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Versatile transformations of hydrocarbons in anaerobic bacteria: substrate ranges and regio- and stereo-chemistry of activation reactions.

Jarling R, Kühner S, Basílio Janke E, Gruner A, Drozdowska M, Golding BT, Rabus R, Wilkes H - Front Microbiol (2015)

Bottom Line: In this work the metabolic activity of 11 bacterial strains during anaerobic growth with crude oil was investigated and compared with the metabolite patterns appearing during anaerobic growth with more than 40 different hydrocarbons supplied as binary mixtures.Furthermore, we demonstrate that anaerobic hydroxylation of alkylbenzenes does not only occur in denitrifiers but also in sulfate reducers.The outcomes of this study provide a basis for geochemically tracing such processes in natural habitats and contribute to an improved understanding of microbial activity in hydrocarbon-rich anoxic environments.

View Article: PubMed Central - PubMed

Affiliation: Organic Geochemistry, Chemistry of the Earth, Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences Potsdam, Germany.

ABSTRACT
Anaerobic metabolism of hydrocarbons proceeds either via addition to fumarate or by hydroxylation in various microorganisms, e.g., sulfate-reducing or denitrifying bacteria, which are specialized in utilizing n-alkanes or alkylbenzenes as growth substrates. General pathways for carbon assimilation and energy gain have been elucidated for a limited number of possible substrates. In this work the metabolic activity of 11 bacterial strains during anaerobic growth with crude oil was investigated and compared with the metabolite patterns appearing during anaerobic growth with more than 40 different hydrocarbons supplied as binary mixtures. We show that the range of co-metabolically formed alkyl- and arylalkyl-succinates is much broader in n-alkane than in alkylbenzene utilizers. The structures and stereochemistry of these products are resolved. Furthermore, we demonstrate that anaerobic hydroxylation of alkylbenzenes does not only occur in denitrifiers but also in sulfate reducers. We propose that these processes play a role in detoxification under conditions of solvent stress. The thermophilic sulfate-reducing strain TD3 is shown to produce n-alkylsuccinates, which are suggested not to derive from terminal activation of n-alkanes, but rather to represent intermediates of a metabolic pathway short-cutting fumarate regeneration by reverse action of succinate synthase. The outcomes of this study provide a basis for geochemically tracing such processes in natural habitats and contribute to an improved understanding of microbial activity in hydrocarbon-rich anoxic environments.

No MeSH data available.


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Partial ion chromatograms (upper trace, m/z 114; lower trace, m/z 226+236 + 250+264+278+292+306) of a methylated extract of strain TD3 after anaerobic growth with crude oil. Annotated peaks represent alkyl-/arylalkyl-succinates formed from respective hydrocarbon precursors. (A) Homologous series of activation products of n-alkanes in blue, branched alkanes in orange and cycloalkanes in green. The red series indicates n-alkylsuccinates not directly derived from n-alkanes (Annotation code: n-Cx, n-alkanes; 2-MC5, 2-methylpentane; brCx, branched alkanes; Cy5, cyclopentane; MCy5, methylcyclopentane; ECy5, ethylcyclopentane). (B) Succinates derived from aromatic hydrocarbons as indicated by their structures. Their respective activation positions are highlighted by black dots. (green, homologous series derived from p-n-alkyltoluenes; blue, homologous series derived from p-n-alkylethylbenzenes; magenta, succinates derived from m-dialkylbenzenes; orange, succinates derived from p-dialkylbenzenes with one branched side chain).
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Figure 1: Partial ion chromatograms (upper trace, m/z 114; lower trace, m/z 226+236 + 250+264+278+292+306) of a methylated extract of strain TD3 after anaerobic growth with crude oil. Annotated peaks represent alkyl-/arylalkyl-succinates formed from respective hydrocarbon precursors. (A) Homologous series of activation products of n-alkanes in blue, branched alkanes in orange and cycloalkanes in green. The red series indicates n-alkylsuccinates not directly derived from n-alkanes (Annotation code: n-Cx, n-alkanes; 2-MC5, 2-methylpentane; brCx, branched alkanes; Cy5, cyclopentane; MCy5, methylcyclopentane; ECy5, ethylcyclopentane). (B) Succinates derived from aromatic hydrocarbons as indicated by their structures. Their respective activation positions are highlighted by black dots. (green, homologous series derived from p-n-alkyltoluenes; blue, homologous series derived from p-n-alkylethylbenzenes; magenta, succinates derived from m-dialkylbenzenes; orange, succinates derived from p-dialkylbenzenes with one branched side chain).

Mentions: The metabolic potential and activity of alkyl-/arylalkyl-succinate formation was investigated with 11 obligately or facultatively anaerobic bacterial strains (Tables 1, 2, Supplementary Table S1). The analyses revealed a high diversity in succinate derivatives formed, especially in case of n-alkane-utilizing strains (Figure 1, Supplementary Table S3). To assign unequivocally the succinate derivatives detected in experiments with crude oil to their respective hydrocarbon-precursors, the same bacterial strains were cultivated with defined binary mixtures of a strain-specific hydrocarbon substrate and a second (mostly non growth supporting) hydrocarbon and comparatively analyzed for metabolites. Succinate derivatives can be identified as dimethyl esters in mass chromatograms due to their specific fragmentation pattern, e.g., m/z 114, 146, [M-73] as well as [M-31] and m/z 131, 145, [M-145], [M-60] as well as [M] for alkyl- and benzyl-succinates, respectively (for further details see Supplementary Material).


