title: Biodegradation of C7 and C8 iso-alkanes under methanogenic conditions.
abstract: Iso-alkanes comprise a substantial proportion of petroleum and refined products that impact the environment, but their fate is cryptic under methanogenic conditions. We investigated methanogenic biodegradation of C7 and C8 iso-alkanes found in naphtha, specifically 2-methylhexane, 3-methylhexane, 2-methylheptane, 4-methylheptane and 3-ethylhexane. These were incubated as a mixture or individually with enrichment cultures derived from oil sands tailings ponds that generate methane from naphtha components; substrate depletion and methane production were monitored for up to 663 days. 3-Methylhexane and 4-methylheptane were degraded both singly and in the mixture, whereas 2-methylhexane and 2-methylheptane resisted degradation as single substrates but were depleted in the iso-alkane mixture, suggesting co-metabolism. 3-Ethylhexane was degraded neither singly nor with co-substrates. Putative metabolites consistent with succinylated C7 and C8 were detected, suggesting activation by addition of iso-alkanes to fumarate and corresponding to detection of alkylsuccinate synthase-like genes. 454 pyrotag sequencing, cloning and terminal restriction fragment length polymorphism of 16S rRNA genes revealed predominance of a novel member of the family Peptococcaceae (order Clostridiales) and Archaea affiliated with Methanoregula and Methanosaeta. We report here isomer-specific metabolism of C7 -C8 iso-alkanes under methanogenic conditions and propose their activation by a novel Peptococcaceae via addition to fumarate.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9.
authors.forename: Nidal
authors.initials: N
authors.lastname: Abu Laban
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9.
authors.forename: Anh
authors.initials: A
authors.lastname: Dao
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Semple
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9.
authors.forename: Julia
authors.initials: J
authors.lastname: Foght
mesh_terms: D000473:Alkanes / Q000737:chemistry / Q000378:metabolism*; D001673:Biodegradation, Environmental; D002244:Carbon / Q000378:metabolism; D019605:Euryarchaeota / Q000235:genetics / Q000378:metabolism*; D008697:Methane / Q000378:metabolism; D061329:Oil and Gas Fields; D010459:Peptococcaceae / Q000235:genetics / Q000378:metabolism*; D010578:Petroleum / Q000378:metabolism*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D000473:Alkanes; D010578:Petroleum; D012336:RNA, Ribosomal, 16S; D002244:Carbon; C004544:naphtha; D008697:Methane