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A Stolz

Publications and source records attributed to A Stolz.

At least 55 records · Page 3Linked to original sources
PubMed1999

Description of Pseudaminobacter gen. nov. with two new species, Pseudaminobacter salicylatoxidans sp. nov. and Pseudaminobacter defluvii sp. nov.

An aerobic bacterium, strain BN12T, which degrades substituted naphthalenesulfonates and substituted salicylates was isolated from a 6-aminonaphthalene-2-sulfonate-degrading microbial consortium originating from the River Elbe, Germany. Chemotaxonomic investigations of quinones, polyamines and polar lipids allowed allocation of this strain to the alpha-subclass of the Proteobacteria and revealed similarity to species of the genera Aminobacter, Chelatobacter and Mesorhizobium. This was confirmed by typing with 16S rRNA-targeted oligonucleotide probes and 16S rDNA sequencing and phylogenetic analysis, indicating that BN12T clusters most closely with a strain 'Thiobacillus' THI 051T and with the above genera but comprising a separate branch. DNA-DNA hybridizations demonstrated that strain BN12T is different from all species of Aminobacter currently described and recognized. The fatty acid patterns, substrate utilization profile and biochemical characteristics displayed no obvious similarity to the characteristics of Aminobacter and Chelatobacter species. 'Thiobacillus' THI 051T, however, revealed phenotypic similarities to BN12T. Furthermore, 16S rRNA sequences of Chelatobacter heintzii showed a high similarity to the 16S rRNA sequences of all currently recognized Aminobacter species. On the basis of these and previously published results, the new genus Pseudaminobacter is proposed, harbouring the two new species Pseudaminobacter salicylatoxidans sp. nov. and Pseudaminobacter defluvii sp. nov. The type strains are BN12T (= DSM 6986T) and THI 051T (= IFO 14570T), respectively.

Bacterial Typing Techniques↗
PubMed1999

Catalytic properties of the 3-chlorocatechol-oxidizing 2, 3-dihydroxybiphenyl 1,2-dioxygenase from Sphingomonas sp. strain BN6.

The 2,3-dihydroxybiphenyl dioxygenase from Sphingomonas sp. strain BN6 (BphC1-BN6) differs from most other extradiol dioxygenases by its ability to oxidize 3-chlorocatechol to 3-chloro-2-hydroxymuconic semialdehyde by a distal cleavage mechanism. The turnover of different substrates and the effects of various inhibitors on BphC1-BN6 were compared with those of another 2,3-dihydroxybiphenyl dioxygenase from the same strain (BphC2-BN6) as well as with those of the archetypical catechol 2,3-dioxygenase (C23O-mt2) encoded by the TOL plasmid. Cell extracts containing C23O-mt2 or BphC2-BN6 converted the relevant substrates with an almost constant rate for at least 10 min, whereas BphC1-BN6 was inactivated significantly within the first minutes during the turnover of all substrates tested. Furthermore, BphC1-BN6 was much more sensitive than the other two enzymes to inactivation by the Fe(II) ion-chelating compound o-phenanthroline. The reason for inactivation of BphC1-BN6 appeared to be the loss of the weakly bound ferrous ion, which is the cofactor in the catalytic center. A mutant enzyme of BphC1-BN6 constructed by site-directed mutagenesis showed a higher stability to inactivation by o-phenanthroline and an increased catalytic efficiency for the conversion of 2,3-dihydroxybiphenyl and 3-methylcatechol but was still inactivated during substrate oxidation.

Catalytic Domain↗
PubMed1998

Isolation of a bacterial strain with the ability to utilize the sulfonated azo compound 4-carboxy-4'-sulfoazobenzene as the sole source of carbon and energy.

