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The anaerobic degradation of gaseous, nonmethane alkanes - From in situ processes to microorganisms.

Musat F - Comput Struct Biotechnol J (2015)

Bottom Line: Other phylotypes involved in gaseous alkane degradation have been identified based on stable-isotope labeling and whole-cell hybridization.Under anoxic conditions, propane and n-butane are activated similar to the higher alkanes, by homolytic cleavage of the C-H bond of a subterminal carbon atom, and addition of the ensuing radical to fumarate, yielding methylalkylsuccinates.An additional mechanism of activation at the terminal carbon atoms was demonstrated for propane, which could in principle be employed also for the activation of ethane.

View Article: PubMed Central - PubMed

Affiliation: Helmholtz Centre for Environmental Research - UFZ, Permoserstr. 15, 04318 Leipzig, Germany.

ABSTRACT
The short chain, gaseous alkanes ethane, propane, n- and iso-butane are released in significant amounts into the atmosphere, where they contribute to tropospheric chemistry and ozone formation. Biodegradation of gaseous alkanes by aerobic microorganisms, mostly bacteria and fungi isolated from terrestrial environments, has been known for several decades. The first indications for short chain alkane anaerobic degradation were provided by geochemical studies of deep-sea environments around hydrocarbon seeps, and included the uncoupling of the sulfate-reduction and anaerobic oxidation of methane rates, the consumption of gaseous alkanes in anoxic sediments, or the enrichment in (13)C of gases in interstitial water vs. the source gas. Microorganisms able to degrade gaseous alkanes were recently obtained from deep-sea and terrestrial sediments around hydrocarbon seeps. Up to date, only sulfate-reducing pure or enriched cultures with ethane, propane and n-butane have been reported. The only pure culture presently available, strain BuS5, is affiliated to the Desulfosarcina-Desulfococcus cluster of the Deltaproteobacteria. Other phylotypes involved in gaseous alkane degradation have been identified based on stable-isotope labeling and whole-cell hybridization. Under anoxic conditions, propane and n-butane are activated similar to the higher alkanes, by homolytic cleavage of the C-H bond of a subterminal carbon atom, and addition of the ensuing radical to fumarate, yielding methylalkylsuccinates. An additional mechanism of activation at the terminal carbon atoms was demonstrated for propane, which could in principle be employed also for the activation of ethane.

No MeSH data available.


Related in: MedlinePlus

Proven and proposed mechanisms for the biochemical activation of gaseous alkanes under anoxic conditions, by addition to fumarate yielding alkylsuccinates. For ethane, activation by addition to fumarate (a) can be envisioned based on the finding of propane activation at a terminal carbon atom, and by the identification of ethylsuccinate in environmental samples. Propane is activated by addition to fumarate at both the subterminal and terminal carbon atoms (b), yielding isopropyl- and n-propylsuccinate, respectively, with a higher frequency of activation events at the secondary carbon atom. Butane is activated only at the subterminal carbon atom (c), yielding (1-methylpropylsuccinate).
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f0010: Proven and proposed mechanisms for the biochemical activation of gaseous alkanes under anoxic conditions, by addition to fumarate yielding alkylsuccinates. For ethane, activation by addition to fumarate (a) can be envisioned based on the finding of propane activation at a terminal carbon atom, and by the identification of ethylsuccinate in environmental samples. Propane is activated by addition to fumarate at both the subterminal and terminal carbon atoms (b), yielding isopropyl- and n-propylsuccinate, respectively, with a higher frequency of activation events at the secondary carbon atom. Butane is activated only at the subterminal carbon atom (c), yielding (1-methylpropylsuccinate).

Mentions: Up to now, most investigations on the mechanism of alkane activation under anoxic conditions have been focused on the degradation of medium and long-chain n-alkanes (> C6) [49]. With respect to gaseous alkanes, relatively recent metabolite analyses have shown that activation by addition to fumarate also plays an important role. In cultures of strain BuS5 and of propane-degrading enrichment cultures, isopropylsuccinate and (1-methylpropyl)succinate were identified as metabolites, indicating that propane and n-butane are activated by addition to fumarate at the secondary carbon atom (Fig. 2) [46,48]. In addition, n-propylsuccinate was identified in propane-degrading cultures, suggesting a second route of propane activation at the primary carbon atoms [46,48]. Although initially considered as a side reaction, this second pathway was further substantiated by incubations of strain BuS5 with position-specific deuterium-labeled propane. It was shown that the activation of propane at the primary carbon atoms is significant, accounting for an estimated 30% of the activation events, with the bulk of 70% of activation events occurring at the secondary carbon atom [71]. The activation of propane at the primary carbon atoms opens up the possibility of ethane activation by a similar mechanism, yielding ethylsuccinate (Fig. 2). Although up to now no metabolites have been reported from anaerobic ethane-degrading cultures, this hypothesis is supported by the finding of ethylsuccinate in crude oil processing facilities, crude oil production wells [42], oilfields [40], and coal beds [41].


