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71.
The effect of sulfide on nitrate reduction and methanogenesis was investigated in two mixed, mesophilic (35 degrees C) methanogenic cultures: sulfide-free and sulfide-acclimated (67 mg S/L total sulfide). A mixture of dextrin/peptone served as the carbon/electron donor source for the two stock cultures, as well as in all assays reported here. The sulfide-free enriched culture was amended with both nitrate (75-350 mg N/L) and sulfide (10-100 mg S/L). Denitrification was the predominant pathway at all sulfide levels tested and methanogenesis did not recover in any of the sulfide- and nitrate-amended cultures, except in the 10 mg S/L culture. Accumulation of denitrification intermediates such as NO and N(2)O took place, which irreversibly inhibited the methanogens and resulted in the complete cessation of methane production. In contrast, conversion of nitrate to nitrite and then to ammonia via dissimilatory nitrate reduction to ammonia (DNRA) prevented the accumulation of denitrification intermediates and led to the recovery of methanogenesis in the nitrate-amended, sulfide-acclimated, mixed methanogenic culture. The effect of the COD/N value on nitrate reduction was assessed with the sulfide-acclimated, methanogenic culture at COD/N values of 10, 20, and 60. As the COD/N value increased, the fraction of nitrate reduced through DNRA also increased. The results of this study have significant implications relative to the combined anaerobic treatment of carbon-, nitrogen-, and/or sulfur-bearing wastes. 相似文献
72.
Chansotheary Dang Ember M. Morrissey Scott C. Neubauer Rima B. Franklin 《Global Change Biology》2019,25(2):549-561
Sea level rise and changes in precipitation can cause saltwater intrusion into historically freshwater wetlands, leading to shifts in microbial metabolism that alter greenhouse gas emissions and soil carbon sequestration. Saltwater intrusion modifies soil physicochemistry and can immediately affect microbial metabolism, but further alterations to biogeochemical processing can occur over time as microbial communities adapt to the changed environmental conditions. To assess temporal changes in microbial community composition and biogeochemical activity due to saltwater intrusion, soil cores were transplanted from a tidal freshwater marsh to a downstream mesohaline marsh and periodically sampled over 1 year. This experimental saltwater intrusion produced immediate changes in carbon mineralization rates, whereas shifts in the community composition developed more gradually. Salinity affected the composition of the prokaryotic community but did not exert a strong influence on the community composition of fungi. After only 1 week of saltwater exposure, carbon dioxide production doubled and methane production decreased by three orders of magnitude. By 1 month, carbon dioxide production in the transplant was comparable to the saltwater controls. Over time, we observed a partial recovery in methane production which strongly correlated with an increase in the relative abundance of three orders of hydrogenotrophic methanogens. Taken together, our results suggest that ecosystem responses to saltwater intrusion are dynamic over time as complex interactions develop between microbial communities and the soil organic carbon pool. The gradual changes in microbial community structure we observed suggest that previously freshwater wetlands may not experience an equilibration of ecosystem function until long after initial saltwater intrusion. Our results suggest that during this transitional period, likely lasting years to decades, these ecosystems may exhibit enhanced greenhouse gas production through greater soil respiration and continued methanogenesis. 相似文献
73.
Isolation and characterization of Methanoculleus receptaculi sp. nov. from Shengli oil field, China 总被引:1,自引:0,他引:1
Three strictly anaerobic, thermophilic methanogens (ZC-2T, ZC-3 and ZC-6) were isolated from Shengli oil field, China. The 16S rRNA gene sequences of the three strains were nearly identical, possessing > 99.8% sequence similarity. They also possessed high sequence similarity, 97.4%, to Methanoculleus palmolei strain INSLUZ(T) (97.4% and 97.5%, respectively), indicating that they represented a novel species within the genus Methanoculleus. Cells of strain ZC-2T were nonmotile cocci, 0.8-1.7 microm in diameter, and always occurred singly or in pairs. The three strains used H2/CO2 or sodium formate as substrates for methanogenesis but not sodium acetate, trimethylamine, monomethylamine, ethanol, dimethyl sulfide, isopropanol, isobutanol, butan-2-ol or H2/CO. Optimum growth of strain ZC-2T occurred in the presence of 0.2 M NaCl, pH 7.5-7.8 and temperature 50-55 degrees C with a specific growth rate of 0.084 h(-1). The mol% G+C content of the genomic DNA was 55.2 mol%. Based on these phenotypic and phylogenetic characteristics, strains ZC-2T, ZC-3 and ZC-6 are proposed to represent a novel species in the genus Methanoculleus and named Methanoculleus receptaculi sp. nov. The type strain is ZC-2T (CGMCC 1.5087T=DSM 18860T). 相似文献
74.
What stabilizes the unique Ni(I) state of the active form of coenzyme F(430) and of methylcoenzyme M reductase, the enzyme responsible for the last methane-evolving step of biological methanogenesis? A survey of F(430) model compounds suggests that the monoanionic nature of the F(430) ligand goes a long way toward explaining the stability of Ni(I) F(430). Second, nature appears to have manipulated the stereochemistry of the macrocycle, particularly that of the 12- and 13- substituents, so that the cofactor is sterically constrained against ruffling and forced to adopt a relatively planar conformation with long Ni--N distances. Third, the carbonyl substituent at the 15-meso position electronically stabilizes the Ni(I) state of the cofactor. With regard to the mechanism of methylcoenzyme M reductase, the most reasonable mechanism, in our opinion, involves a Ni(I)-mediated homolytic cleavage of the S--CH(3) bond in methylcoenzyme M, followed immediately by the quenching of the methyl radical by coenzyme B (a thiol) to produce methane. 相似文献
75.
