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Appl Environ Microbiol. 1982 September; 44(3): 549-554
Copyright © 1982, American Society for Microbiology. All Rights Reserved.

Kinetics of Formate Metabolism in Methanobacterium formicicum and Methanospirillum hungatei

Department of Anaerobic Microbiology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061

ABSTRACT

The kinetics of formate metabolism in Methanobacterium formicicum and Methanospirillum hungatei were studied with log-phase formate-grown cultures. The progress of formate degradation was followed by the formyltetrahydrofolate synthetase assay for formate and fitted to the integrated form of the Michaelis-Menten equation. The K_m and V_max values for Methanobacterium formicicum were 0.58 mM formate and 0.037 mol of formate h^–1 g^–1 (dry weight), respectively. The lowest concentration of formate metabolized by Methanobacterium formicicum was 26 µM. The K_m and V_max values for Methanospirillum hungatei were 0.22 mM and 0.044 mol of formate h^–1 g^–1 (dry weight), respectively. The lowest concentration of formate metabolized by Methanospirillum hungatei was 15 µM. The apparent K_m for formate by formate dehydrogenase in cell-free extracts of Methanospirillum hungatei was 0.11 mM. The K_m for H₂ uptake by cultures of Methanobacterium formicicum was 6 µM dissolved H₂. Formate and H₂ were equivalent electron donors for methanogenesis when both substrates were above saturation; however, H₂ uptake was severely depressed when formate was above saturation and the dissolved H₂ was below 6 µM. Formate-grown cultures of Methanobacterium formicicum that were substrate limited for 57 h showed an immediate increase in growth and methanogenesis when formate was added to above saturation.