Energetics and regulations of formate and hydrogen metabolism by Methanobacterium formicicum |
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Authors: | Wei-Min Wu Robert F Hickey Mahendra K Jain J Gregory Zeikus |
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Institution: | (1) Michigan Biotechnology Institute, 3900 Collins Road, 48 909 Lansing, Michigan, USA;(2) Department of Civil and Environmental Engineering, Michigan State University, 48824 East Lansing, Michigan, USA;(3) Department of Animal Science, Michigan State University, 48824 East Lansing, Michigan, USA;(4) Department of Biochemistry, Michigan State University, 48824 East Lansing, Michigan, USA;(5) Department of Microbiology and Public Health, Michigan State University, 48824 East Lansing, Michigan, USA |
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Abstract: | Accumulation of formate to millimolar levels was observed during the growth of Methanobacterium formicicum species on H2–CO2. Hydrogen was also produced during formate metabolism by M. formicicum. The amount of formate accumulated in the medium or the amount H2 released in gas phase was influenced by the bicarbonate concentration. The formate hydrogenlyase system was constitutive but regulated by formate. When methanogenesis was inhibited by addition of 2-bromoethane sulfonate, M. formicicum synthesized formate from H2 plus HCO
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or produced H2 from formate to a steady-state level at which point the Gibbs free energy (G) available for formate synthesis or H2 production was approximately -2 to -3 kJ/reaction. Formate conversion to methane was inhibited in the presence of high H2 pressure. The relative rates of conversion of formate and H2 were apparently controlled by the G available for formate synthesis, hydrogen production, methane production from formate and methane production from H2. Results from 14C-tracer tests indicated that a rapid isotopic exchange between HCOO- and HCO
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occurred during the growth of M. formicicum on H2–CO2. Data from metabolism of 14C-labelled formate to methane suggested that formate was initially split to H2 and HCO
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and then subsequently converted to methane. When molybdate was replaced with tungstate in the growth media, the growth of M. formicicum strain MF on H2–CO2 was inhibited although production of methane was not Formate synthesis from H2 was also inhibited. |
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Keywords: | Methanobacterium formicicum Formate metabolism Methanogenesis from formate Methanogenesis from H2 H2 metabolism |
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