The Experts below are selected from a list of 120 Experts worldwide ranked by ideXlab platform
Kenneth N. Timmis - One of the best experts on this subject based on the ideXlab platform.
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polychlorinated biphenyl degrading microbial communities in soils and sediments
Current Opinion in Microbiology, 2002Co-Authors: Wolfrainer Abraham, Balbina Nogales, Peter N Golyshin, Dietmar H Pieper, Kenneth N. TimmisAbstract:Abstract Recent advances in the degradation of polychlorinated biphenyls (PCBs) have focussed on the use of experimental enrichment cultures to obtain PCB-degrading communities, and the use of culture-independent approaches to characterize natural and experimental PCB-degrading communities and to identify the key members in this process. PCB-degrading communities can be surprisingly diverse. Novel types of composite bacteria–mineral biofilm communities have been described. Community metabolism of PCBs may lead to the formation of Protoanemonin, a dead-end product in some instances but, in others, a seemingly productive intermediate. Analysis of isotope fractionation and preferred enantiomer degradation has provided new information on degradation of PCBs in anaerobic settings. The first defined community capable of dehalorespiration of PCBs has been described, and important community members identified. Here, we provide an overview of the current knowledge of aerobic and anaerobic degradation of PCBs in microbial consortia and in the environment, including novel approaches to determine in situ PCB degradation.
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towards elucidation of microbial community metabolic pathways unravelling the network of carbon sharing in a pollutant degrading bacterial consortium by immunocapture and isotopic ratio mass spectrometry
Environmental Microbiology, 1999Co-Authors: Oliver Pelz, Kenneth N. Timmis, Michael Tesar, Rolfmichael Wittich, Edward R B Moore, Wolfrainer AbrahamAbstract:Although much information on metabolic pathways within individual organisms is available, little is known about the pathways operating in natural communities in which extensive sharing of nutritional resources is the rule. In order to analyse such a consortium pathway, we have investigated the flow of 4-chlorosalicylate as carbon substrate within a simple chemostat microbial community using 13C-labelled metabolites and isotopic ratio mass spectrometric analysis of label enrichment in immunocaptured member populations of the community. A complex pathway network of carbon sharing was thereby revealed, involving two different metabolic routes, one of which is completely novel and involves the toxic metabolite Protoanemonin. The high stability of the community results, at least in part, from interdependencies based on carbon sharing and the rapid removal of toxic metabolites.
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detoxification of Protoanemonin by dienelactone hydrolase
Journal of Bacteriology, 1998Co-Authors: Markus Bruckmann, Kenneth N. Timmis, Rafael Blasco, Dietmar H PieperAbstract:Protoanemonin is a toxic metabolite which may be formed during the degradation of some chloroaromatic compounds, such as polychlorinated biphenyls, by natural microbial consortia. We show here that Protoanemonin can be transformed by dienelactone hydrolase of Pseudomonas sp. strain B13 to cis-acetylacrylate. Although similar Km values were observed for cis-dienelactone and Protoanemonin, the turnover rate of Protoanemonin was only 1% that of cis-dienelactone. This indicates that at least this percentage of the enzyme is in the active state, even in the absence of activation. The trans-dienelactone hydrolase of Pseudomonas sp. strain RW10 did not detectably transform Protoanemonin. Obviously, Pseudomonas sp. strain B13 possesses at least two mechanisms to avoid Protoanemonin toxicity, namely a highly active chloromuconate cycloisomerase, which routes most of the 3-chloro-cis,cis-muconate to the cis-dienelactone, thereby largely preventing Protoanemonin formation, and dienelactone hydrolase, which detoxifies any small amount of Protoanemonin that might nevertheless be formed.
