Oil residues containing high molecular mass hydrocarbons, rich in polyaromatic compounds, are fre... more Oil residues containing high molecular mass hydrocarbons, rich in polyaromatic compounds, are frequent end-products of crude oil processing and are poorly biodegradable. Their disposal poses an environmental problem. Through batch-enrichments from contaminated soils we have isolated and characterized seven bacterial strains that can use a residue from crude oil processing as a source of carbon and energy. The residue was a complex mixture of high molecular mass compounds, including saturated, aromatic and polycyclic aromatic hydrocarbons (PAHs). Analysis of the metabolic profiles of the strains isolated showed that they could all metabolize long-chain-length alkanes efficiently, but not PAHs. Strains degrading naphthalene, a simple PAH, did exist in the soil inocula used, but could be isolated only when enrichments were performed using pure naphthalene as the sole carbon source. All strains tested emulsified the oil residue and their ability to produce surfactants was studied.
The hydrogen isotope composition (δ 2 H) exhibits specific features that report the water conditi... more The hydrogen isotope composition (δ 2 H) exhibits specific features that report the water conditions of a wheat crop as well as the photosynthetic characteristics of the plant part considered.
Pseudomonas aeruginosa JB2 can use 2-chlorobenzoate (2-CBa), 3-CBa, 2,3-dichlorobenzoate (2,3-DCB... more Pseudomonas aeruginosa JB2 can use 2-chlorobenzoate (2-CBa), 3-CBa, 2,3-dichlorobenzoate (2,3-DCBa), and 2,5-DCBa as sole carbon and energy sources, whereas strain 142 can only grow on 2-CBa and 2,4-DCBa. Both strains, however, harbor the same halobenzoate 1,2-dioxygenase (ohbAB) and chlorocatechol (clcABD) degradation genes necessary for the metabolism of ortho-CBas. In addition, the hybABCD operon, encoding a salicylate 5-hydroxylase, is also found in both strains. The expression of ohbAB, hybABCD, and clcABD operons was measured in cultures grown on different CBas as the sole carbon source and also in glucose-grown cells supplemented with CBas as inducers. A method to standardize real-time reverse transcription-PCR experimental data was used that allows the comparison of semiquantitative mRNA accumulation in different strains and culture conditions. In both strains, the ohb and hyb systems were induced in cells grown on 2-CBa or DCBas, whereas clc was induced only by DCBas. Repre...
The aerobic cometabolism of ortho-substituted chlorobenzoates by Pseudomonas aeruginosa strain 14... more The aerobic cometabolism of ortho-substituted chlorobenzoates by Pseudomonas aeruginosa strain 142 growing on glucose-supplemented medium was analyzed. The strain, which can use 2-chlorobenzoate (2-CBA) and 2,4dichlorobenzoate (2,4-DCBA) as sole carbon and energy sources, showed high rates of 2-CBA metabolism in glucose-fed cells. In contrast, 2,4-DCBA was metabolized only after extended incubation of the full grown culture and depletion of glucose. In addition to the ortho-dehalogenation (ohb 142) genes encoding the α and β subunits of the oxygenase component of a 2-halobenzoate dioxygenase, strain 142 harbours a closely related ohbABCDFG gene cluster previously identified in P. aeruginosa JB2 (ohb JB2). The genes for the chlorocatechol ortho-catabolic pathway were identified and sequenced in this strain, showing a near complete identity with the clcABD operon of the pAC27 plasmid. Relative quantification of mRNA by RT-PCR shows a preferential induction of ohb 142 by 2-CBA, which is abolished in glucose-grown cultures. The alternate ohb JB2 and clc genes were expressed preferentially in 2,4-DCBA grown cultures. Only ohb JB2 appears to be expressed in the presence of the carbohydrate. Detection of chlorocatechol-1,2-dioxygenase activity in 2,4-DCBA plus glucose grown cultures suggests the presence of an alternate system for the ortho-cleavage of chlorobenzoates. The recruitment of elements from two halobenzoate dioxygenase systems with different induction patterns, together with a chlorocatechol degradative pathway not repressed by carbon catabolite, may allow P. aeruginosa 142 to cometabolize haloaromatics in carbohydrate grown cultures.