A bacterial strain (strain S5) which grows aerobically with the sulfonated azo compound 4-carboxy-4'-sulfoazobenzene as the sole source of carbon and energy was isolated. This strain was obtained by continuous adaptation of "Hydrogenophaga palleronii" S1, which has the ability to grow aerobically with 4-aminobenzenesulfonate. Strain S5 probably cleaves 4-carboxy-4'-sulfoazobenzene reductively under aerobic conditions to 4-aminobenzoate and 4-aminobenzene-sulfonate, which are mineralized by previously established degradation pathways.

Azo Compounds↗
PubMed1998

Initial transformations in the biodegradation of benzothiazoles by Rhodococcus isolates.

Benzothiazole-2-sulfonate (BTSO3) is one of the side products occurring in 2-mercaptobenzothiazole (MBT) production wastewater. We are the first to isolate an axenic culture capable of BTSO3 degradation. The isolate was identified as a Rhodococcus erythropolis strain and also degraded 2-hydroxybenzothiazole (OBT) and benzothiazole (BT), but not MBT, which was found to inhibit the biodegradation of OBT, BT, and BTSO3. In anaerobic resting cell assays, BTSO3 was transformed into OBT in stoichiometric amounts. Under aerobic conditions, OBT was observed as an intermediate in BT breakdown and an unknown compound transiently accumulated in several assays. This product was identified as a dihydroxybenzothiazole. Benzothiazole degradation pathways seem to converge into OBT, which is then transformed further into the dihydroxy derivative.

Aerobiosis↗
PubMed1998

Distal cleavage of 3-chlorocatechol by an extradiol dioxygenase to 3-chloro-2-hydroxymuconic semialdehyde.

A 2,3-dihydroxybiphenyl 1,2-dioxygenase from the naphthalenesulfonate-degrading bacterium Sphingomonas sp. strain BN6 oxidized 3-chlorocatechol to a yellow product with a strongly pH-dependent absorption maximum at 378 nm. A titration curve suggested (de)protonation of an ionizable group with a pKa of 4.4. The product was isolated, purified, and converted, by treatment with diazomethane, to a dimethyl derivative and, by incubation with ammonium chloride, to a picolinic acid derivative. Mass spectra and 1H and 13C nuclear magnetic resonance (NMR) data for these two derivatives prove a 3-chloro-2-hydroxymuconic semialdehyde structure for the metabolite, resulting from distal (1,6) cleavage of 3-chlorocatechol. 3-Methylcatechol and 2,3-dihydroxybiphenyl are oxidized by this enzyme, in contrast, via proximal (2,3) cleavage.

Aldehydes↗
PubMed1997

Formation of a Chiral Hydroxamic Acid with an Amidase from Rhodococcus erythropolis MP50 and Subsequent Chemical Lossen Rearrangement to a Chiral Amine.

The amidase from Rhodococcus erythropolis MP50 demonstrated, in the presence of hydroxylamine, acyltransferase activity and catalyzed the formation of hydroxamates from amides and hydroxylamine. The rates of acyltransferase activity of the purified amidase for the substrates acetamide, phenylacetamide, and 2-phenylpropionamide were higher than the corresponding rates for the hydrolysis reactions. With the substrate 2-phenylpropionamide the hydrolysis reaction and the acyltransferase activity were highly enantioselective. The optically active 2-phenylpropionhydroxamate was converted by a chemical Lossen rearrangement in an aqueous medium into the enantiopure S-1-phenylethylamine.

Journal Article↗
PubMed1997

Reduction of azo dyes by redox mediators originating in the naphthalenesulfonic acid degradation pathway of Sphingomonas sp. strain BN6.