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evidence that formation of Protoanemonin from metabolites of 4 chlorobiphenyl degradation negatively affects the survival of 4 chlorobiphenyl cometabolizing microorganisms
Applied and Environmental Microbiology, 1997Co-Authors: Rafael Blasco, Kenneth N. Timmis, Rolfmichael Wittich, Megharaj Mallavarapu, Dietmar H PieperAbstract:A rapid decline in cell viability of different PCB-metabolizing organisms was observed in soil microcosms amended with 4-chlorobiphenyl. The toxic effect could not be attributed to 4-chlorobiphenyl but was due to a compound formed from the transformation of 4-chlorobiphenyl by the natural microflora. Potential metabolites of 4-chlorobiphenyl, 4-chlorobenzoate and 4-chlorocatechol, caused similar toxic effects. We tested the hypothesis that the toxic effects are due to the formation of Protoanemonin, a plant-derived antibiotic, which is toxic to microorganisms and which has been shown to be formed from 4-chlorocatechol by enzymes of the 3-oxoadipate pathway. Consistent with our hypothesis, addition to soil microcosms of strains able to reroute intermediary 4-chlorocatechol from the 3-oxoadipate pathway and into the meta-cleavage pathway or able to mineralize 4-chlorocatechol by a modified ortho-cleavage pathway resulted in reversal of this toxic effect. Surprisingly, while direct addition of Protoanemonin influenced both the viability of fungi and the microbial activity of the soil microcosm, there was little effect on bacterial viability due to its rapid degradation. This rapid degradation accounts for our inability to detect this compound in soils amended with 4-chlorocatechol. However, significant accumulation of Protoanemonin was observed by a mixed bacterial community enriched with benzoate or a mixture of benzoate and 4-methylbenzoate, providing the metabolic potential of the soil to form Protoanemonin. The effects of soil heterogeneity and microcosm interactions are discussed in relation to the different effects of Protoanemonin when applied as a shock load and when it is produced in small amounts from precursors over long periods.
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from xenobiotic to antibiotic formation of Protoanemonin from 4 chlorocatechol by enzymes of the 3 oxoadipate pathway
Journal of Biological Chemistry, 1995Co-Authors: Rafael Blasco, Kenneth N. Timmis, Rolfmichael Wittich, Megharaj Mallavarapu, Dietmar H PieperAbstract:Chloroaromatics, a major class of industrial pollutants, may be oxidatively metabolized to chlorocatechols by soil and water microorganisms that have evolved catabolic activities toward these xenobiotics. We show here that 4-chlorocatechol can be further transformed by enzymes of the ubiquitous 3-oxoadipate pathway. However, whereas chloromuconate cycloisomerases catalyze the dechlorination of 3-chloro-cis,cis-muconate to form cis-dienelactone, muconate cycloisomerases catalyze a novel reaction, i.e. the dechlorination and concomitant decarboxylation to form 4-methylenebut-2-en-4-olide (Protoanemonin), an ordinarily plant-derived antibiotic that is toxic to microorganisms.
Dietmar H Pieper - One of the best experts on this subject based on the ideXlab platform.
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formation of Protoanemonin from 2 chloro cis cis muconate by the combined action of muconate cycloisomerase and muconolactone isomerase
Journal of Bacteriology, 2002Co-Authors: Anke Skiba, Volker Hecht, Dietmar H PieperAbstract:Muconate cycloisomerases are known to catalyze the reversible conversion of 2-chloro-cis,cis-muconate by 1,4- and 3,6-cycloisomerization into (4S)-(+)-2-chloro- and (4R/5S)-(+)-5-chloromuconolactone. 2-Chloromuconolactone is transformed by muconolactone isomerase with concomitant dechlorination and decarboxylation into the antibiotic Protoanemonin. The low kcat for this compound compared to that for 5-chloromuconolactone suggests that Protoanemonin formation is of minor importance. However, since 2-chloromuconolactone is the initially predominant product of 2-chloromuconate cycloisomerization, significant amounts of Protoanemonin were formed in reaction mixtures containing large amounts of muconolactone isomerase and small amounts of muconate cycloisomerase. Such enzyme ratios resemble those observed in cell extracts of benzoate-grown cells of Ralstonia eutropha JMP134. In contrast, cis-dienelactone was the predominant product formed by enzyme preparations, in which muconolactone isomerase was in vitro rate limiting. In reaction mixtures containing chloromuconate cycloisomerase and muconolactone isomerase, only minute amounts of Protoanemonin were detected, indicating that only small amounts of 2-chloromuconolactone were formed by cycloisomerization and that chloromuconate cycloisomerase actually preferentially catalyzes a 3,6-cycloisomerization.
