title: Biodegradation of low-molecular-weight alkanes under mesophilic, sulfate-reducing conditions: metabolic intermediates and community patterns.
abstract: We evaluated the ability of the native microbiota in a low-temperature, sulfidic natural hydrocarbon seep (Zodletone) to metabolize short-chain hydrocarbons. n-Propane and n-pentane were metabolized under sulfate-reducing conditions in initial enrichments and in sediment-free subcultures. Carbon isotope analysis of residual propane in active enrichments showed that propane became enriched in (13)C by 6.7 (+/-2.0) per thousand, indicating a biological mechanism for propane loss. The detection of n-propylsuccinic and isopropylsuccinic acids in active propane-degrading enrichments provided evidence for anaerobic biodegradation via a fumarate addition pathway. A eubacterial 16S rRNA gene survey of sediment-free enrichments showed that the majority of the sequenced clones were phylogenetically affiliated within the Deltaproteobacteria. Such sequences were most closely affiliated with clones retrieved from hydrocarbon-impacted marine ecosystems, volatile fatty acid metabolizers, hydrogen users, and with a novel Deltaproteobacterial lineage. Other cloned sequences were affiliated with the Firmicutes and Chloroflexi phyla. The sequenced clones were only distantly (<95%) related to other reported low-molecular-weight alkane-degrading sulfate-reducing populations. This work documents the potential for anaerobic short-chain n-alkane metabolism for the first time in a terrestrial environment, provides evidence for a fumarate addition mechanism for n-propane activation under these conditions, and reveals microbial community members present in such enrichments.
authors.affiliation: Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK 74074, USA.
authors.forename: Kristen N
authors.initials: KN
authors.lastname: Savage
authors.forename: Lee R
authors.initials: LR
authors.lastname: Krumholz
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Gieg
authors.forename: Victoria A
authors.initials: VA
authors.lastname: Parisi
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Suflita
authors.forename: Jon
authors.initials: J
authors.lastname: Allen
authors.forename: R Paul
authors.initials: RP
authors.lastname: Philp
authors.forename: Mostafa S
authors.initials: MS
authors.lastname: Elshahed
mesh_terms: D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D002247:Carbon Isotopes / Q000032:analysis; D004269:DNA, Bacterial / Q000235:genetics; D020564:Deltaproteobacteria / Q000235:genetics / Q000378:metabolism; D017753:Ecosystem; D019015:Geologic Sediments / Q000382:microbiology; D010420:Pentanes / Q000378:metabolism*; D011407:Propane / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013431:Sulfates / Q000378:metabolism*; D016999:Sulfur-Reducing Bacteria / Q000235:genetics / Q000378:metabolism*; D014871:Water Microbiology
chemical_list: D002247:Carbon Isotopes; D004269:DNA, Bacterial; D010420:Pentanes; D012336:RNA, Ribosomal, 16S; D013431:Sulfates; C033353:pentane; D011407:Propane