The anaerobic reduction of azo dyes by Sphingomonas sp. strain BN6 was analyzed. Aerobic conversion of 2-naphthalenesulfonate (2NS) by cells of strain BN6 stimulated the subsequent anaerobic reduction of the sulfonated azo dye amaranth at least 10-fold. In contrast, in crude extracts, the azo reductase activity was not stimulated. A mutant of strain BN6 which was not able to metabolize 2NS showed increased amaranth reduction rates only when the cells were resuspended in the culture supernatant of 2NS-grown BN6 wild-type cells. The same increase could be observed with different bacterial strains. This suggested the presence of an extracellular factor which was formed during the degradation of 2NS by strain BN6. The addition of 1,2-dihydroxynaphthalene, the first intermediate of the degradation pathway of 2NS, or its decomposition products to cell suspensions of the mutant of strain BN6 (2NS-) increased the activity of amaranth reduction. The presence of bacterial cells was needed to maintain the reduction process. Thus, the decomposition products of 1,2-dihydroxynaphthalene are suggested to act as redox mediators which are able to anaerobically shuttle reduction equivalents from the cells to the extracellular azo dye.

Amaranth Dye↗
PubMed1997

Localization of the Enzyme System Involved in Anaerobic Reduction of Azo Dyes by Sphingomonas sp. Strain BN6 and Effect of Artificial Redox Mediators on the Rate of Azo Dye Reduction.

The effect of different artificial redox mediators on the anaerobic reduction of azo dyes by Sphingomonas sp. strain BN6 or activated sludge was investigated. Reduction rates were greatly enhanced in the presence of sulfonated anthraquinones. For strain BN6, the presence of both cytoplasmic and membrane-bound azo reductase activities was shown.

Journal Article↗
PubMed1996

Degradation of benzene 1,3-disulfonate by a mixed bacterial culture.

A benzene 1,3-disulfonate degrading mixed bacterial culture was isolated from the River Elbe downstream of Hamburg. The mixed culture was composed of five different bacterial strains. None of these strains grew in axenic culture with benzene 1,3-disulfonate as sole source of carbon and energy. In the presence of 4-nitrocatechol, resting cells of the mixed culture converted benzene 1,3-disulfonate to catechol 4-sulfonate. Experiments with cell-free extracts demonstrated that catechol 4-sulfonate was further metabolized via 3-sulfomuconate and 4-carboxymethyl-4-sulfobut-2-en-4-olide.

Benzenesulfonates↗
PubMed1996

Degradation of 4-aminobenzenesulfonate by a two-species bacterial coculture. Physiological interactions between Hydrogenophaga palleronii S1 and Agrobacterium radiobacter S2.

The mutualistic interactions in a 4-aminobenzenesulfonate (sulfanilate) degrading mixed bacterial culture were studied. This coculture consisted of Hydrogenophaga palleronii strain S1 and Agrobacterium radiobacter strain S2. In this coculture only strain S1 desaminated sulfanilate to catechol-4-sulfonate, which did not accumulate in the medium but served as growth substrate for strain S2. During growth in batch culture with sulfanilate as sole source of carbon, energy, nitrogen and sulfur, the relative cell numbers (colony forming units) of both strains were almost constant. None of the strains reached a cell number which was more than threefold higher than the cell number of the second strain. A mineral medium with sulfanilate was inoculated with different relative cell numbers of both strains (relative number of colony forming units S1:S2 2200:1 to 1:500). In all cases, growth was found and the proportion of both strains moved towards an about equal value of about 3:1 (strain S1:strain S2). In contrast to the coculture, strain S1 did not grow in a mineral medium in axenic culture with 4-aminobenzenesulfonate or any other simple organic compound tested. A sterile culture supernatant from strain S2 enabled strain S1 to grow with 4-aminobenzenesulfonate. The same growth promoting effect was found after the addition of a combination of 4-aminobenzoate, biotin and vitamin B12. Strain S1 grew with 4-aminobenzenesulfonate plus the three vitamins with about the same growth rate as the mixed culture in a mineral medium. When (resting) cells of strain S1 were incubated in a pure mineral medium with sulfanilate, up to 30% of the oxidized sulfanilate accumulated as catechol-4-sulfonate in the culture medium. In contrast, only minor amounts of catechol-4-sulfonate accumulated when strain S1 was grown with 4ABS in the presence of the vitamins.

