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61.
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
62.
Seasonal investigations of methane distribution and rates of its oxidation and generation in the water column and sediments of the Black Sea northwestern shelf were carried out within the framework of the interdisciplinary projects European River–Ocean Systems (EROS-2000, EROS-21) and Biogenic Gases Exchange in the Black Sea (BigBlack) in August 1995, May 1997, and December 1999. Experiments that involved the addition of 14CH3COONa and 14CO2 to sediment samples showed the main part of methane to be formed from CO2. Maximum values of methane production (up to 559 mol/(m2 day)) were found in coastal sediments in summer time. In winter and spring, methane production in the same sediments did not exceed 3.6–4.2 mol/(m2 day). The 13C values of methane ranged from –70.7 to –81.8, demonstrating its microbial origin and contradicting the concept of the migration of methane from cold seeps or from the oil fields located on the Black Sea shelf. Experiments that involved the addition of 14CH4 to water and sediment samples showed that a considerable part of methane is oxidized in the upper horizons of bottom sediments and in the water column. Nevertheless, it was found that, in summer, part of the methane (from 6.8 to 320 mol/(m2 day)) arrives in the atmosphere. 相似文献
63.
Hiroyuki Imachi Ken Aoi Eiji Tasumi Yumi Saito Yuko Yamanaka Yayoi Saito Takashi Yamaguchi Hitoshi Tomaru Rika Takeuchi Yuki Morono Fumio Inagaki Ken Takai 《The ISME journal》2011,5(12):1913-1925
Microbial methanogenesis in subseafloor sediments is a key process in the carbon cycle on the Earth. However, the cultivation-dependent evidences have been poorly demonstrated. Here we report the cultivation of a methanogenic microbial consortium from subseafloor sediments using a continuous-flow-type bioreactor with polyurethane sponges as microbial habitats, called down-flow hanging sponge (DHS) reactor. We anaerobically incubated methane-rich core sediments collected from off Shimokita Peninsula, Japan, for 826 days in the reactor at 10 °C. Synthetic seawater supplemented with glucose, yeast extract, acetate and propionate as potential energy sources was provided into the reactor. After 289 days of operation, microbiological methane production became evident. Fluorescence in situ hybridization analysis revealed the presence of metabolically active microbial cells with various morphologies in the reactor. DNA- and RNA-based phylogenetic analyses targeting 16S rRNA indicated the successful growth of phylogenetically diverse microbial components during cultivation in the reactor. Most of the phylotypes in the reactor, once it made methane, were more closely related to culture sequences than to the subsurface environmental sequence. Potentially methanogenic phylotypes related to the genera Methanobacterium, Methanococcoides and Methanosarcina were predominantly detected concomitantly with methane production, while uncultured archaeal phylotypes were also detected. Using the methanogenic community enrichment as subsequent inocula, traditional batch-type cultivations led to the successful isolation of several anaerobic microbes including those methanogens. Our results substantiate that the DHS bioreactor is a useful system for the enrichment of numerous fastidious microbes from subseafloor sediments and will enable the physiological and ecological characterization of pure cultures of previously uncultivated subseafloor microbial life. 相似文献
64.
Scott Godwin Alicia Kang Lisa-Maree Gulino Mike Manefield Maria-Luisa Gutierrez-Zamora Marco Kienzle Diane Ouwerkerk Kerri Dawson Athol V Klieve 《The ISME journal》2014,8(9):1855-1865
Kangaroos ferment forage material in an enlarged forestomach analogous to the rumen, but in contrast to ruminants, they produce little or no methane. The objective of this study was to identify the dominant organisms and pathways involved in hydrogenotrophy in the kangaroo forestomach, with the broader aim of understanding how these processes are able to predominate over methanogenesis. Stable isotope analysis of fermentation end products and RNA stable isotope probing (RNA-SIP) were used to investigate the organisms and biochemical pathways involved in the metabolism of hydrogen and carbon dioxide in the kangaroo forestomach. Our results clearly demonstrate that the activity of bacterial reductive acetogens is a key factor in the reduced methane output of kangaroos. In in vitro fermentations, the microbial community of the kangaroo foregut produced very little methane, but produced a significantly greater proportion of acetate derived from carbon dioxide than the microbial community of the bovine rumen. A bacterial operational taxonomic unit closely related to the known reductive acetogen Blautia coccoides was found to be associated with carbon dioxide and hydrogen metabolism in the kangaroo foregut. Other bacterial taxa including members of the genera Prevotella, Oscillibacter and Streptococcus that have not previously been reported as containing hydrogenotrophic organisms were also significantly associated with metabolism of hydrogen and carbon dioxide in the kangaroo forestomach. 相似文献
65.