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polychlorinated biphenyl degrading microbial communities in soils and sediments
Current Opinion in Microbiology, 2002Co-Authors: Wolfrainer Abraham, Balbina Nogales, Peter N Golyshin, Dietmar H Pieper, Kenneth N. TimmisAbstract:Abstract Recent advances in the degradation of polychlorinated biphenyls (PCBs) have focussed on the use of experimental enrichment cultures to obtain PCB-degrading communities, and the use of culture-independent approaches to characterize natural and experimental PCB-degrading communities and to identify the key members in this process. PCB-degrading communities can be surprisingly diverse. Novel types of composite bacteria–mineral biofilm communities have been described. Community metabolism of PCBs may lead to the formation of Protoanemonin, a dead-end product in some instances but, in others, a seemingly productive intermediate. Analysis of isotope fractionation and preferred enantiomer degradation has provided new information on degradation of PCBs in anaerobic settings. The first defined community capable of dehalorespiration of PCBs has been described, and important community members identified. Here, we provide an overview of the current knowledge of aerobic and anaerobic degradation of PCBs in microbial consortia and in the environment, including novel approaches to determine in situ PCB degradation.
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detoxification of Protoanemonin by dienelactone hydrolase
Journal of Bacteriology, 1998Co-Authors: Markus Bruckmann, Kenneth N. Timmis, Rafael Blasco, Dietmar H PieperAbstract:Protoanemonin is a toxic metabolite which may be formed during the degradation of some chloroaromatic compounds, such as polychlorinated biphenyls, by natural microbial consortia. We show here that Protoanemonin can be transformed by dienelactone hydrolase of Pseudomonas sp. strain B13 to cis-acetylacrylate. Although similar Km values were observed for cis-dienelactone and Protoanemonin, the turnover rate of Protoanemonin was only 1% that of cis-dienelactone. This indicates that at least this percentage of the enzyme is in the active state, even in the absence of activation. The trans-dienelactone hydrolase of Pseudomonas sp. strain RW10 did not detectably transform Protoanemonin. Obviously, Pseudomonas sp. strain B13 possesses at least two mechanisms to avoid Protoanemonin toxicity, namely a highly active chloromuconate cycloisomerase, which routes most of the 3-chloro-cis,cis-muconate to the cis-dienelactone, thereby largely preventing Protoanemonin formation, and dienelactone hydrolase, which detoxifies any small amount of Protoanemonin that might nevertheless be formed.
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evidence that formation of Protoanemonin from metabolites of 4 chlorobiphenyl degradation negatively affects the survival of 4 chlorobiphenyl cometabolizing microorganisms
Applied and Environmental Microbiology, 1997Co-Authors: Rafael Blasco, Kenneth N. Timmis, Rolfmichael Wittich, Megharaj Mallavarapu, Dietmar H PieperAbstract:A rapid decline in cell viability of different PCB-metabolizing organisms was observed in soil microcosms amended with 4-chlorobiphenyl. The toxic effect could not be attributed to 4-chlorobiphenyl but was due to a compound formed from the transformation of 4-chlorobiphenyl by the natural microflora. Potential metabolites of 4-chlorobiphenyl, 4-chlorobenzoate and 4-chlorocatechol, caused similar toxic effects. We tested the hypothesis that the toxic effects are due to the formation of Protoanemonin, a plant-derived antibiotic, which is toxic to microorganisms and which has been shown to be formed from 4-chlorocatechol by enzymes of the 3-oxoadipate pathway. Consistent with our hypothesis, addition to soil microcosms of strains able to reroute intermediary 4-chlorocatechol from the 3-oxoadipate pathway and into the meta-cleavage pathway or able to mineralize 4-chlorocatechol by a modified ortho-cleavage pathway resulted in reversal of this toxic effect. Surprisingly, while direct addition of Protoanemonin influenced both the viability of fungi and the microbial activity of the soil microcosm, there was little effect on bacterial viability due to its rapid degradation. This rapid degradation accounts for our inability to detect this compound in soils amended with 4-chlorocatechol. However, significant accumulation of Protoanemonin was observed by a mixed bacterial community enriched with benzoate or a mixture of benzoate and 4-methylbenzoate, providing the metabolic potential of the soil to form Protoanemonin. The effects of soil heterogeneity and microcosm interactions are discussed in relation to the different effects of Protoanemonin when applied as a shock load and when it is produced in small amounts from precursors over long periods.
