Depth-Resolved Quantification of Anaerobic Toluene Degraders and Aquifer Microbial Community Patterns in Distinct Redox Zones of a Tar Oil Contaminant Plume

Abstract

Microbial degradation is the only sustainable component of natural attenuation in contaminated groundwater environments, yet its controls, especially in anaerobic aquifers, are still poorly understood. Hence, putative spatial correlations between specific populations of key microbial players and the occurrence of respective degradation processes remain to be unraveled. We therefore characterized microbial community distribution across a high-resolution depth profile of a tar oil-impacted aquifer where benzene, toluene, ethylbenzene, and xylene (BTEX) degradation depends mainly on sulfate reduction. We conducted depthresolved terminal restriction fragment length polymorphism fingerprinting and quantitative PCR of bacterial 16S rRNA and benzylsuccinate synthase genes (bssA) to quantify the distribution of total microbiota and specific anaerobic toluene degraders. We show that a highly specialized degrader community of microbes related to known deltaproteobacterial iron and sulfate reducers (Geobacter and Desulfocapsa spp.), as well as clostridial fermenters (Sedimentibacter spp.), resides within the biogeochemical gradient zone underneath the highly contaminated plume core. This zone, where BTEX compounds and sulfate-an important electron acceptor-meet, also harbors a surprisingly high abundance of the yet-unidentified anaerobic toluene degraders carrying the previously detected F1-cluster bssA genes (C. Winderl, S. Schaefer, and T. Lueders, Environ. Microbiol. 9:1035-1046, 2007). Our data suggest that this biogeochemical gradient zone is a hot spot of anaerobic toluene degradation. These findings show that the distribution of specific aquifer microbiota and degradation processes in contaminated aquifers are tightly coupled, which may be of value for the assessment and prediction of natural attenuation based on intrinsic aquifer microbiota.

Effects of Forest Age on Soil Fungal Community in a Northern Temperate Ecosystem

“…The method is simple, rapid, has a high resolution and good repeatability, and produces quantitative results; with these advantages it has been widely used to study the diversity of a variety of microbial communities [11][12][13]. Since the application of molecular biological techniques overcomes the limitations of traditional methods based on culture, it provides a more accurate estimate of the richness and evenness on the level of genes and identifies variation in species, which provides a more objective insight in the community composition of fungi present in the environment.…”

DNA-SIP identifies sulfate-reducing Clostridia as important toluene degraders in tar-oil-contaminated aquifer sediment

“…From a total of 87 bacterial 16S rRNA gene clones, 3 were identified as chimeric and excluded from further analysis. Phylogenetic trees were reconstructed from sequence data as described (Winderl et al, 2007(Winderl et al, , 2008. All sequences generated in this study have been deposited with GenBank and can be found under the accession numbers GU133208-GU133309.…”

“…Cloning, sequencing and phylogenetic analysis Amplicons generated with the primer sets Ba27f (Weisburg et al, 1991)/907r (Muyzer et al, 1995) (same as for T-RFLP) and 7772f/8546r (Winderl et al, 2007) were cloned and sequenced (Winderl et al, 2007(Winderl et al, , 2008) from selected gradient fractions (one 'light' and one 'heavy' 16S rRNA gene library, as well as one bssA gene library from a the same 'heavy' fraction). Selected terminal restriction fragments (T-RFs) predicted in silico for representative clones were verified in vitro (see Table 1).…”

“…From each gradient, 10 DNA fractions were selected for bacterial 16S rRNA gene terminal restriction fragment length polymorphism (T-RFLP) fingerprinting. Fluorescent-labeled amplicons were generated as detailed elsewhere (Winderl et al, 2008). Electrophoresis of MspI-restricted fragments was carried out on an ABI 3730 DNA Analyzer (Applied Biosystems, Darmstadt, Germany), and data evaluation with the Gene Mapper 5.1 software, all as previously described (Lueders et al, 2006).…”

Effect of reclaimed water effluent on bacterial community structure in the Typha angustifolia L. rhizosphere soil of urbanized riverside wetland, China

“…In the upstream, 12 clones comprising two OTUs associated with heavy metal resistance from polluted sediment had high similarity with Thiobacillus sp., each OTU was respectively isolated from Hg polluted sediment and leachate sediment (Regier et al, 2012;Liu et al, 2011). In the downstream, one OTU of a total of 18 clones were highly similar to Hydrogenophilaceae from the anaerobic environment in tar oil contaminant plume (Winderl et al, 2008).…”