66.
Bert Engelen Katja Ziegelmüller Lars Wolf Beate Köpke Antje Gittel Heribert Cypionka 《Geomicrobiology journal》2013,30(1):56-66
The importance of crustal fluid chemical composition in driving the marine deep subseafloor biosphere was examined in northeast Pacific ridge-flank sediments. At IODP Site U1301, sulfate from crustal fluids diffuses into overlying sediments, forming a transition zone where sulfate meets in situ-produced methane. Enhanced cell counts and metabolic activity suggest that sulfate stimulates microbial respiration, specifically anaerobic methane oxidation coupled to sulfate reduction. Cell counts and activity are also elevated in basement-near layers. Owing to the worldwide expansion of the crustal aquifer, we postulate that crustal fluids may fuel the marine deep subseafloor biosphere on a global scale. 相似文献
67.
Mark D. Dettling Joseph B. Yavitt Hinsby Cadillo-Quiroz Christine Sun Stephen H. Zinder 《Geomicrobiology journal》2013,30(3-4):247-259
Rates of methanogenesis vary widely in peat soils, yet the reasons are poorly known. We examined rates of methanogenesis and methanogen diversity in relation to soil chemical and biological characteristics in 2 peatlands in New York State. One was an acidic (pH < 4.5) bog dominated by Sphagnum mosses and ericaceous shrubs, although deeper peat was derived from sedges. The other was a fen dominated by Carex lacustris sedges with near-neutral pH soil. At both sites, the most active rates of methanogenesis occurred in the top 20 cm of the peat profile, even when using a substrate-induced methanogenesis technique with added glucose that stimulated rates up to 2 μ mol g ? 1 day ?1 in the bog and 6 μ mol g ?1 day ?1 in the fen. Rates of anaerobic CO 2 production were greater in the bog (0–36 μ mol g ?1 day ?1 ) than in the fen (0–5 μ mol g ?1 day ?1 ), and added glucose induced greater rates in the sedge-derived peat from the bog than the fen. The peat soil was much more decomposed throughout the profile in the fen. Analysis of chemical elements in the peat profile revealed a striking anomaly: a very high concentration of Pb in surface peat of the bog, which might have constrained methanogenesis. Application of T-RFLP analysis to methanogens revealed dominance by a Methanomicrobiales E2 clade of H 2 /CO 2 users in the acidic peat soil of the bog, whereas deeper peat had a different Methanomicrobiales E1 clade, uncultured euryarchaeal rice cluster (RC)-I and RC-II groups, marine benthic group D (MBD) and a new cluster called subaqueous cluster (SC). In contrast, T-RFLP analysis of peat from the fen revealed co-dominance by Methanosaetaceae and Methanomicrobiales E1. The results showed complex relationships between rates of methanogenesis, methanogen populations and metabolic substrate availability with idiosyncratic interactions of trace chemical elements. 相似文献
68.
Microorganisms in a Disposal Site for Liquid Radioactive Wastes and Their Influence on Radionuclides
Tamara N. Nazina Evgenya A. Luk'yanova Elena V. Zakharova Larisa I. Konstantinova Stepan N. Kalmykov Andrei B. Poltaraus 《Geomicrobiology journal》2013,30(5):473-486
Deep subsurface horizons used for the disposal of liquid low- and intermediate-level radioactive wastes of the Siberian Chemical Complex (SCC, Russia) were studied by microbiological, radioisotope, and molecular biological methods. It was shown that a diverse microbial community inhabited the groundwater. The cell numbers of microorganisms of the major metabolic groups and the rates of sulfate reduction, denitrification, and methanogenesis in natural groundwater were low and increased in the zone of wastes dispersion. More than 40 strains belonging to the genera Kocuria, Microbacterium, Pseudomonas, Pantoea, Acinetobacter, Enterobacter, Klebsiella, Stenotrophomonas, Sphingomonas, Staphylococcus, Acidivorax, Shewanella, and Desulfosporosinus were isolated from the disposal sites. Among the isolates, the microorganisms were found that were able to concentrate actinides and other transuranium elements. Aerobic bacteria were able to sorb various radionuclides in laboratory experiments; however, biosorption was low in sample of groundwater and in carbonate solutions containing several radionuclides. Reduction of U(VI) by a sulfate-reducing enrichment culture from the site and reduction of U(VI) and Np(V) by an isolate Shewanella were observed in the presence of various organic substrates. These results show the necessity of further ecosystem characterization based on microbiological and radiochemical studies and modeling of biogeochemical processes at the deep disposal sites for liquid radioactive wastes. 相似文献
69.