Benzenesulfonates↗
PubMed1996

Purification and characterization of a novel type of protocatechuate 3,4-dioxygenase with the ability to oxidize 4-sulfocatechol.

4-Aminobenzenesulfonate is degraded via 4-sulfocatechol by a mixed bacterial culture that consists of Hydrogenophaga palleronii strain S1 and Agrobacterium radiobacter strain S2. From the 4-sulfocatechol-degrading organism A. radiobacter strain S2, a dioxygenase that converted 4-sulfocatechol to 3-sulfomuconate was purified to homogeneity. The purified enzyme also converted protocatechuate with a similar catalytic activity to 3-carboxy-cis, cis-muconate. Furthermore, the purified enzyme oxidized 3, 4-dihydroxyphenylacetate, 3,4-dihydroxycinnamate, catechol, and 3- and 4-methylcatechol. The enzyme had a mol. wt. of about 97,400 as determined by gel filtration and consisted of two different types of subunits with mol. wt. of about 23,000 and 28,500. The NH2-terminal amino acid sequences of the two subunits were determined. An isofunctional dioxygenase was partially purified from H. palleronii strain S1. A. radiobacter strain S2 also induced, after growth with 4-sulfocatechol, an rising dbl quote, "ordinary" protocatechuate 3,4-dioxygenase that did not oxidize 4-sulfocatechol. This enzyme was also purified to homogeneity, and its catalytic and structural characteristics were compared to the "4-sulfocatechol-dioxygenase" from the same strain.

Amino Acid Sequence↗
PubMed1996

Down-regulation of expression and function of the rat liver Na+/bile acid cotransporter in extrahepatic cholestasis.

BACKGROUND & AIMS: The molecular regulation of hepatic bile acid transporters during cholestasis is largely unknown. Cloning of complementary DNAs for the sinusoidal sodium-dependent taurocholate cotransporting polypeptide (ntcp), the cytosolic bile acid-binding protein 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD), and a putative canalicular bile acid transporter Ca2+, Mg(2+)-ecto-adenosine triphosphatase, now facilitates such studies. METHODS: Protein mass, steady-state messenger RNA (mRNA) levels, and gene transcription were assessed in rat livers after common bile duct ligation (CBDL) from 1-7 days, and taurocholate uptake was determined in isolated hepatocytes. RESULTS: After CBDL, Na(+)-dependent taurocholate uptake (Vmax) declined by 70%. The levels of ntcp protein were reduced by more than 90%, and 3 alpha-HSD levels decreased by 66% by 7 days. Expression and canalicular localization of the ecto-adenosine triphosphatase remained unchanged. mRNA levels for both ntcp and 3 alpha-HSD diminished by about 60% 1 day after CBDL and remained unchanged up to 7 days. Transcriptional activity was decreased 1 day after CBDL only for ntcp. CONCLUSIONS: Extrahepatic cholestasis results in rapid down-regulation of Na(+)-dependent taurocholate uptake, ntcp transcription, and posttranscriptional regulation of both ntcp and 3 alpha-HSD mRNA. This selective decline of ntcp may represent a protective feedback mechanism in cholestasis to diminish uptake of potentially hepatotoxic bile acids.

3-Hydroxysteroid Dehydrogenases↗
PubMed1996

Purification and properties of an amidase from Rhodococcus erythropolis MP50 which enantioselectively hydrolyzes 2-arylpropionamides.

An enantioselective amidase from Rhodococcus erythropolis MP50 was purified to homogeneity. The enzyme has a molecular weight of about 480,000 and is composed of identical subunits with molecular weights of about 61,000. The NH2-terminal amino acid sequence was significantly different from previously published sequences of bacterial amidases. The purified amidase hydrolyzed a wide range of aliphatic and aromatic amides, The highest enzyme activities were found with amides carrying hydrophobic residues, such as pentyl or naphthoyl. The purified enzyme converted racemic 2-phenylpropionamide, naproxen amide [2-(6-methoxy-2-naphthyl) propionamide], and ketoprofen amide [2-(3'-benzoylphenyl)propionamide] to the corresponding S-acids with an enantiomeric excess of >99% and an almost 50% conversion of the racemic amides. The enzyme also hydrolyzed different alpha-amino amides but without significant enantioselectivity.