Versatile transformations of hydrocarbons in anaerobic bacteria: substrate ranges and regio- and stereo-chemistry of activation reactions.

Jarling R, Kühner S, Basílio Janke E, Gruner A, Drozdowska M, Golding BT, Rabus R, Wilkes H - Front Microbiol (2015)

Partial ion chromatograms (upper trace, m/z 114; lower trace, m/z 226+236 + 250+264+278+292+306) of a methylated extract of strain TD3 after anaerobic growth with crude oil. Annotated peaks represent alkyl-/arylalkyl-succinates formed from respective hydrocarbon precursors. (A) Homologous series of activation products of n-alkanes in blue, branched alkanes in orange and cycloalkanes in green. The red series indicates n-alkylsuccinates not directly derived from n-alkanes (Annotation code: n-Cx, n-alkanes; 2-MC5, 2-methylpentane; brCx, branched alkanes; Cy5, cyclopentane; MCy5, methylcyclopentane; ECy5, ethylcyclopentane). (B) Succinates derived from aromatic hydrocarbons as indicated by their structures. Their respective activation positions are highlighted by black dots. (green, homologous series derived from p-n-alkyltoluenes; blue, homologous series derived from p-n-alkylethylbenzenes; magenta, succinates derived from m-dialkylbenzenes; orange, succinates derived from p-dialkylbenzenes with one branched side chain).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4561516&req=5

Figure 1: Partial ion chromatograms (upper trace, m/z 114; lower trace, m/z 226+236 + 250+264+278+292+306) of a methylated extract of strain TD3 after anaerobic growth with crude oil. Annotated peaks represent alkyl-/arylalkyl-succinates formed from respective hydrocarbon precursors. (A) Homologous series of activation products of n-alkanes in blue, branched alkanes in orange and cycloalkanes in green. The red series indicates n-alkylsuccinates not directly derived from n-alkanes (Annotation code: n-Cx, n-alkanes; 2-MC5, 2-methylpentane; brCx, branched alkanes; Cy5, cyclopentane; MCy5, methylcyclopentane; ECy5, ethylcyclopentane). (B) Succinates derived from aromatic hydrocarbons as indicated by their structures. Their respective activation positions are highlighted by black dots. (green, homologous series derived from p-n-alkyltoluenes; blue, homologous series derived from p-n-alkylethylbenzenes; magenta, succinates derived from m-dialkylbenzenes; orange, succinates derived from p-dialkylbenzenes with one branched side chain).
Mentions: The metabolic potential and activity of alkyl-/arylalkyl-succinate formation was investigated with 11 obligately or facultatively anaerobic bacterial strains (Tables 1, 2, Supplementary Table S1). The analyses revealed a high diversity in succinate derivatives formed, especially in case of n-alkane-utilizing strains (Figure 1, Supplementary Table S3). To assign unequivocally the succinate derivatives detected in experiments with crude oil to their respective hydrocarbon-precursors, the same bacterial strains were cultivated with defined binary mixtures of a strain-specific hydrocarbon substrate and a second (mostly non growth supporting) hydrocarbon and comparatively analyzed for metabolites. Succinate derivatives can be identified as dimethyl esters in mass chromatograms due to their specific fragmentation pattern, e.g., m/z 114, 146, [M-73] as well as [M-31] and m/z 131, 145, [M-145], [M-60] as well as [M] for alkyl- and benzyl-succinates, respectively (for further details see Supplementary Material).

Bottom Line: In this work the metabolic activity of 11 bacterial strains during anaerobic growth with crude oil was investigated and compared with the metabolite patterns appearing during anaerobic growth with more than 40 different hydrocarbons supplied as binary mixtures.Furthermore, we demonstrate that anaerobic hydroxylation of alkylbenzenes does not only occur in denitrifiers but also in sulfate reducers.The outcomes of this study provide a basis for geochemically tracing such processes in natural habitats and contribute to an improved understanding of microbial activity in hydrocarbon-rich anoxic environments.

View Article: PubMed Central - PubMed

Affiliation: Organic Geochemistry, Chemistry of the Earth, Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences Potsdam, Germany.

ABSTRACT
Anaerobic metabolism of hydrocarbons proceeds either via addition to fumarate or by hydroxylation in various microorganisms, e.g., sulfate-reducing or denitrifying bacteria, which are specialized in utilizing n-alkanes or alkylbenzenes as growth substrates. General pathways for carbon assimilation and energy gain have been elucidated for a limited number of possible substrates. In this work the metabolic activity of 11 bacterial strains during anaerobic growth with crude oil was investigated and compared with the metabolite patterns appearing during anaerobic growth with more than 40 different hydrocarbons supplied as binary mixtures. We show that the range of co-metabolically formed alkyl- and arylalkyl-succinates is much broader in n-alkane than in alkylbenzene utilizers. The structures and stereochemistry of these products are resolved. Furthermore, we demonstrate that anaerobic hydroxylation of alkylbenzenes does not only occur in denitrifiers but also in sulfate reducers. We propose that these processes play a role in detoxification under conditions of solvent stress. The thermophilic sulfate-reducing strain TD3 is shown to produce n-alkylsuccinates, which are suggested not to derive from terminal activation of n-alkanes, but rather to represent intermediates of a metabolic pathway short-cutting fumarate regeneration by reverse action of succinate synthase. The outcomes of this study provide a basis for geochemically tracing such processes in natural habitats and contribute to an improved understanding of microbial activity in hydrocarbon-rich anoxic environments.

No MeSH data available.


Related in: MedlinePlus