Oil residues containing high molecular mass hydrocarbons, rich in polyaromatic compounds, are fre... more Oil residues containing high molecular mass hydrocarbons, rich in polyaromatic compounds, are frequent end-products of crude oil processing and are poorly biodegradable. Their disposal poses an environmental problem. Through batch-enrichments from contaminated soils we have isolated and characterized seven bacterial strains that can use a residue from crude oil processing as a source of carbon and energy. The residue was a complex mixture of high molecular mass compounds, including saturated, aromatic and polycyclic aromatic hydrocarbons (PAHs). Analysis of the metabolic profiles of the strains isolated showed that they could all metabolize long-chain-length alkanes efficiently, but not PAHs. Strains degrading naphthalene, a simple PAH, did exist in the soil inocula used, but could be isolated only when enrichments were performed using pure naphthalene as the sole carbon source. All strains tested emulsified the oil residue and their ability to produce surfactants was studied.
The hydrogen isotope composition (δ 2 H) exhibits specific features that report the water conditi... more The hydrogen isotope composition (δ 2 H) exhibits specific features that report the water conditions of a wheat crop as well as the photosynthetic characteristics of the plant part considered.
Pseudomonas aeruginosa JB2 can use 2-chlorobenzoate (2-CBa), 3-CBa, 2,3-dichlorobenzoate (2,3-DCB... more Pseudomonas aeruginosa JB2 can use 2-chlorobenzoate (2-CBa), 3-CBa, 2,3-dichlorobenzoate (2,3-DCBa), and 2,5-DCBa as sole carbon and energy sources, whereas strain 142 can only grow on 2-CBa and 2,4-DCBa. Both strains, however, harbor the same halobenzoate 1,2-dioxygenase (ohbAB) and chlorocatechol (clcABD) degradation genes necessary for the metabolism of ortho-CBas. In addition, the hybABCD operon, encoding a salicylate 5-hydroxylase, is also found in both strains. The expression of ohbAB, hybABCD, and clcABD operons was measured in cultures grown on different CBas as the sole carbon source and also in glucose-grown cells supplemented with CBas as inducers. A method to standardize real-time reverse transcription-PCR experimental data was used that allows the comparison of semiquantitative mRNA accumulation in different strains and culture conditions. In both strains, the ohb and hyb systems were induced in cells grown on 2-CBa or DCBas, whereas clc was induced only by DCBas. Repre...
The aerobic cometabolism of ortho-substituted chlorobenzoates by Pseudomonas aeruginosa strain 14... more The aerobic cometabolism of ortho-substituted chlorobenzoates by Pseudomonas aeruginosa strain 142 growing on glucose-supplemented medium was analyzed. The strain, which can use 2-chlorobenzoate (2-CBA) and 2,4dichlorobenzoate (2,4-DCBA) as sole carbon and energy sources, showed high rates of 2-CBA metabolism in glucose-fed cells. In contrast, 2,4-DCBA was metabolized only after extended incubation of the full grown culture and depletion of glucose. In addition to the ortho-dehalogenation (ohb 142) genes encoding the α and β subunits of the oxygenase component of a 2-halobenzoate dioxygenase, strain 142 harbours a closely related ohbABCDFG gene cluster previously identified in P. aeruginosa JB2 (ohb JB2). The genes for the chlorocatechol ortho-catabolic pathway were identified and sequenced in this strain, showing a near complete identity with the clcABD operon of the pAC27 plasmid. Relative quantification of mRNA by RT-PCR shows a preferential induction of ohb 142 by 2-CBA, which is abolished in glucose-grown cultures. The alternate ohb JB2 and clc genes were expressed preferentially in 2,4-DCBA grown cultures. Only ohb JB2 appears to be expressed in the presence of the carbohydrate. Detection of chlorocatechol-1,2-dioxygenase activity in 2,4-DCBA plus glucose grown cultures suggests the presence of an alternate system for the ortho-cleavage of chlorobenzoates. The recruitment of elements from two halobenzoate dioxygenase systems with different induction patterns, together with a chlorocatechol degradative pathway not repressed by carbon catabolite, may allow P. aeruginosa 142 to cometabolize haloaromatics in carbohydrate grown cultures.
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