title: DNA-SIP identifies sulfate-reducing Clostridia as important toluene degraders in tar-oil-contaminated aquifer sediment.
abstract: Global groundwater resources are constantly challenged by a multitude of contaminants such as aromatic hydrocarbons. Especially in anaerobic habitats, a large diversity of unrecognized microbial populations may be responsible for their degradation. Still, our present understanding of the respective microbiota and their ecophysiology is almost exclusively based on a small number of cultured organisms, mostly within the Proteobacteria. Here, by DNA-based stable isotope probing (SIP), we directly identified the most active sulfate-reducing toluene degraders in a diverse sedimentary microbial community originating from a tar-oil-contaminated aquifer at a former coal gasification plant. On incubation of fresh sediments with (13)C(7)-toluene, the production of both sulfide and (13)CO(2) was clearly coupled to the (13)C-labeling of DNA of microbes related to Desulfosporosinus spp. within the Peptococcaceae (Clostridia). The screening of labeled DNA fractions also suggested a novel benzylsuccinate synthase alpha-subunit (bssA) sequence type previously only detected in the environment to be tentatively affiliated with these degraders. However, carbon flow from the contaminant into degrader DNA was only ∼50%, pointing toward high ratios of heterotrophic CO(2)-fixation during assimilation of acetyl-CoA originating from the contaminant by these degraders. These findings demonstrate that the importance of non-proteobacterial populations in anaerobic aromatics degradation, as well as their specific ecophysiology in the subsurface may still be largely ungrasped.
authors.affiliation: Institute of Groundwater Ecology, Helmholtz Zentrum München-German Research Centre for Environmental Health, Neuherberg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Winderl
authors.forename: Holger
authors.initials: H
authors.lastname: Penning
authors.forename: Frederick von
authors.initials: Fv
authors.lastname: Netzer
authors.forename: Rainer U
authors.initials: RU
authors.lastname: Meckenstock
authors.forename: Tillmann
authors.initials: T
authors.lastname: Lueders
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D002245:Carbon Dioxide / Q000378:metabolism; D019755:Carbon-Carbon Lyases / Q000235:genetics; D004247:DNA / Q000235:genetics* / Q000302:isolation & purification*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004783:Environmental Microbiology; D004785:Environmental Pollutants / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010459:Peptococcaceae / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D010578:Petroleum / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013431:Sulfates / Q000378:metabolism*; D013638:Tars / Q000378:metabolism; D014050:Toluene / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004785:Environmental Pollutants; D010578:Petroleum; D013431:Sulfates; D013638:Tars; D002245:Carbon Dioxide; D014050:Toluene; D004247:DNA; D019755:Carbon-Carbon Lyases; C114354:benzylsuccinate synthase