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from xenobiotic to antibiotic formation of Protoanemonin from 4 chlorocatechol by enzymes of the 3 oxoadipate pathway
Journal of Biological Chemistry, 1995Co-Authors: Rafael Blasco, Kenneth N. Timmis, Rolfmichael Wittich, Megharaj Mallavarapu, Dietmar H PieperAbstract:Chloroaromatics, a major class of industrial pollutants, may be oxidatively metabolized to chlorocatechols by soil and water microorganisms that have evolved catabolic activities toward these xenobiotics. We show here that 4-chlorocatechol can be further transformed by enzymes of the ubiquitous 3-oxoadipate pathway. However, whereas chloromuconate cycloisomerases catalyze the dechlorination of 3-chloro-cis,cis-muconate to form cis-dienelactone, muconate cycloisomerases catalyze a novel reaction, i.e. the dechlorination and concomitant decarboxylation to form 4-methylenebut-2-en-4-olide (Protoanemonin), an ordinarily plant-derived antibiotic that is toxic to microorganisms.
Wolfrainer Abraham - One of the best experts on this subject based on the ideXlab platform.
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polychlorinated biphenyl degrading microbial communities in soils and sediments
Current Opinion in Microbiology, 2002Co-Authors: Wolfrainer Abraham, Balbina Nogales, Peter N Golyshin, Dietmar H Pieper, Kenneth N. TimmisAbstract:Abstract Recent advances in the degradation of polychlorinated biphenyls (PCBs) have focussed on the use of experimental enrichment cultures to obtain PCB-degrading communities, and the use of culture-independent approaches to characterize natural and experimental PCB-degrading communities and to identify the key members in this process. PCB-degrading communities can be surprisingly diverse. Novel types of composite bacteria–mineral biofilm communities have been described. Community metabolism of PCBs may lead to the formation of Protoanemonin, a dead-end product in some instances but, in others, a seemingly productive intermediate. Analysis of isotope fractionation and preferred enantiomer degradation has provided new information on degradation of PCBs in anaerobic settings. The first defined community capable of dehalorespiration of PCBs has been described, and important community members identified. Here, we provide an overview of the current knowledge of aerobic and anaerobic degradation of PCBs in microbial consortia and in the environment, including novel approaches to determine in situ PCB degradation.
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towards elucidation of microbial community metabolic pathways unravelling the network of carbon sharing in a pollutant degrading bacterial consortium by immunocapture and isotopic ratio mass spectrometry
Environmental Microbiology, 1999Co-Authors: Oliver Pelz, Kenneth N. Timmis, Michael Tesar, Rolfmichael Wittich, Edward R B Moore, Wolfrainer AbrahamAbstract:Although much information on metabolic pathways within individual organisms is available, little is known about the pathways operating in natural communities in which extensive sharing of nutritional resources is the rule. In order to analyse such a consortium pathway, we have investigated the flow of 4-chlorosalicylate as carbon substrate within a simple chemostat microbial community using 13C-labelled metabolites and isotopic ratio mass spectrometric analysis of label enrichment in immunocaptured member populations of the community. A complex pathway network of carbon sharing was thereby revealed, involving two different metabolic routes, one of which is completely novel and involves the toxic metabolite Protoanemonin. The high stability of the community results, at least in part, from interdependencies based on carbon sharing and the rapid removal of toxic metabolites.
Rolfmichael Wittich - One of the best experts on this subject based on the ideXlab platform.
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towards elucidation of microbial community metabolic pathways unravelling the network of carbon sharing in a pollutant degrading bacterial consortium by immunocapture and isotopic ratio mass spectrometry
Environmental Microbiology, 1999Co-Authors: Oliver Pelz, Kenneth N. Timmis, Michael Tesar, Rolfmichael Wittich, Edward R B Moore, Wolfrainer AbrahamAbstract:Although much information on metabolic pathways within individual organisms is available, little is known about the pathways operating in natural communities in which extensive sharing of nutritional resources is the rule. In order to analyse such a consortium pathway, we have investigated the flow of 4-chlorosalicylate as carbon substrate within a simple chemostat microbial community using 13C-labelled metabolites and isotopic ratio mass spectrometric analysis of label enrichment in immunocaptured member populations of the community. A complex pathway network of carbon sharing was thereby revealed, involving two different metabolic routes, one of which is completely novel and involves the toxic metabolite Protoanemonin. The high stability of the community results, at least in part, from interdependencies based on carbon sharing and the rapid removal of toxic metabolites.
