TY - JOUR AB - The dynamics of microbial degradation of exogenous contaminants, n-hexadecane and its primary microbial oxidized metabolite, n-hexadecanoic (palmitic) acid, was studied for topsoils, under agricultural management and beech forest on the basis the changes in O-2 uptake, CO2 evolution and its associated carbon isotopic signature, the respiratory quotient (RQ) and the priming effect (PE) of substrates. Soil microbial communities in agricultural soil responded to the n-hexadecane addition more rapidly compared to those of forest soil, with lag-periods of about 23 +/- 10 and 68 +/- 13 hours, respectively. Insignificant difference in the lag-period duration was detected for agricultural (t(lag) = 30 +/- 13 h) and forest (t(lag) = 30 +/- 14 h) soils treated with n-hexadecanoic (palmitic) acid. These results demonstrate that the soil microbiota has different metabolic activities for using n-hexadecane as a reductive hydrocarbon and n-hexadecanoic acid as a partly oxidized hydrocarbon. The corresponding delta C-13 of respired CO2 after the addition of the hydrocarbon contaminants to soils indicates a shift in microbial activity towards the consumption of exogenous substrates with a more complete degradation of n-hexadecane in the agricultural soil, for which some initial contents of hydrocarbons are inherent. It is supposed that the observed deviation of RQ from theoretically calculated value under microbial substrate mineralization is determined by difference in the time (Delta t(i)) of registration of CO2 production and O-2 consumption. Positive priming effect (PE) of n-hexadecane and negative PE of n-hexadecanoic (palmitic) acid were detected in agricultural and forest soils. It is suggested that positive PE of n-hexadecane is conditioned by the induction of microbial enzymes that perform hydroxylation/oxygenation of stable SOM compounds mineralized by soil microbiota to CO2. The microbial metabolism coupled with oxidative decarboxylation of n-hexadecanoic acid is considered as one of the most probable causes of the revealed negative PE value. AU - Zyakun, A.* AU - Nii-Annang, S.* AU - Franke, G.* AU - Fischer, T.* AU - Buegger, F. AU - Dilly, O.* C1 - 7997 C2 - 29993 SP - 570-584 TI - Microbial activity and 13C/12C ratio as evidence of N-Hexadecane and N-Hexadecanoic acid biodegradation in agricultural and forest soils. JO - Geomicrobiol. J. VL - 29 IS - 6 PB - Taylor & Francis Inc. PY - 2012 SN - 0149-0451 ER - TY - JOUR AB - Three principally different mechanisms contribute to the wear-down process of mineral aggregates in sedimentary environments: (1) mechanical abrasion by forces of wind and water and by floating or saltating neighbouring grains, (2) chemical attack and dissolution by fluids, and (3) physical bioerosion and chemical biocorrosion. It is however, difficult to attribute the specific surface changes to specific environments and processes. Quartz sand grains from subaerial and subaquatic environments were analysed by atomic force microscopy (AFM) for traces of natural and experimental aeolian, aquatic and biological wear-down processes. Quantitative topographical parameters of surface alterations were extracted from topography data by non-linear methods derived from digital image analysis. These parameters were examined by multivariate statistic, yielding three well-distinguishable groups. Morphological surface alterations dominated by subaerial, subaquatic and by biological impact could be differentiated. The method may also be used for the detection of aeolian, subaquatic, and biological modification of sedimentary grains and rock surfaces in extraterrestrial environments, and for assessment of environmental damage on monuments and buildings. AU - Gorbushina, A.A.* AU - Kempe, A.* AU - Rodenacker, K. AU - Jütting, U. AU - Altermann, W.* AU - Stark, R.W.* AU - Heckl, W.M.* AU - Krumbein, W.E.