Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 31 for “"methanogenic archaea"”.
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Activity of methanogenic archaea under simulated Mars analog conditions
… on Mars. Therefore the phylogenetically old methanogenic archaea, which have evolved under early Earth conditions, are often used as model-organisms in astrobiological studies to investigate the potential of life to exist in possible extraterrestrial habitats on our neighboring planet. In …
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Sulfite reductase and thioredoxin in oxidative stress responses of methanogenic archaea
… These obligate anaerobes belonging to the archaeal domain inhabit diverse anoxic environments such as rice paddy fields, human guts, rumen of ruminants, and hydrothermal vents. In these habitats, methanogens are often exposed to O₂ and previous studies have shown that many methanogens are …
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Expanding the genetic toolbox for methanogenic archaea and investigating ferredoxin redox circuit formation in Methanosarcina acetivorans
Methane-producing archaea (methanogens) occupy a number of anoxic niches from soil sediments to the gastrointestinal tracts of numerous animals. In these anaerobic environments methanogens have specialized in converting simple substrates like carbon dioxide (CO2), formate, and acetate to methane …
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Characterization of Enzymes of the Methylcoenzyme M Reductase System From Methanobacterium Thermoautotrophicum and Identification of a Factor Required for Growth of Methanomicrobium Mobile
… (CH$\sb3$-S-coenzyme M, CH$\sb3$-S-CoM) by methanogenic archaea is catalyzed by a methylcoenzyme M reductase (MR). In Methanobacterium thermoautotrophicum strain $\Delta$H, this reaction has been shown to require minimally two additional protein components (A2 and A3a), as well as ATP and a …
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Methanogens from Siberian permafrost as models for life on Mars : response to simulated martian conditions and biosignature characterization
… permafrost in large numbers. Among these are methanogenic archaea, which are anaerobic chemotrophic microorganisms that meet many of the metabolic and physiological requirements for survival on the martian subsurface. Moreover, methanogens from Siberian permafrost are extremely resistant …
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Microbial communities and their response to Pleistocene and Holocene climate variabilities in the Russian Arctic
… associated with an expansion of bacterial and archaeal communities throughout the Russian Arctic, similar to present day conditions. Different from this situation, past glacial and stadial periods experienced a substantial decrease in the abundance of Bacteria and Archaea. This trend can also …
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Unexpected metabolic versatility discovered using new high-throughput genetic approaches in a model methanogen
… of Methanococcus maripaludis as a model for methanogenic archaea in general. In this introduction, I will discuss our current understanding of methanogenesis and the metabolic capabilities of hydrogenotrophic methanogens while also highlighting gaps in our understanding. In subsequent …
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Insights into substrate utilization and transcriptional regulation in methanosarcina
Methanogenic archaea are strictly anaerobic organisms responsible for the production of all biologically produced methane making them key players of the global carbon cycle. These unusual organisms derive their energy from the reduction of one-carbon (C-1) compounds to methane. Among methanogenic …
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Identifying ecological differentiation in microbial communities across taxonomic scales
… bacterial community to a single population of methanogenic archaea. At the broadest taxonomic scale, I used a whole-ecosystem disturbance along with 16S rRNA 454-pyrosequencing to identify ecologically relevant distinctions among taxonomic groups defined at various taxonomic scales. The …
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Comparative analysis of primate hydrogenotrophic microbiota
… functioning of this ecosystem. Methanogenesis by methanogenic Archaea and sulfate reduction by sulfate reducing bacteria (SRB) are the major hydrogenotrophic pathways in the human colon. Hydrogen metabolism by these microbes has an important impact on the colonic health. Methanogenic status of …
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Fabrication, solute transport characterization and biological application of a microfluidic gradient chamber
… can be controlled. A strictly anaerobic methanogenic archaea species (Methanosarcina acetivorans) was grown in the MGC by introducing high salt media along the two boundary channels. The M. acetivorans produced a large amount of methane gas, which ultimately displaced the liquid media in …
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Investigating the Distribution and Biosynthesis of Modified F<sub>430</sub> Cofactors in Methanogenic and Methanotrophic Archaea
… production of methane and is utilized by methanogenic archaea (methanogens) to generate energy. This process is responsible for 70% of total atmospheric methane, a potent greenhouse gas and an important energy source (natural gas). In the future, reversing methanogenesis in an engineered …
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Enzymology and Physiology of a New Type of Phosphoenolpyruvate Carboxylase and the Development of a Pyruvate Carboxylase Expression System
… is critical for cell carbon synthesis in the methanogenic archaea. Therefore OAA-generating enzymes are essential for the survival of methanogens. In part of this study we investigated archaeal-type phosphoenolpyruvate carboxylase (PpcA), a new type of phosphoenolpyruvate carboxylase, which is …
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Assessing the co-production of ammonia and methane for resource recovery optimization
… content, following the optimum pH range for methanogenic Archaea. The addition of phosphate buffer to maintain the pH values close to neutral was also studied. Results suggest that higher concentrations caused a more significant reduction on the biogas yield, and the phosphate buffer also …
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Recombinant Expression and Assembly of Methyl Coenzyme-M reductase
… enzyme involved in the production of methane by methanogenic archaea and its consumption by anaerobic methanotrophs (ANME). MCR is a multimeric complex composed of six different subunits arranged in a 2α, 2β, 2γ configuration that requires two molecules of its nickel-containing tetrapyrrole …
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Identification and Characterization of the Enzymes Involved in Biosynthesis of FAD and Tetrahydromethanopterin in Methanocaldococcus jannaschii
Methanogens belong to the archaeal domain, are anaerobes and produce methane from CO2 or other simple carbon compounds. Methanogenesis is a key process of the global carbon cycle and methanogens produce about 75-85% of all methane emissions. Besides the universally occurring coenzymes that are …
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Mechanistic investigations of class III anaerobic ribonucleotide reductases
… class III RNR, found in anaerobic bacteria and archaea, which uses an O₂-sensitive glycyl radical cofactor (G*). The class III RNRs studied to date couple nucleotide reduction to the oxidation of formate to CO₂. We started by studying the Escherichia coli class III RNR (NrdD1), and found that …
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The production of biogenic gases in the marine environment
… aerobic pelagic environment. The occurrence of methanogenic Archaea<br/>specifically associated with copepod faecal pellets from mono-species cultures of copepods, environmental samples and total pelagic particulates was investigated using 16S rRNA gene libraries. Clusters of sequences closely …
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Degradation of the Insensitive Munitions Compound 3-Nitro-1,2,4-triazol-5-one (NTO) via Sequential Reducing-Oxidizing Conditions
… organisms, including microorganisms (i.e., methanogenic archaea, aerobic heterotrophs, and Aliivibrio fischeri (Microtox assay)), the microcrustacean Daphnia magna, and zebrafish embryos (Danio rerio). The results indicate that the reductive biotransformation of NTO could enhance or lower …
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Computer-assisted generation and curation of genome-scale metabolic models with case studies in the methanogen genus Methanosarcina
Methanogenic archaea, organisms that make methane as a byproduct of their metabolism, play a critical role in the global carbon cycle and have potential as a source of renewable biofuels. As a result, there has been a great deal of interest in understanding how methanogenesis works. A wide array of …
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