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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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Journal ArticleDOI
TL;DR: It is reported here that cells of M. barkeri grown on trimethylamine, H2/CO2, or acetate contain mainly isoenzyme II, which is found to have in common that they can catalyze the formation of methane from trimethyamine and H2, whereas only acetate-grown cells can mediate the formationof methane from acetate.
Abstract: Methanosarcina barkeri was recently shown to contain two cytoplasmic isoenzymes of methylcobalamin: coenzyme M methyltransferase (methyltransferase 2). Isoenzyme I predominated in methanol-grown cells and isoenzyme II in acetate-grown cells. It was therefore suggested that isoenzyme I functions in methanogenesis from methanol and isoenzyme II in methanogenesis from acetate. We report here that cells of M. barkeri grown on trimethylamine, H2/CO2, or acetate contain mainly isoenzyme II. These cells were found to have in common that they can catalyze the formation of methane from trimethylamine and H2, whereas only acetate-grown cells can mediate the formation of methane from acetate. Methanol-grown cells, which contained only low concentrations of isoenzyme II, were unable to mediate the formation of methane from both trimethylamine and acetate. These and other results suggest that isoenzyme II (i) is employed for methane formation from trimethylamine rather than from acetate, (ii) is constitutively expressed rather than trimethylamine-induced, and (iii) is repressed by methanol. The constitutive expression of isoenzyme II in acetate-grown M. barkeri can explain its presence in these cells. The N-terminal amino acid sequences of isoenzyme I and isoenzyme II were analyzed and found to be only 55% similar.

34 citations

Journal ArticleDOI
TL;DR: The reducing system of hydrogenase and ferredoxin was able to reduce dithiols, like dithiodiethanesulfonate and cystine to their monomers, in the presence of a corrinoid, which acts as an electron carrier.

34 citations

Journal ArticleDOI
TL;DR: The 5,10-methenyltetrahydromethanopterin cyclohydrolase from Methanosarcina barkeri was purified 313-fold to a specific activity of 470 mumol min-1 mg-1 at 37 degrees C and pH 7.8 and the monofunctional enzyme was oxygen stable, but the presence of a detergent proved to be essential for its stability.
Abstract: The 5,10-methenyltetrahydromethanopterin cyclohydrolase from Methanosarcina barkeri was purified 313-fold to a specific activity of 470 mumol min-1 mg-1 at 37 degrees C and pH 7.8. At this stage, the enzyme was pure as judged from polyacrylamide gel electrophoresis. The monofunctional enzyme was oxygen stable, but the presence of a detergent proved to be essential for its stability. Like the cyclohydrolase purified from Methanobacterium thermoautotrophicum (A. A. Dimarco, M. I. Donnelly, and R. S. Wolfe, J. Bacteriol. 168:1372-1377, 1986), the protein showed an apparent Mr of 82,000, and it is composed of two identical subunits as was concluded from nondenaturating and denaturating polyacrylamide gel electrophoresis. The enzymes from M. thermoautotrophicum and M. barkeri markedly differ with respect to the hydrolysis product of 5,10-methenyltetrahydromethanopterin: 5-formyl- and 10-formyltetrahydromethanopterin, respectively. The apparent Km for 5,10-methenyltetrahydromethanopterin was 0.57 mM at 37 degrees C and pH 7.8.

33 citations

Journal ArticleDOI
TL;DR: Out of five methanogens studied, only Methanococcus deltae and Methanocardium thermolithotrophicus could transform the nitroaromatic compounds; however, the transformation rates were significantly less than that of the new isolate Methanitis sp.
Abstract: The transformation of several nitroaromatic compounds by a newly isolated methanogenic bacterium, Methanococcus sp. (strain B) was studied. The presence of nitroaromatic compounds (0.5 mM) viz., nitrobenzene, 2,4-dinitrobenzene, 2,4,6-trinitrobenzene, 2,4-dinitrophenol, 2,4-dinitrobenzene, and 2,6-dinitrotoluene in the culture medium did not inhibit growth of the isolate. The bacteria grew rapidly and reached stationary phase within seven days of incubation. All the nitroaromatic compounds tested were 80 to 100% transformed by the bacterium to amino compounds by a reduction process. The isolate did not use the nitroaromatic compounds as the sole source of carbon or nitrogen. The transformation of nitroaromatic compounds by this isolate was compared to that of other methanogenic bacteria. Out of five methanogens studied, only Methanococcus deltae and Methanococcus thermolithotrophicus could transform the nitroaromatic compounds; however, the transformation rates were significantly less than that of the new isolate Methanococcus sp. (strain B). The nitroaromatic compounds were not transformed by Methanosarcina barkeri, Methanobacterium thermoautotrophicum, and Methanobrevibacter ruminantium.

33 citations

Journal ArticleDOI
TL;DR: It is proposed that such a distinction between the two enzymes in tRNASer identity determinants reflects their evolutionary pathways, hence attesting to their diversity.

33 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20237
202212
202112
202012
20197
201818