Limits...
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.


Related in: MedlinePlus

Stereochemistry of alkyl-/arylalkyl-succinates formed by different strains. Mas, methylalkylsuccinate synthase; Bss, benzylsuccinate synthase; R = H, alkyl; n = 1…8.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4561516&req=5

Figure 4: Stereochemistry of alkyl-/arylalkyl-succinates formed by different strains. Mas, methylalkylsuccinate synthase; Bss, benzylsuccinate synthase; R = H, alkyl; n = 1…8.

Mentions: All investigated alkylbenzene-utilizing strains formed exclusively (R)-2-benzylsuccinate from toluene, which was confirmed by comparison with a standard. All other succinate derivatives detected in these cultures consisted of exclusively one stereoisomer. As in all cases the later eluting isomer was found, we propose that always the (R)-stereoisomer of the succinate is formed (Figure 4). In contrast, the alkyl-/arylalkyl-succinates formed by n-alkane utilizers were generally present as two stereoisomers (Figure 4). In case of n-hexane-derived (1-methylpentyl)succinate, strains HxN1, OcN1, and TD3 formed the (2R,1′R)- as well as the (2S,1′R)-isomer, as confirmed by standard comparison. These are the first and the last eluting of the four possible isomers (Jarling et al., 2012). Likewise, in the cases of (1-phenylethyl)succinate (ethylbenzene-derived) and (1-methyl-4-phenylbutyl)succinate (n-pentylbenzene-derived), only the first and last eluting isomers were formed. From equidistant GC retention times we infer that the same is true for all other succinate derivatives with two stereocenters and suggest that they were also present as the epimers at carbon atom 2. Succinate derivatives with only a single stereocenter located in the succinate moiety were always found as mixtures of both enantiomers.


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)

Stereochemistry of alkyl-/arylalkyl-succinates formed by different strains. Mas, methylalkylsuccinate synthase; Bss, benzylsuccinate synthase; R = H, alkyl; n = 1…8.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 4: Stereochemistry of alkyl-/arylalkyl-succinates formed by different strains. Mas, methylalkylsuccinate synthase; Bss, benzylsuccinate synthase; R = H, alkyl; n = 1…8.
Mentions: All investigated alkylbenzene-utilizing strains formed exclusively (R)-2-benzylsuccinate from toluene, which was confirmed by comparison with a standard. All other succinate derivatives detected in these cultures consisted of exclusively one stereoisomer. As in all cases the later eluting isomer was found, we propose that always the (R)-stereoisomer of the succinate is formed (Figure 4). In contrast, the alkyl-/arylalkyl-succinates formed by n-alkane utilizers were generally present as two stereoisomers (Figure 4). In case of n-hexane-derived (1-methylpentyl)succinate, strains HxN1, OcN1, and TD3 formed the (2R,1′R)- as well as the (2S,1′R)-isomer, as confirmed by standard comparison. These are the first and the last eluting of the four possible isomers (Jarling et al., 2012). Likewise, in the cases of (1-phenylethyl)succinate (ethylbenzene-derived) and (1-methyl-4-phenylbutyl)succinate (n-pentylbenzene-derived), only the first and last eluting isomers were formed. From equidistant GC retention times we infer that the same is true for all other succinate derivatives with two stereocenters and suggest that they were also present as the epimers at carbon atom 2. Succinate derivatives with only a single stereocenter located in the succinate moiety were always found as mixtures of both enantiomers.

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