scholarly journals Mechanisms for Electron Uptake by Methanosarcina acetivorans during Direct Interspecies Electron Transfer

mBio ◽  
2021 ◽  
Author(s):  
Dawn E. Holmes ◽  
Jinjie Zhou ◽  
Toshiyuki Ueki ◽  
Trevor Woodard ◽  
Derek R. Lovley
Keyword(s):  
Carbon Dioxide ◽  
Organic Matter ◽  
Global Carbon Cycle ◽  
Effective Strategy ◽  
Methanosarcina Acetivorans ◽  
Direct Interspecies Electron Transfer ◽  
Interspecies Electron Transfer ◽  
Anaerobic Soils ◽  
Soils And Sediments ◽  
Global Carbon

The conversion of organic matter to methane plays an important role in the global carbon cycle and is an effective strategy for converting wastes to a useful biofuel. The reduction of carbon dioxide to methane accounts for approximately a third of the methane produced in anaerobic soils and sediments as well as waste digesters.

scholarly journals Mechanisms for Electron Uptake by Methanosarcina acetivorans During Direct Interspecies Electron Transfer

2021 ◽  
Author(s):  
Dawn Holmes ◽  
Jinjie Zhou ◽  
Toshiyuki Ueki ◽  
Trevor Woodard ◽  
Derek Lovley
Keyword(s):  
Carbon Dioxide ◽  
Electron Transfer ◽  
Outer Surface ◽  
Expression Patterns ◽  
Amino Acid Content ◽  
Carbon Dioxide Reduction ◽  
Methanosarcina Acetivorans ◽  
Electrically Conductive ◽  
Direct Interspecies Electron Transfer ◽  
Interspecies Electron Transfer

Direct interspecies electron transfer (DIET) between bacteria and methanogenic archaea appears to be an important syntrophy in both natural and engineered methanogenic environments. However, the electrical connections on the outer surface of methanogens and the subsequent processing of electrons for carbon dioxide reduction to methane are poorly understood. Here we report that the genetically tractable methanogen Methanosarcina acetivorans can grow via DIET in co-culture with Geobacter metallireducens serving as the electron-donating partner. Comparison of gene expression patterns in M. acetivorans grown in co-culture versus pure culture growth on acetate revealed that transcripts for the outer-surface, multi-heme, c-type cytochrome MmcA were higher during DIET-based growth. Deletion of mmcA inhibited DIET. The high aromatic amino acid content of M. acetivorans archaellins suggests that they might assemble into electrically conductive archaella. A mutant that could not express archaella was deficient in DIET. However, this mutant grew in DIET-based co-culture as well as the archaella-expressing parental strain in the presence of granular activated carbon, which was previously shown to serve as a substitute for electrically conductive pili as a conduit for long-range interspecies electron transfer in other DIET-based co-cultures. Transcriptomic data suggesting that the membrane-bound Rnf, Fpo, and HdrED complexes also play a role in DIET were incorporated into a charge-balanced model illustrating how electrons entering the cell through MmcA can yield energy to support growth from carbon dioxide reduction. The results are the first genetics-based functional demonstration of likely outer-surface electrical contacts for DIET in a methanogen.

scholarly journals Potential for Direct Interspecies Electron Transfer in Methanogenic Wastewater Digester Aggregates

mBio ◽  
2011 ◽  
Vol 2 (4) ◽  
Author(s):  
Masahiko Morita ◽  
Nikhil S. Malvankar ◽  
Ashley E. Franks ◽  
Zarath M. Summers ◽  
Ludovic Giloteaux ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Organic Matter ◽  
Geobacter Sulfurreducens ◽  
Anaerobic Sludge ◽  
Rrna Gene ◽  
Electrically Conductive ◽  
Content Type ◽  
Direct Interspecies Electron Transfer ◽  
Interspecies Electron Transfer ◽  
Anaerobic Soils

ABSTRACTMechanisms for electron transfer within microbial aggregates derived from an upflow anaerobic sludge blanket reactor converting brewery waste to methane were investigated in order to better understand the function of methanogenic consortia. The aggregates were electrically conductive, with conductivities 3-fold higher than the conductivities previously reported for dual-species aggregates ofGeobacterspecies in which the two species appeared to exchange electrons via interspecies electron transfer. The temperature dependence response of the aggregate conductance was characteristic of the organic metallic-like conductance previously described for the conductive pili ofGeobacter sulfurreducensand was inconsistent with electron conduction through minerals. Studies in which aggregates were incubated with high concentrations of potential electron donors demonstrated that the aggregates had no significant capacity for conversion of hydrogen to methane. The aggregates converted formate to methane but at rates too low to account for the rates at which that the aggregates syntrophically metabolized ethanol, an important component of the reactor influent.Geobacterspecies comprised 25% of 16S rRNA gene sequences recovered from the aggregates, suggesting thatGeobacterspecies may have contributed to some but probably not all of the aggregate conductivity. Microorganisms most closely related to the acetate-utilizingMethanosaeta conciliiaccounted for more than 90% of the sequences that could be assigned to methane producers, consistent with the poor capacity for hydrogen and formate utilization. These results demonstrate for the first time that methanogenic wastewater aggregates can be electrically conductive and suggest that direct interspecies electron transfer could be an important mechanism for electron exchange in some methanogenic systems.IMPORTANCEThe conversion of waste organic matter to methane is an important bioenergy strategy, and a similar microbial metabolism of complex organic matter in anaerobic soils and sediments plays an important role in the global carbon cycle. Studies with laboratory cultures have demonstrated that hydrogen or formate can serve as an electron shuttle between the microorganisms degrading organic compounds and methanogens. However, the importance of hydrogen and formate as intermediates in the conversion of organic matter to methane in natural communities is less clear. The possibility that microorganisms within some natural methanogenic aggregates may directly exchange electrons, rather than producing hydrogen or formate as an intermediary electron carrier, is a significant paradigm shift with implications for the modeling and design of anaerobic wastewater reactors and for understanding how methanogenic communities will respond to environmental perturbations.

