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Methanosarcina barkeri
About: Methanosarcina barkeri is a research topic. Over the lifetime, 703 publications have been published within this topic receiving 32151 citations.
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TL;DR: This study fingerprint and identify the methanogens present in three different types of UASB granules that had been used to treat winery, brewery and peach-lye canning effluents using polymerase chain reaction (PCR)-based denaturing gradient gel electrophoresis (DGGE) and DNA sequence analysis.
75 citations
TL;DR: These experiments revealed the first genes involved in the biosynthesis of compatible solutes in methanogens, including lysine-2,3-aminomutase and β-lysine acetyltransferase, which were identified on the chromosomes of the methanogenic archaea Methanosarcina mazei Gö1.
Abstract: The compatible solute N(epsilon)-acetyl-beta-lysine is unique to methanogenic archaea and is produced under salt stress only However, the molecular basis for the salt-dependent regulation of N(epsilon)-acetyl-beta-lysine formation is unknown Genes potentially encoding lysine-2,3-aminomutase (ablA) and beta-lysine acetyltransferase (ablB), which are assumed to catalyze N(epsilon)-acetyl-beta-lysine formation from alpha-lysine, were identified on the chromosomes of the methanogenic archaea Methanosarcina mazei Go1, Methanosarcina acetivorans, Methanosarcina barkeri, Methanococcus jannaschii, and Methanococcus maripaludis The order of the two genes was identical in the five organisms, and the deduced proteins were very similar, indicating a high degree of conservation of structure and function Northern blot analysis revealed that the two genes are organized in an operon (termed the abl operon) in M mazei Go1 Expression of the abl operon was strictly salt dependent The abl operon was deleted in the genetically tractable M maripaludis Delta(abl) mutants of M maripaludis no longer produced N(epsilon)-acetyl-beta-lysine and were incapable of growth at high salt concentrations, indicating that the abl operon is essential for N(epsilon)-acetyl-beta-lysine synthesis These experiments revealed the first genes involved in the biosynthesis of compatible solutes in methanogens
74 citations
TL;DR: The mechanism of ammonia assimilation in Methanosarcina barkeri and Methanobacterium thermoautotrophicum was documented by analysis of enzyme activities, 13NH3 incorporation studies, and comparison of growth and enzyme activity levels in continuous culture.
Abstract: The mechanism of ammonia assimilation in Methanosarcina barkeri and Methanobacterium thermoautotrophicum was documented by analysis of enzyme activities, 13NH3 incorporation studies, and comparison of growth and enzyme activity levels in continuous culture. Glutamate accounted for 65 and 52% of the total amino acids in the soluble pools of M. barkeri and M. thermoautotrophicum. Both organisms contained significant activities of glutamine synthetase, glutamate synthase, glutamate oxaloacetate transaminase, and glutamate pyruvate transaminase. Hydrogen-reduced deazaflavin-factor 420 or flavin mononucleotide but not NAD, NADP, or ferredoxin was used as the electron donor for glutamate synthase in M. barkeri. Glutamate dehydrogenase activity was not detected in either organism, but alanine dehydrogenase activity was present in M. thermoautotrophicum. The in vivo activity of the glutamine synthetase was verified in M. thermoautotrophicum by analysis of 13NH3 incorporation into glutamine, glutamate, and alanine. Alanine dehydrogenase and glutamine synthetase activity varied in response to [NH4+] when M. thermoautotrophicum was cultured in a chemostat with cysteine as the sulfur source. Alanine dehydrogenase activity and growth yield (grams of cells/mole of methane) were highest when the organism was cultured with excess ammonia, whereas growth yield was lower and glutamine synthetase was maximal when ammonia was limiting.
74 citations
TL;DR: Results indicate that MbHdrD harbors the active site of heterodisulfide reduction and that a flavin is not involved in catalysis.
Abstract: Heterodisulfide reductase from methanol-grown cells of Methanosarcina barkeri (MbHdrDE) is a membrane-bound enzyme composed of a 46-kDa subunit MbHdrD and a 23-kDa subunit MbHdrE. The enzyme has been shown to contain 0.6 mol heme and 20 mol Fe/S per mol heterodimer. In addition, substoichiometric amounts of FAD, thought to be an essential component of the active enzyme, were detected. We have now obtained preparations of active heterodisulfide reductase in high yields completely devoid of a flavin. Cloning and sequencing of the genes encoding MbHdrD and MbHdrE, which were found to form a transcription unit hdrED, revealed that both subunits also lack an FAD-binding motif. MbHdr thus differs from heterodisulifde reductase from Methanobacterium thermoautotrophicum (MtHdr), which is a flavo iron-sulfur protein composed of the subunits MtHdrA (80 kDa), MtHdrB (36 kDa) and MtHdrC (21 kDa), the subunit HdrA harboring the flavin-binding site. Sequence comparisons revealed that the N-terminal third of MbHdrD, which contained two sequence motifs for [4Fe-4S] clusters, is similar to MtHdrC and that the C-terminal two thirds of MbHdrD are similar to MtHdrB. Thus, MbHdrD and MtHdrC are structurally equivalent subunits. MbHdrE shows sequence similarity to b-type cytochromes, in agreement with the finding that this subunit contains a heme. These and other results indicate that MbHdrD harbors the active site of heterodisulfide reduction and that a flavin is not involved in catalysis. Since MbHdrD contains only iron-sulfur clusters, a mechanism of disulfide reduction involving one electron rather than two electron-transfer reactions has to be considered such as operative in ferredoxin :thioredoxin reductases from chloroplasts and cyanobacteria.
74 citations
TL;DR: It was shown that C. sporogenes was unable to catabolize betaine as a single substrate, and betaine, however, was reduced to trimethylamine and acetate under an atmosphere of molecular hydrogen.
Abstract: Growing and nongrowing cells of Clostridium sporogenes fermented betaine with l-alanine, l-valine, l-leucine, and l-isoleucine as electron donors in a coupled oxidation-reduction reaction (Stickland reaction). For the substrate combinations betaine and l-alanine and betaine and l-valine balance studies were performed; the results were in agreement with the following fermentation equation: 1 R- CH(NH2)-COOH + 2 betaine + 2 H2O → 1 R-COOH + 1 CO2 + 1 NH3 + 2 trimethylamine + 2 acetate. Growth and production of trimethylamine were strictly dependent on the presence of selenite in the medium. With cell suspensions it was shown that C. sporogenes was unable to catabolize betaine as a single substrate. Betaine, however, was reduced to trimethylamine and acetate under an atmosphere of molecular hydrogen. For the reduction of betaine by cell extracts of C. sporogenes, dimercaptans such as 1,4-dithiothreitol could serve as electron donors. No betaine reductase activity was detected in cells grown in a complex medium without betaine. The pH optimum of betaine reductase was at pH 7.3. When C. sporogenes was cocultured with Methanosarcina barkeri strain Fusaro on betaine together with l-alanine, an almost complete conversion of the two substrates to CH4, NH3, and presumably CO2 was observed.
73 citations