Amidohydrolases↗
PubMed1995

Characterization of a 2,3-dihydroxybiphenyl dioxygenase from the naphthalenesulfonate-degrading bacterium strain BN6.

An extradiol dioxygenase was cloned from the naphthalenesulfonate-degrading bacterial strain BN6 by screening a gene bank for colonies with 2,3-dihydroxybiphenyl dioxygenase activity. DNA sequence analysis of a 1,358-bp fragment revealed an open reading frame of only 486 bp. This is the smallest gene encoding an extradiol dioxygenase found until now. Expression of the gene in a T7 expression vector enabled purification of the enzyme. Gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed that the protein was a dimer with a subunit size of 21.7 kDa. The enzyme oxidized 2,3-dihydroxybiphenyl, 3-isopropylcatechol, 3- and 4-chlorocatechol, and 3- and 4-methylcatechol. Since the ability to convert 3-chlorocatechol is an unusual characteristic for an extradiol-cleaving dioxygenase, this reaction was analyzed in more detail. The deduced amino-terminal amino acid sequence differed from the corresponding sequence of the 1,2-dihydroxynaphthalene dioxygenase, which had been determined earlier from the enzyme purified from this strain. This indicates that strain BN6 carries at least two different extradiol dioxygenases.

Amino Acid Sequence↗
PubMed1994

Aerobic biodegradation of 3-aminobenzoate by gram-negative bacteria involves intermediate formation of 5-aminosalicylate as ring-cleavage substrate.

The aerobic metabolism of 3-aminobenzoate by bacteria was studied. Bacterial strains degrading 3-aminobenzoate were obtained by enrichment with 3-aminobenzoate (strain Ia3) or 5-aminosalicylate (strains BN9 and 5AS1). During growth with 3-aminobenzoate, strain Ia3 and strain 5AS1 transiently accumulated 5-aminosalicylate in the culture broth. In the presence of inhibitors of 5-aminosalicylate 1,2-dioxygenase, resting cells of all three strains converted 3-aminobenzoate to stoichiometric amounts of 5-aminosalicylate. 5-Aminosalicylate 1,2-dioxygenase activity was induced in all strains after growth with 3-aminobenzoate or 5-aminosalicylate, but not after growth in complex media.

Aminobenzoates↗
PubMed1994

Enantioselective hydrolysis of racemic naproxen nitrile and naproxen amide to S-naproxen by new bacterial isolates.

Bacteria were enriched from soil samples with succinate as a carbon source and racemic naproxen nitrile [2-(6-methoxy-2-naphthyl)propionitrile] as sole source of nitrogen. Since naproxen nitrile was only poorly soluble in water media amended with different water-immiscible organic phases were used for the enrichments. With pristane (2,6,10,14-tetramethylpentadecane) as the organic phase two bacterial strains were isolated (strain C3II and strain MP50) which were identified as rhodococci. Cells of both strains converted naproxen nitrile via naproxen amide to naproxen. From racemic naproxen nitrile Rhodococcus sp. C3II formed S-naproxen amide and subsequently S-naproxen. Racemic naproxen amide was hydrolysed to S-naproxen. Rhodococcus sp. MP50 converted racemic naproxen nitrile predominantly to R-naproxen amide and racemic naproxen amide to S-naproxen. With both strains racemic naproxen amide was converted to S-naproxen with an enantiomeric excess > 99% at a conversion rate up to 80% of the theoretical value. In strain C3II the enzymes which hydrolysed naproxen nitrile and naproxen amide were present only at a low constitutive level. In contrast, in Rhodococcus sp. MP50 these activities were induced when grown in the presence of various nitriles.

Amides↗