Anaerobic Metabolism: Linkages to Trace Gases and Aerobic Processes

Megonigal, J. Patrick; Hines, Mark E.; Visscher, Pieter T.

doi:10.1016/b0-08-043751-6/08132-9

Cited by 273 publications

(247 citation statements)

References 1,207 publications

(801 reference statements)

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“…Organic matter mineralization, which influences the long-term burial of organic carbon and, thereby, regulates atmospheric oxygen concentrations (20), requires coupling between several functional groups of microorganisms (21). In this article, we report the unexpected discovery of temperaturedriven decoupling of key microbial groups involved in organic carbon mineralization.…”

Section: Discussionmentioning

confidence: 93%

Temperature-driven decoupling of key phases of organic matter degradation in marine sediments

Weston

Joye

2005

Proc. Natl. Acad. Sci. U.S.A.

109

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The long-term burial of organic carbon in sediments results in the net accumulation of oxygen in the atmosphere, thereby mediating the redox state of the Earth's biosphere and atmosphere. Sediment microbial activity plays a major role in determining whether particulate organic carbon is recycled or buried. A diverse consortium of microorganisms that hydrolyze, ferment, and terminally oxidize organic compounds mediates anaerobic organic matter mineralization in anoxic sediments. Variable temperature regulation of the sequential processes, leading from the breakdown of complex particulate organic carbon to the production and subsequent consumption of labile, low-molecular weight, dissolved intermediates, could play a key role in controlling rates of overall organic carbon mineralization. We examined sediment organic carbon cycling in a sediment slurry and in flow through bioreactor experiments. The data show a variable temperature response of the microbial functional groups mediating organic matter mineralization in anoxic marine sediments, resulting in the temperaturedriven decoupling of the production and consumption of organic intermediates. This temperature-driven decoupling leads to the accumulation of labile, low-molecular weight, dissolved organic carbon at low temperatures and low-molecular weight dissolved organic carbon limitation of terminal metabolism at higher temperatures.carbon cycle ͉ fermentation ͉ terminal metabolism ͉ sulfate reduction M icrobes performing the terminal mineralization of organic carbon to metabolic end products ( Fig. 1) are limited largely to labile, low-molecular weight (LMW), dissolved organic matter [LMW-dissolved organic carbon (DOC)] (molecular mass, Ͻ600 Da) that can be transported across cellular membranes (1). Particulate organic matter is initially broken down into high-molecular weight dissolved organic matter through extracellular enzymatic hydrolysis. High-molecular weight dissolved organic matter is further hydrolyzed and fermented to LMW-DOC, such as volatile fatty acids (VFAs) (2-4), that are available for terminal metabolism ( Fig. 1) (2,5,6). Despite the importance of hydrolysis͞fermentation in organic matter mineralization, relatively little is known about the environmental controls on this process.We examined the regulation of organic carbon mineralization in anoxic coastal marine sediments. A large fraction (55%) of global sediment organic matter oxidation occurs in coastal marine sediments, even though they account for only 7.5% of the total area of marine sediments (7,8). High metabolic rates in these sediments deplete oxygen within millimeters of the sediment-water interface, and the majority of organic matter mineralization proceeds via anaerobic pathways (9), mainly sulfate reduction (9-12). The organic carbon consumed by sulfatereducing bacteria is often VFAs, such as acetic acid (5, 6).Temperature and substrate availability influence the rates and seasonal patterns of microbial activity (13) and, hence, organic matter mineralization (14). For instance,...

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Section: Discussionmentioning

confidence: 93%

Temperature-driven decoupling of key phases of organic matter degradation in marine sediments

Weston

Joye

2005

Proc. Natl. Acad. Sci. U.S.A.

