlorodibenzo-p-dioxin, at a time when hydroxylase induction in both strains is very high, does not enhance the rise in inducible transferase activity seen in C57BL/6N or DBA/2N mice which have received 2,3,7,8-tetrachlorodibenzo-p-dioxin alone. These data indicate that (a) the inducibility of two metabolically coordinated membrane-bound enzyme activities may be regulated by a single genetic locus, and (b) although the hydroxylase can be fully induced in the nonresponsive DBA/2N strain by 2,3,7,8-tetrachlorodibenzo-p-dioxin prior to 3-methylcholanthrene treatment, metabolites of the 3-methylcholanthrene treatment, metabolites of the 3-methylcholanthrene treatment, metabolites of the 3-methylcholanthrene, presumably present in the liver, are incapable of inducing further the transferase activity. The difference in sensitivity between 3-methylcholanthrene and the more potent inducer 2,3,7,8-tetrachlorodibenzo-p-dioxin for both the hydroxylase and the transferase activities suggests the possibility of a common receptor in regulating both enzyme induction processes.

Age Factors↗