76.
Yu Jiang Kees Jan van Groenigen Shan Huang Bruce A. Hungate Chris van Kessel Shuijin Hu Jun Zhang Lianhai Wu Xiaojun Yan Lili Wang Jin Chen Xiaoning Hang Yi Zhang William R. Horwath Rongzhong Ye Bruce A. Linquist Zhenwei Song Chengyan Zheng Aixing Deng Weijian Zhang 《Global Change Biology》2017,23(11):4728-4738
Breeding high‐yielding rice cultivars through increasing biomass is a key strategy to meet rising global food demands. Yet, increasing rice growth can stimulate methane (CH4) emissions, exacerbating global climate change, as rice cultivation is a major source of this powerful greenhouse gas. Here, we show in a series of experiments that high‐yielding rice cultivars actually reduce CH4 emissions from typical paddy soils. Averaged across 33 rice cultivars, a biomass increase of 10% resulted in a 10.3% decrease in CH4 emissions in a soil with a high carbon (C) content. Compared to a low‐yielding cultivar, a high‐yielding cultivar significantly increased root porosity and the abundance of methane‐consuming microorganisms, suggesting that the larger and more porous root systems of high‐yielding cultivars facilitated CH4 oxidation by promoting O2 transport to soils. Our results were further supported by a meta‐analysis, showing that high‐yielding rice cultivars strongly decrease CH4 emissions from paddy soils with high organic C contents. Based on our results, increasing rice biomass by 10% could reduce annual CH4 emissions from Chinese rice agriculture by 7.1%. Our findings suggest that modern rice breeding strategies for high‐yielding cultivars can substantially mitigate paddy CH4 emission in China and other rice growing regions. 相似文献
77.
Influence of Ni, Co, Fe, and Na additions on methane production in Sphagnum-dominated Northern American peatlands 总被引:2,自引:0,他引:2
Although Sphagnum (moss)-dominated, northern peatlandecosystems harbor methane (CH4)-producing microorganisms(methanogens) and are a significant source of atmosphericCH4, rates of CH4 production vary widely amongdifferent systems. Very little work has been done to examine whetherconcentrations of cations and metal elements may account for thevariability. We examined rates of CH4 production in peat fromfive geographically and functionally disparateSphagnum-dominated peatlands by incubating peat samples invitro with and without additions of trace metals (Fe, Ni, Co) andbase cations (Ca, Li, Na). In peat from the most mineral poor sites, theaddition of metals and Na enhanced CH4 production beyond thatobserved in controls. The same treatments in mineral rich sites yieldedno effect or an inhibition of CH4 production. None of thetreatments affected anaerobic respiration, measured as CO2production, in the in vitro incubations of peat, except addedcitrate, suggesting that methanogens, and not the entire anaerobiccommunity, can be limited by the availability of metal elements andcations. 相似文献
78.
L. Hellings K. Van den Driessche W. Baeyens E. Keppens F. Dehairs 《Biogeochemistry》2000,51(2):141-160
Processes affecting the concentration and isotopiccomposition of dissolved inorganic carbon (DIC) wereinvestigated in pore waters of two freshwaterintertidal areas of the Scheldt Estuary, Belgium. Porewater 13CDIC values from marshes andmudflats varied from –27 to +13.4, these very largevariations reflect the contribution of differentcarbon sources to the DIC pool.In pore waters of the upper mudflat, river water DICand dissolution of calcite contribute to a lesserextent (10% and 16% respectively) to the total DICpool. Results indicate that inorganic carbon added tothe pore water of the mudflats has a 13Cvalue of +20.3 in May 1998. These strongly enriched13CDIC values suggest that the majorcontribution (up to three-quarters) to total DIC isCO2 derived from methanogenesis.In pore waters of the marshes, CO2 derived fromorganic matter degradation (–27.5) and river DIC(–11.5 to –16.1) are the major sources of inorganiccarbon contribution to the total DIC pool. In porewaters from a marsh site colonised by willow trees,the contribution from CO2 derived from organicmatter degradation is larger than in pore waters froman area with only reed vegetation. In the latter caseriver water DIC is the major source of pore waterDIC. 相似文献
79.
80.
Ineke Scholten-Koerselman Frank Houwaard Paul Janssen Alexander J. B. Zehnder 《Antonie van Leeuwenhoek》1986,52(6):543-554
As part of a study of the biogas production from cattle waste, xylanolytic bacteria were isolated from enrichments of fermenting cattle manure. From 34 isolates, mostly Gram-negative rods, a typical strain was investigated in more detail. It was an anaerobic non-sporeforming, Gramnegative rod, which was motile with peritrichous flagella. This organism fermented xylan and many soluble sugars (glucose, cellobiose, mannose, xylose, arabinose). Other hemicelluloses such as gum xanthan, laminaran, locust bean gum, and gum arabic were not utilized. It also could not use cellulose. Fermentation products were carbon dioxide, hydrogen, acetate and ethanol. The bacterium produced carboxymethylcellulase and xylanase, especially when growing on xylan. Growth was optimal between 25°C and 40°C and between pH 6.5 and 7.5. The guanine plus cytosine content of the DNA was 34.8±0.8%. The isolate was identified as a member of the genus Bacteroides, and a new species is proposed: Bacteroides xylanolyticus (xylan dissolving). The type strain of B. xylanolyticus is strain X5-1 (DSM 3808). 相似文献