109

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“…Thus, we do not consider Fe(II) oxidation at very low pH further here. Several recent reviews provide detailed information on various aspects of circumneutral FeOB (Emerson, 2000;Croal et al, 2004a;Edwards et al, 2004;Emerson and Weiss, 2004;Megonigal et al, 2004).…”

Section: Iron Oxidationmentioning

confidence: 99%

“…In contrast, other FeRB, including Shewanella putrefaciens and S. alga, can use H 2 or complex organic molecules (e.g., lactate, formate) as electron donors but are generally only capable of incomplete oxidation of these compounds to acetate (Lovley, 2000). For more information on the physiology of FeRB and their environmental importance, the reader is referred to recent reviews by Lovley (2000), Thamdrup (2000), Straub et al (2001), Croal et al (2004a), andMegonigal et al (2004).…”

Section: Iron Reductionmentioning

confidence: 99%

Microbial Oxidation and Reduction of Iron in the Root Zone and Influences on Metal Mobility

Neubauer

Emerson

Megonigal

2007

Biophysico‐Chemical Processes of Heavy Metals and Metalloids in Soil Environments

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“…In anaerobic soils, fermenting microbes and H 2 -producing acetogens transform organic molecules, ultimately producing acetate, H 2 , and CO 2 . In freshwater anaerobic systems, acetate and H 2 are the primary substrates utilized by two classes of methanogens (acetotrophic and hydrogenotrophic), producing CH 4 as a byproduct (Megonigal et al, 2004;Segers, 1998). The presence of alternative electron acceptors (e.g., NO − 3 , Fe 3+ , Mn 4+ , SO 2− 4 ) suppresses CH 4 production via: (1) reduction of C substrate levels; (2) increase in redox potential; and (3) toxicity to methanogens (Segers and Kengen, 1998).…”

Section: Clm4 Ch 4 Biogeochemistry Model (Clm4me) Descriptionmentioning

confidence: 99%

Barriers to predicting changes in global terrestrial methane fluxes: analyses using CLM4Me, a methane biogeochemistry model integrated in CESM

et al. 2011

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Abstract. Terrestrial net CH 4 surface fluxes often represent the difference between much larger gross production and consumption fluxes and depend on multiple physical, biological, and chemical mechanisms that are poorly understood and represented in regional-and global-scale biogeochemical models. To characterize uncertainties, study feedbacks between CH 4 fluxes and climate, and to guide future model development and experimentation, we developed and tested a new CH 4 biogeochemistry model (CLM4Me) integrated in the land component (Community Land Model; CLM4) of the Community Earth System Model (CESM1). CLM4Me includes representations of CH 4 production, oxidation, aerenchyma transport, ebullition, aqueous and gaseous diffusion, and fractional inundation. As with most global models, CLM4 lacks important features for predicting current and future CH 4 fluxes, including: vertical representation of soil organic matter, accurate subgrid scale hydrology, realistic representation of inundated system vegetation, anaerobic decomposition, thermokarst dynamics, and aqueous chemistry. We compared the seasonality and magnitude of predicted CH 4 emissions to observations from 18 sites and three global atmospheric inversions. Simulated net CH 4 emissions using our baseline parameter set were 270, 160, 50, and 70 Tg CH 4 yr −1 globally, in the tropics, in the temperate zone, and north of 45 • N, respectively; these values are within the range of previous estimates. We then used the model to characterize the sensitivity of regional and global CH 4 emission estimates to uncertainties in model paCorrespondence to: W. J. Riley (wjriley@lbl.gov) rameterizations. Of the parameters we tested, the temperature sensitivity of CH 4 production, oxidation parameters, and aerenchyma properties had the largest impacts on net CH 4 emissions, up to a factor of 4 and 10 at the regional and gridcell scales, respectively. In spite of these uncertainties, we were able to demonstrate that emissions from dissolved CH 4 in the transpiration stream are small (<1 Tg CH 4 yr −1 ) and that uncertainty in CH 4 emissions from anoxic microsite production is significant. In a 21st century scenario, we found that predicted declines in high-latitude inundation may limit increases in high-latitude CH 4 emissions. Due to the high level of remaining uncertainty, we outline observations and experiments that would facilitate improvement of regional and global CH 4 biogeochemical models.

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Anaerobic Metabolism: Linkages to Trace Gases and Aerobic Processes

Cited by 273 publications

References 1,207 publications

Temperature-driven decoupling of key phases of organic matter degradation in marine sediments

Temperature-driven decoupling of key phases of organic matter degradation in marine sediments

Microbial Oxidation and Reduction of Iron in the Root Zone and Influences on Metal Mobility

Barriers to predicting changes in global terrestrial methane fluxes: analyses using CLM4Me, a methane biogeochemistry model integrated in CESM

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