* C1 - 5433 C2 - 28457 CY - Philadelphia, USA SP - 172-184 TI - Quantitative 3-dimensional image analysis of mineral surface modifications - chemical, mechanical and biological. JO - Geomicrobiol. J. VL - 28 IS - 2 PB - Taylor & Francis PY - 2011 SN - 0149-0451 ER - TY - JOUR AB - High-resolution depth-resolved monitoring was applied to groundwater and sediments samples in a tar oil contaminated aquifer. Today, it is not fully clear, whether groundwater-based lines of evidence are always sufficient to adequately assess natural attenuation (NA) potentials and processes going on in situ. Our data unveiled small-scale heterogeneities, steep physical-chemical and microbial gradients, as well as hot spots of contaminants and biodegradation in the supposedly homogeneous sandy aquifer. The comparison of basic geochemical data revealed a fairly good agreement between sediment and groundwater samples. Nevertheless, a comprehensive understanding of both BTEX and PAH distribution, as well as redox processes involving insoluble electron acceptors, i.e., iron reduction, clearly asks for consideration of both, sediment and groundwater analysis. A thin BTEX plume right below the groundwater table was visible only in groundwater, while significant amounts of PAHs were present in sediments from deeper zones of the aquifer. Indications for sulfate reduction as a dominant process involved in BTEX degradation were largely obtained from groundwater, while the role of iron reduction in degradation and possible sulfide oxidation at the capillary fringe and the upper BTEX plume fringe, as well as in deeper PAH-contaminated zones was evident from sediments. Moreover, sediment analyses were essential to meaningfully recover cell abundances, distribution, activity and composition of the bacterial community. Sediments harbored 97.7% of bacterial cells and displayed enzyme activities 5 to 6 orders of magnitude higher than groundwater samples. Bacterial community T-RFLP fingerprints revealed important distinctions, but also similarities in depth-resolved microbial community distribution in sediments and water. An apparently highly specialized degrader population was found to dominate the lower BTEX plume fringe. However, even though sediment data seemed to comprise most community information found also in groundwater, this relation did not apply vice versa. In summary, our results show that groundwater sampled at an appropriate scale may contain sufficient information to identify and localize dominant redox reactions, but clearly fails to unravel natural attenuation potentials. This clearly emphasizes the importance of both groundwater and sediment samples for truly assessing natural attenuation potentials and activities at organically contaminated aquifers. AU - Anneser, B. AU - Pilloni, G. AU - Bayer, A. AU - Lüders, T. AU - Griebler, C. AU - Einsiedl, F.* AU - Richters, L.* C1 - 1016 C2 - 27117 SP - 130-142 TI - High resolution analysis of contaminated aquifer sediments and Groundwater - what can be learned in terms of natural attenuation? JO - Geomicrobiol. J. VL - 27 IS - 2 PB - Taylor & Francis PY - 2010 SN - 0149-0451 ER - TY - JOUR AB - Recent studies indicated that nanoparticulate minerals in the environment exhibit a higher reactivity than their respective bulk materials. Lately, this has also been reported for microbial iron reduction using nanosized iron oxides as electron acceptors. However, these results have been obtained under small-scale, static batch conditions. The study presented here implies a flow regime within porous medium under low salt conditions providing information on the retention of nanosized iron oxide and the long-term sustainability of their reduction. Goethite, present as coating on quartz sand as a default electron acceptor, was reduced by Geobacter sulfurreducens and discharged as Fe2 + up to a maximum concentration of 0.6 mM in the column effluent, finally representing 10% of the supplied ferric iron in total. Adding ferrihydrite colloids via the influent to goethite-coated quartz sand led to partial adsorption of the colloids, but also to a high reactivity with a maximum Fe2 + discharge of 1.2 mM. In total, 1.4 mmol out of 2.6 mmol ferrihydrite colloids were reduced. Upon addition of ferrihydrite colloids to the influent of a parallel column containing quartz sand without goethite coatings, the maximum concentration of discharged Fe2 + accounted also for 1.2 mM, and 0.4 mmol out of 0.6 mmol ferrihydrite colloids were reduced in total. The column experiments demonstrated that ferrihydrite colloids are highly reactive and bioavailable for microbial reduction under approximated in situ conditions. AU - Bosch, J. AU - Fritzsche, A.* AU - Totsche, K.U.* AU - Meckenstock, R.U. C1 - 401 C2 - 27199 SP - 123-129 TI - Nanosized ferrihydrite colloids facilitate microbial iron reduction under flow conditions. JO - Geomicrobiol. J. VL - 27 IS - 2 PB - Taylor & Francis PY - 2010 SN - 0149-0451 ER -