title: Stable isotopic studies of n-alkane metabolism by a sulfate-reducing bacterial enrichment culture.
abstract: Gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy were used to study the metabolism of deuterated n-alkanes (C6 to C12) and 1-13C-labeled n-hexane by a highly enriched sulfate-reducing bacterial culture. All substrates were activated via fumarate addition to form the corresponding alkylsuccinic acid derivatives as transient metabolites. Formation of d14-hexylsuccinic acid in cell extracts from exogenously added, fully deuterated n-hexane confirmed that this reaction was the initial step in anaerobic alkane metabolism. Analysis of resting cell suspensions amended with 1-13C-labeled n-hexane confirmed that addition of the fumarate occurred at the C-2 carbon of the parent substrate. Subsequent metabolism of hexylsuccinic acid resulted in the formation of 4-methyloctanoic acid, and 3-hydroxy-4-methyloctanoic acid was tentatively identified. We also found that 13C nuclei from 1-13C-labeled n-hexane became incorporated into the succinyl portion of the initial metabolite in a manner that indicated that 13C-labeled fumarate was formed and recycled during alkane metabolism. Collectively, the findings obtained with a sulfate-reducing culture using isotopically labeled alkanes augment and support the previously proposed pathway (H. Wilkes, R. Rabus, T. Fischer, A. Armstroff, A. Behrends, and F. Widdel, Arch. Microbiol. 177:235-243, 2002) for metabolism of deuterated n-hexane by a denitrifying bacterium.
authors.affiliation: Department of Botany & Microbiology, The University of Oklahoma, Norman, OK 73019, USA.
authors.forename: Irene A
authors.initials: IA
authors.lastname: Davidova
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Gieg
authors.forename: Mark
authors.initials: M
authors.lastname: Nanny
authors.forename: Kevin G
authors.initials: KG
authors.lastname: Kropp
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Suflita
mesh_terms: D000473:Alkanes / Q000378:metabolism*; D001419:Bacteria / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D002247:Carbon Isotopes; D002264:Carboxylic Acids / Q000378:metabolism; D003470:Culture Media; D008401:Gas Chromatography-Mass Spectrometry; D006586:Hexanes / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D012722:Sewage / Q000382:microbiology*; D013431:Sulfates / Q000378:metabolism*
chemical_list: D000473:Alkanes; D002247:Carbon Isotopes; D002264:Carboxylic Acids; D003470:Culture Media; D006586:Hexanes; D012722:Sewage; D013431:Sulfates