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evidence that formation of Protoanemonin from metabolites of 4 chlorobiphenyl degradation negatively affects the survival of 4 chlorobiphenyl cometabolizing microorganisms
Applied and Environmental Microbiology, 1997Co-Authors: Rafael Blasco, Kenneth N. Timmis, Rolfmichael Wittich, Megharaj Mallavarapu, Dietmar H PieperAbstract:A rapid decline in cell viability of different PCB-metabolizing organisms was observed in soil microcosms amended with 4-chlorobiphenyl. The toxic effect could not be attributed to 4-chlorobiphenyl but was due to a compound formed from the transformation of 4-chlorobiphenyl by the natural microflora. Potential metabolites of 4-chlorobiphenyl, 4-chlorobenzoate and 4-chlorocatechol, caused similar toxic effects. We tested the hypothesis that the toxic effects are due to the formation of Protoanemonin, a plant-derived antibiotic, which is toxic to microorganisms and which has been shown to be formed from 4-chlorocatechol by enzymes of the 3-oxoadipate pathway. Consistent with our hypothesis, addition to soil microcosms of strains able to reroute intermediary 4-chlorocatechol from the 3-oxoadipate pathway and into the meta-cleavage pathway or able to mineralize 4-chlorocatechol by a modified ortho-cleavage pathway resulted in reversal of this toxic effect. Surprisingly, while direct addition of Protoanemonin influenced both the viability of fungi and the microbial activity of the soil microcosm, there was little effect on bacterial viability due to its rapid degradation. This rapid degradation accounts for our inability to detect this compound in soils amended with 4-chlorocatechol. However, significant accumulation of Protoanemonin was observed by a mixed bacterial community enriched with benzoate or a mixture of benzoate and 4-methylbenzoate, providing the metabolic potential of the soil to form Protoanemonin. The effects of soil heterogeneity and microcosm interactions are discussed in relation to the different effects of Protoanemonin when applied as a shock load and when it is produced in small amounts from precursors over long periods.
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from xenobiotic to antibiotic formation of Protoanemonin from 4 chlorocatechol by enzymes of the 3 oxoadipate pathway
Journal of Biological Chemistry, 1995Co-Authors: Rafael Blasco, Kenneth N. Timmis, Rolfmichael Wittich, Megharaj Mallavarapu, Dietmar H PieperAbstract:Chloroaromatics, a major class of industrial pollutants, may be oxidatively metabolized to chlorocatechols by soil and water microorganisms that have evolved catabolic activities toward these xenobiotics. We show here that 4-chlorocatechol can be further transformed by enzymes of the ubiquitous 3-oxoadipate pathway. However, whereas chloromuconate cycloisomerases catalyze the dechlorination of 3-chloro-cis,cis-muconate to form cis-dienelactone, muconate cycloisomerases catalyze a novel reaction, i.e. the dechlorination and concomitant decarboxylation to form 4-methylenebut-2-en-4-olide (Protoanemonin), an ordinarily plant-derived antibiotic that is toxic to microorganisms.
Vitor A. P. Martins Dos Santos - One of the best experts on this subject based on the ideXlab platform.
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Protoanemonin: a natural quorum sensing inhibitor that selectively activates iron starvation response
Environmental microbiology, 2012Co-Authors: Roberto A. Bobadilla Fazzini, Michael Givskov, Mette E. Skindersoe, Piotr Bielecki, Jacek Puchałka, Vitor A. P. Martins Dos SantosAbstract:Many Gram-negative bacteria employ cell-to-cell communication mediated by N-acyl homoserine lactones (quorum sensing) to control expression of a wide range of genes including, but not limited to, genes encoding virulence factors. Outside the laboratory, the bacteria live in complex communities where signals may be perceived across species. We here present a newly found natural quorum sensing inhibitor, produced by the pseudomonads Pseudomonas sp. B13 and Pseudomonas reinekei MT1 as a blind end in the biodegradation of organochloride xenobiotics, which inhibits quorum sensing in P. aeruginosa in naturally occurring concentrations. This catabolite, 4-methylenebut-2-en-4-olide, also known as Protoanemonin, has been reported to possess antibacterial properties, but seems to have dual functions. Using transcriptomics and proteomics, we found that Protoanemonin significantly reduced expression of genes and secretion of proteins known to be under control of quorum sensing in P. aeruginosa. Moreover, we found activation of genes and gene products involved in iron starvation response. It is thus likely that inhibition of quorum sensing, as the production of antibiotics, is a phenomenon found in complex bacterial communities.