scholarly journals Organic Geochemical Characteristics of the Upper Cretaceous Qingshankou Formation Oil Shales in the Fuyu Oilfield, Songliao Basin, China: Implications for Oil-Generation Potential and Depositional Environment

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4778 ◽  
Author(s):  
Wentong He ◽  
Youhong Sun ◽  
Wei Guo ◽  
Xuanlong Shan ◽  
Siyuan Su ◽  
...  
Keyword(s):  
Organic Matter ◽  
Carbon Cycle ◽  
Depositional Environment ◽  
Global Carbon Cycle ◽  
Songliao Basin ◽  
Oil Generation ◽  
Oil Shales ◽  
Extractable Organic Matter ◽  
The Impact ◽  
Global Carbon

The Cretaceous Era has always been a focus of geologic and palaeoenvironmental studies. Previous researchers believed that the impact of the global carbon cycle represents significant short-term global biogeochemical fluctuations, leading to the formation of a large number of organic rich sediments in the marine environment. During the Turonian, a large number of organic-rich oil shales were deposited in the lakes of the Songliao Basin in the Qingshankou Formation. How the depositional environment affected the formation of oil shales in continental lakes and the characteristics of these oil shales remain controversial. In this paper, through sampling of Qingshankou Formation strata, various testing methods are used to provide a variety of new data to study the characteristics of oil shales and palaeoenvironment evolution history in the Songliao Basin. The research of the sediments in the Qingshankou Formation in the Fuyu oilfield, Songliao Basin, via result analysis revealed that the oil shales possess an excellent oil-generation potential with moderate-high total organic carbon (TOC) levels (0.58–9.43%), high hydrogen index (HI) values (265–959 mg hydrocarbons (HC)/g TOC), high extractable organic matter (EOM) levels (2.50–6.96 mg/g TOC) and high hydrocarbon fractions (48–89%). The sources of the organic matter were mainly zooplankton, red algae and higher plants (including marine organisms). The aqueous palaeoenvironment of the Qingshankou Formation was a saline water environment with a high sulfate concentration, which promoted an increase in nutrients and stratification of the water density in the lake basin. Oxygen consumption in the bottom water layer promoted the accumulation and burial of high-abundance organic matter, thus forming the high-quality oil shales in the Qingshankou Formation. The global carbon cycle, warm-humid palaeoclimate, dynamic local biogeochemical cycling and relative passive tectonism were the most likely reasons for the TOC increase and negative δ13Corg deviation.

A 35-million-year record of seawater stable Sr isotopes reveals a fluctuating global carbon cycle

Science ◽  
2021 ◽  
Vol 371 (6536) ◽  
pp. 1346-1350
Author(s):  
Adina Paytan ◽  
Elizabeth M. Griffith ◽  
Anton Eisenhauer ◽  
Mathis P. Hain ◽  
Klaus Wallmann ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Atmospheric Carbon Dioxide ◽  
Global Carbon Cycle ◽  
Sr Isotopes ◽  
Sr Isotope ◽  
Sources And Sinks ◽  
Isotope Record ◽  
Biogenic Carbonates ◽  
Stable Strontium ◽  
Global Carbon

Changes in the concentration and isotopic composition of the major constituents in seawater reflect changes in their sources and sinks. Because many of the processes controlling these sources and sinks are tied to the cycling of carbon, such records can provide insights into what drives past changes in atmospheric carbon dioxide and climate. Here, we present a stable strontium (Sr) isotope record derived from pelagic marine barite. Our δ88/86Sr record exhibits a complex pattern, first declining between 35 and 15 million years ago (Ma), then increasing from 15 to 5 Ma, before declining again from ~5 Ma to the present. Numerical modeling reveals that the associated fluctuations in seawater Sr concentrations are about ±25% relative to present-day seawater. We interpret the δ88/86Sr data as reflecting changes in the mineralogy and burial location of biogenic carbonates.

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