The anaerobic degradation of gaseous, nonmethane alkanes - From in situ processes to microorganisms.

Musat F - Comput Struct Biotechnol J (2015)

Proven and proposed mechanisms for the biochemical activation of gaseous alkanes under anoxic conditions, by addition to fumarate yielding alkylsuccinates. For ethane, activation by addition to fumarate (a) can be envisioned based on the finding of propane activation at a terminal carbon atom, and by the identification of ethylsuccinate in environmental samples. Propane is activated by addition to fumarate at both the subterminal and terminal carbon atoms (b), yielding isopropyl- and n-propylsuccinate, respectively, with a higher frequency of activation events at the secondary carbon atom. Butane is activated only at the subterminal carbon atom (c), yielding (1-methylpropylsuccinate).
© Copyright Policy - CC BY
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4402382&req=5

f0010: Proven and proposed mechanisms for the biochemical activation of gaseous alkanes under anoxic conditions, by addition to fumarate yielding alkylsuccinates. For ethane, activation by addition to fumarate (a) can be envisioned based on the finding of propane activation at a terminal carbon atom, and by the identification of ethylsuccinate in environmental samples. Propane is activated by addition to fumarate at both the subterminal and terminal carbon atoms (b), yielding isopropyl- and n-propylsuccinate, respectively, with a higher frequency of activation events at the secondary carbon atom. Butane is activated only at the subterminal carbon atom (c), yielding (1-methylpropylsuccinate).
Mentions: Up to now, most investigations on the mechanism of alkane activation under anoxic conditions have been focused on the degradation of medium and long-chain n-alkanes (> C6) [49]. With respect to gaseous alkanes, relatively recent metabolite analyses have shown that activation by addition to fumarate also plays an important role. In cultures of strain BuS5 and of propane-degrading enrichment cultures, isopropylsuccinate and (1-methylpropyl)succinate were identified as metabolites, indicating that propane and n-butane are activated by addition to fumarate at the secondary carbon atom (Fig. 2) [46,48]. In addition, n-propylsuccinate was identified in propane-degrading cultures, suggesting a second route of propane activation at the primary carbon atoms [46,48]. Although initially considered as a side reaction, this second pathway was further substantiated by incubations of strain BuS5 with position-specific deuterium-labeled propane. It was shown that the activation of propane at the primary carbon atoms is significant, accounting for an estimated 30% of the activation events, with the bulk of 70% of activation events occurring at the secondary carbon atom [71]. The activation of propane at the primary carbon atoms opens up the possibility of ethane activation by a similar mechanism, yielding ethylsuccinate (Fig. 2). Although up to now no metabolites have been reported from anaerobic ethane-degrading cultures, this hypothesis is supported by the finding of ethylsuccinate in crude oil processing facilities, crude oil production wells [42], oilfields [40], and coal beds [41].

Bottom Line: Other phylotypes involved in gaseous alkane degradation have been identified based on stable-isotope labeling and whole-cell hybridization.Under anoxic conditions, propane and n-butane are activated similar to the higher alkanes, by homolytic cleavage of the C-H bond of a subterminal carbon atom, and addition of the ensuing radical to fumarate, yielding methylalkylsuccinates.An additional mechanism of activation at the terminal carbon atoms was demonstrated for propane, which could in principle be employed also for the activation of ethane.

View Article: PubMed Central - PubMed

Affiliation: Helmholtz Centre for Environmental Research - UFZ, Permoserstr. 15, 04318 Leipzig, Germany.

ABSTRACT
The short chain, gaseous alkanes ethane, propane, n- and iso-butane are released in significant amounts into the atmosphere, where they contribute to tropospheric chemistry and ozone formation. Biodegradation of gaseous alkanes by aerobic microorganisms, mostly bacteria and fungi isolated from terrestrial environments, has been known for several decades. The first indications for short chain alkane anaerobic degradation were provided by geochemical studies of deep-sea environments around hydrocarbon seeps, and included the uncoupling of the sulfate-reduction and anaerobic oxidation of methane rates, the consumption of gaseous alkanes in anoxic sediments, or the enrichment in (13)C of gases in interstitial water vs. the source gas. Microorganisms able to degrade gaseous alkanes were recently obtained from deep-sea and terrestrial sediments around hydrocarbon seeps. Up to date, only sulfate-reducing pure or enriched cultures with ethane, propane and n-butane have been reported. The only pure culture presently available, strain BuS5, is affiliated to the Desulfosarcina-Desulfococcus cluster of the Deltaproteobacteria. Other phylotypes involved in gaseous alkane degradation have been identified based on stable-isotope labeling and whole-cell hybridization. Under anoxic conditions, propane and n-butane are activated similar to the higher alkanes, by homolytic cleavage of the C-H bond of a subterminal carbon atom, and addition of the ensuing radical to fumarate, yielding methylalkylsuccinates. An additional mechanism of activation at the terminal carbon atoms was demonstrated for propane, which could in principle be employed also for the activation of ethane.

No MeSH data available.


Related in: MedlinePlus