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C. Monard F. Martin-Laurent C. Vecchiato A.J. Francez P. Vandenkoornhuyse F. Binet 《Soil biology & biochemistry》2008,40(9):2253-2259
Earthworms, because they change soil physical and chemical properties, are efficient engineers that act on soil microbial community and activity. Thus they may drive pollutant biodegradation in soil such as atrazine mineralization. We hypothesized that earthworms modify the abundance of indigenous soil bacteria and the fate and activity of atrazine-degraders in the soil they engineer by bioturbation. Two bacterial strains were used as bioaugmentation agents: Pseudomonas sp. ADP and Chelatobacter heintzii, which have acquired the capacity to metabolize atrazine by carrying plasmidic atz A, B, C, D, E, F and atzA, B, C, trzD genes, respectively. We analyzed the interactions between earthworms (Lumbricus terrestris) and the indigenous and atrazine-degrading (indigenous and inoculated) bacterial communities by quantifying the 16S rRNA and the atzA gene sequence copies numbers, respectively, in different earthworm microsites. The kinetics of atrazine mineralization were measured to link the bacterial community changes with the degradation function. Digestion by earthworms significantly impacted the number of indigenous bacteria and atrazine mineralization in bioaugmented soils. Regarding the fate of the two atrazine-degraders tested, Pseudomonas sp. strain ADP survived better within the 10 days of experiment than C. heintzii in the bulk soil but the surviving fraction of C. heintzii was still metabolically active and able to mineralize atrazine. A positive “burrow-lining” effect on the atzA sequence copies number was observed in soil whether bioaugmented with C. heintzii or not (i.e. native indigenous atzA) thereby indicating that burrow-linings form a specific ‘hot spot’ for atrazine-degraders. The present study is the first to report the role of earthworms in selecting native catabolic key-genes in soil (indigenous atzA). This catabolic gene selection through earthworm soil bioturbation could be important in sustaining the degradation (detoxification) function of soil. 相似文献
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Rebekka R.E. Artz Stephen J. Chapman A.H. Jean Robertson Jacqueline M. Potts Fatima Laggoun-Défarge Sébastien Gogo Laure Comont Jean-Robert Disnar Andre-Jean Francez 《Soil biology & biochemistry》2008,40(2):515-527
Vegetational changes during the restoration of cutover peatlands leave a legacy in terms of the organic matter quality of the newly formed peat. Current efforts to restore peatlands at a large scale therefore require low cost and high throughput techniques to monitor the evolution of organic matter. In this study, we assessed the merits of using Fourier transform infrared (FTIR) spectra to predict the organic matter composition in peat samples at various stages of peatland regeneration from five European countries. Using predictive partial least squares (PLS) analyses, we were able to reconstruct peat C:N ratio and carbohydrate signatures with reasonable accuracy, but not the micromorphological composition of vegetation remains. Despite utilising different size fractions, both carbohydrate (<200 μm fraction) and FTIR (bulk soil) analyses report on the composition of plant cell wall constituents in the peat and therefore essentially reveal the composition of the parent vegetational material. The accuracy of the FTIR-based PLS models for C:N ratios and carbohydrate signatures was adequate to allow for their use as initial screening tools in the evaluation of the present and future organic matter composition of peat during monitoring of restoration efforts. 相似文献
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The Bois-des-Bel Sphagnum peatland (Rivière du Loup, QC) was restored in 1999 after 20 years of abandonment. Restoration work included not only the blockage of drainage ditches, but also the reintroduction of plant material including Sphagnum remains. Following restoration, the physicochemical and microbial characteristics (biomass, activity and composition) of the peat were analysed. The goal was to investigate the functional status of the restored ecosystem. The high N:P (>20) and N:K (>15) ratios indicated possible K and P deficiencies in the restored and the cutover sites, which is mainly associated with the intense leaching and the high degree of decomposition of the peat in these sites. The concentrations of , P and K in the top layer of the restored site were closer to those of the natural site, which indicated a possible effect of restoration on the physicochemistry of the restored site. Microbial biomass values derived from the FE technique followed a gradient natural>restored>cutover through the profile, which was not the case with the SIR technique. Values from SIR varied overall between 0.19 and 4.88 mg C g−1 and were significantly higher in the natural site. The natural peatland site had significantly (P<0.05) greater cumulative C-CO2 production (surface aerobic: 4.5-8.7 μg C-CO2 g−1 h−1). The poor organic matter quality was the main explanation for the low respiration rates of the surface layer in the restored and the cutover site. All CO2 respiration data were plotted against time and the resulting curves were successfully fitted to a global kinetic model. Methane production was detected at low but measurable rates in the natural and the restored samples, but not in the cutover peat. Overall, the results confirmed the existence of a lag between the positive response of vegetation to restoration and that of the microbial compartment. This study also pointed out that some physicochemical dysfunctions remained even after three growing seasons following restoration in the subsurface horizons studied. 相似文献
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