T. C. Onstott L.-H. Lin M. Davidson B. Mislowack M. Borcsik J. Hall 《Geomicrobiology journal》2013,30(6):369-414
Water residing within crustal fractures encountered during mining at depths greater than 500 meters in the Witwatersrand basin of South Africa represents a mixture of paleo-meteoric water and 2.0–2.3 Ga hydrothermal fluid. The hydrothermal fluid is highly saline, contains abiogenic CH 4 and hydrocarbon, occasionally N 2 , originally formed at ~ 250–300°C and during cooling isotopically exchanged O and H with minerals and accrued H 2 , 4 He and other radiogenic gases. The paleo-meteoric water ranges in age from ~ 10 Ka to > 1.5 Ma, is of low salinity, falls along the global meteoric water line (GMWL) and is CO 2 and atmospheric noble gas-rich. The hydrothermal fluid, which should be completely sterile, has probably been mixing with paleo-meteoric water for at least the past ~100 Myr, a process which inoculates previously sterile environments at depths > 2.0 to 2.5 km. Free energy flux calculations suggest that sulfate reduction is the dominant electron acceptor microbial process for the high salinity fracture water and that it is 10 7 times that normally required for cell maintenance in lab cultures. Flux calculations also indicate that the potential bioavailable chemical energy increases with salinity, but because the fluence of bioavailable C, N and P also increase with salinity, the environment remains energy-limited. The 4 He concentrations and theoretical calculations indicate that the H 2 that is sustaining the subsurface microbial communities (e.g. H 2 -utilizing SRB and methanogens) is produced by water radiolysis at a rate of ~1 nM yr ?1 . Microbial CH 4 mixes with abiogenic CH 4 to produce the observed isotopic signatures and indicates that the rate of methanogenesis diminishes with depth from ~ 100 at < 1 kmbls, to < 0.01 nM yr ?1 at > 3 kmbls. Microbial Fe(III) reduction is limited due to the elevated pH. The δ13C of dissolved inorganic carbon is consistent with heterotrophy rather than autotrophy dominating the deeper, more saline environments. One potential source of the organic carbon may be microfilms present on the mineral surfaces. 相似文献
70.
T. N. Nazina A. A. Griror’yan Qingxian Feng N. M. Shestakova T. L. Babich N. K. Pavlova V. S. Ivoilov Fangtian Ni Jianqiang Wang Yuehui She Tingsheng Xiang Bowen Mei Zhibin Luo S. S. Belyaev M. V. Ivanov 《Microbiology》2007,76(3):297-309
Microbiological technology for the enhancement of oil recovery based on the activation of the stratal microflora was tested in the high-temperature horizons of the Kongdian bed (60°C) of the Dagang oil-field (China). This biotechnology consists in the pumping of a water-air mixture and nitrogen and phosphorus mineral salts into the oil stratum through injection wells in order to stimulate the activity of the stratal microflora which produce oil-releasing metabolites. Monitoring of the physicochemical, microbiological, and production characteristics of the trial site has revealed large changes in the ecosystem as a result of the application of biotechnology. The cell numbers of thermophilic hydrocarbon-oxidizing, fermentative, sulfate-reducing, and methanogenic microorganisms increased 10–10000-fold. The rates of methanogenesis and sulfate reduction increased in the near-bottom zone of the injection wells and of some production wells. The microbial oil transformation was accompanied by the accumulation of bicarbonate ions, volatile fatty acids, and biosurfactants in the formation waters, as well as of CH4 and CO2 both in the gas phase and in the oil. Microbial metabolites promoted the additional recovery of oil. As a result of the application of biotechnology, the water content in the production liquid from the trial site decreased, and the oil content increased. This allowed the recovery of more than 14000 tons of additional oil over 3.5 years. 相似文献