Sulfate-reducing bacterial community response to carbon source amendments in contaminated aquifer microcosms

Isotopic labeling of biomarker molecules is a technique applied to link microbial community structure with activity. Previously, we successfully labeled phospholipid fatty acids (PLFA) of suspended nitrate-reducing bacteria in an aquifer. However, the application of the method to low energy-yielding processes such as sulfate reduction, and extension of the analysis to attached communities remained to be studied. To test the feasibility of the latter application, an anoxic test solution of 500 l of groundwater with addition of 0.5 mM Br- as a conservative tracer, 1.1 mM SO4(2-), and 2.0 mM [2-13C]acetate was injected in the transition zone of a petroleum hydrocarbon-contaminated aquifer where sulfate-reducing and methanogenic conditions prevailed. Thousand liters of test solution/groundwater mixture were extracted in a stepwise fashion after 2-46 h incubation. Computed apparent first-order rate coefficients were 0.31+/-0.04 day(-1) for acetate and 0.34+/-0.05 day(-1) for SO4(2-) consumption. The delta13C increased from -71.03 per thousand to +3352.50 per thousand in CH4 and from -16.15 per thousand to +32.13 per thousand in dissolved inorganic carbon (DIC). A mass balance suggested that 43% of the acetate-derived (13)C appeared in DIC and 57% appeared in CH4. Thus, acetate oxidation coupled to sulfate reduction and acetoclastic methanogenesis occurred simultaneously. The delta13C of PLFA increased on average by 27 per thousand in groundwater samples and 4 per thousand in sediment samples. Hence, both suspended and attached communities actively degraded acetate. The PLFA labeling patterns and fluorescent in situ hybridization (FISH) analyses of sediment and groundwater samples suggested that the main sulfate-reducing bacteria degrading the acetate were Desulfotomaculum acetoxidans and Desulfobacter sp. in groundwater, and D. acetoxidans in sediment.

Section: Incorporation Of 13 C Into Plfacontrasting

confidence: 68%

Field-scale isotopic labeling of phospholipid fatty acids from acetate-degrading sulfate-reducing bacteria

Pombo

Kleikemper

Schroth

et al. 2005

“…Kasai et al ., 2006) or aquifer material (e.g. Beller et al ., 1996; Kleikemper et al ., 2002) as inoculum for laboratory microcosms. In the present study, a specific field‐based microcosm system facilitating the enrichment of indigenous groundwater microorganisms on site, as well as the subsequent analysis of their community structure and carbon assimilation patterns have been applied (Peacock et al ., 2004; Geyer et al ., 2005; Kästner et al ., 2006).…”

Section: Introductionmentioning

confidence: 99%

Enrichment and characterization ofâ a sulfate-reducing toluene-degrading microbial consortium by combiningin situmicrocosms and stable isotope probing techniques

Bombach¹,

Chatzinotas²,

Neu³

et al. 2010

A toluene-degrading microbial consortium was enriched directly in a BTEX-contaminated aquifer under sulfate-reducing conditions using in situ microcosms consisting of toluene-loaded activated carbon pellets. Degradation of toluene and concomitant sulfide production by the consortium was subsequently demonstrated in laboratory microcosms. The consortium was physiologically and phylogenetically characterized by isotope tracer experiments using nonlabeled toluene, [(13)C]-alpha-toluene or [(13)C(7)]-toluene as growth substrates. Cells incubated with [(13)C]-alpha-toluene or [(13)C(7)]-toluene incorporated 8-15 at.%(13)C and 51-57 at.%(13)C into total lipid fatty acids, respectively, indicating a lower specific incorporation of (13)C from [(13)C(7)]-toluene. In order to identify the toluene-assimilating bacteria, the incorporation of carbon from both [(13)C]-alpha-toluene and [(13)C(7)]-toluene into rRNA was analyzed by stable isotope probing. Time and buoyant density-resolved 16S rRNA gene-based terminal restriction fragment length polymorphism profiles, combined with cloning and sequencing, revealed that an uncultured bacterium (99% sequence similarity) related to the genus Desulfocapsa was the main toluene-degrading organism in the consortium. The ratio of the respective terminal restriction fragments changed over time, indicating trophic interactions within this consortium.

“…Desulfobulbus appear to be ubiquitous in anoxic sediments, consistently making up 1–3% of the total sulphate‐reducing bacteria (SRB) community in marine, estuarine and freshwater sediments (Purdy et al ., 2002). Desulfobulbus are SRB that oxidize propionate to acetate (Widdel & Pfennig, 1982; Fowler et al ., 1986; King et al ., 2000; Kleikemper et al ., 2002). Given its ubiquity, it may be the major propionate‐utilizing bacteria in many anoxic environments.…”

Section: Introductionmentioning

confidence: 99%

Genotypic distribution of an indigenous model microorganism along an estuarine gradient

Hawkins

Purdy

2007

Using the genus Desulfobulbus as an indigenous model, microbial distribution along an estuarine gradient was investigated. Denaturing gradient gel electrophoresis analysis indicated a sequential change in Desulfobulbus genotypes along the estuary with marine, brackish and freshwater genotypes detected. This differential distribution was significantly correlated with porewater concentrations of chloride, sulphate and nitrate. Temporal analysis indicated that there was a shift in the whole Desulfobulbus community towards to marine end of the estuary by the end of the winter compared with the late summer. This distribution pattern is similar to those seen with other estuarine organisms and, given the correlation with chloride and sulphate, is indicative of classic niche separation within this genus driven by gross environmental factors such as salinity. These results will help in developing a truly ecological description of microbial biodiversity.