Peter Schönheit

Different Ks values for hydrogen of methanogenic bacteria and sulfate reducing bacteria: An explanation for the apparent inhibition of methanogenesis by sulfate

Desulfovibrio vulgaris (Marburg) and Methanobrevibacter arboriphilus (AZ) are anaerobic sewage sludge bacteria which grow on H2 plus sulfate and H2 plus CO2 as sole energy sources, respectively. Their apparent Ks values for H2 were determined and found to be approximately 1 μM for the sulfate reducing bacterium and 6 μM for the methanogenic bacterium. In mixed cell suspensions of the two bacteria (adjusted to equal Vmax) the rate of H2 consumption by D. vulgaris was five times that of M. arboriphilus, when the hydrogen supply was rate limiting. The apparent inhibition of methanogenesis was of the same order as expected from the different Ks values for H2. Difference in substrate affinities can thus account for the inhibition of methanogenesis from H2 and CO2 in sulfate rich environments, where the H2 concentration is well below 5 μM.

Nickel, cobalt, and molybdenum requirement for growth of Methanobacterium thermoautotrophicum

Growth of Methanobacterium thermoautotrophicum on H2 and CO2 as sole energy and carbon sources was found to be dependent on Ni, Co, and Mo. At low concentrations of Ni (<100 nM), Co (<10 nM) and Mo (<10 nM) the amount of cells formed was roughly proportional to the amount of transition metal added to the medium; for the formation of 1 g cells (dry weight) approximately 150 nmol NiCl2, 20 nmol CoCl2 and 20 nmol Na2MoO4 were required. A dependence of growth on Cu, Mn, Zn, Ca, Al, and B could not be demonstrated. Conditions are described under which the bacterium grew exponentially with a doubling time of 1.8 h up to a cell density of 2 g cells (dry weight)/1.

Kinetic mechanism for the ability of sulfate reducers to out-compete methanogens for acetate

Methanosarcina barkeri and Desulfobacter postgatei are ubiquitous anaerobic bacteria which grow on acetate or acetate plus sulfate, respectively, as sole energy sources. Their apparent Ks values for acetate were determined and found to be approximately 0.2 mM for the sulfate-reducing bacterium and 3 mM for the methanogenic bacterium. In mixed cell suspensions of the two bacteria (adjusted to equal Vmax) the rate of acetate consumption by D. postgatei approached 15-fold the rate of M. barkeri at low acetate concentrations. The apparent inhibition of methanogenesis was of the same order as expected from the different Ks value for acetate. Difference in substrate affinities can thus account for the inhibition of methanogenesis from acetate in sulfate-rich environments, where the acetate concentration is well below 1 mM.

Growth parameters (Ks, μmax, Ys) of Methanobacterium thermoautotrophicum

AbstractMethanobacterium thermoautotrophicum was grown on a mineral salts medium in a fermenter gassed with H2 and CO2, which were the sole carbon and energy sources. Under the conditions used the bacterium grew exponentially. The dependence of the growth rate (μ) on the concentration of H2 and CO2 in the incoming gas and the dependence of the growth yield (

A rapid procedure for the purification of ferredoxin from Clostridia using polyethyleneimine.

Y_{CH_4 }

ATP formation coupled to caffeate reduction by H2 in Acetobacterium woodii NZva16

) on the growth rate were determined at pH 7 (the pH optimum) and 65° C (the temperature optimum).The curves relating growth rate to the H2 and CO2 concentration were hyperbolic. From reciprocal plots apparent Ks values for H2 and CO2 and μmax were obtained: app.

Studies on the biosynthesis of coenzyme F420 in methanogenic bacteria

K_{{\text{H}}_{\text{2}} }