Thermophilic Methanogenic Bacterium Research Articles

Sulphide inhibition of methanogenic activity at various pH levels at 55°C

AbstractThe purpose of this study was to evaluate the toxic effect of sulphide on thermophilic methanogenic bacteria, pre‐cultivated in UASB‐reactors fed with and without sulphate, at 55°C and different pH levels. For granular sludge, precultivated in the presence of sulphate, the inhibition caused by hydrogen sulphide was dependent on the pH imposed. At alkaline pH the inhibitory effect of hydrogen sulphide was higher than at neutral or acidic pH. The effect of sulphide could not be described in terms of free hydrogen sulphide level only. For dispersed sludge, pre‐cultivated in the absence of sulphate, the inhibition caused by free hydrogen sulphide was independent of the pH, and the toxic effect of sulphide could be described in terms of free hydrogen sulphide.

Kinetic studies of acetate fermentation by Methanosarcina sp. MSTA-1.

The effect of three parameters (initial acetate concentration, temperature and pH) on the acetoclastic reaction was studied with the thermophilic methanogenic bacterium Methanosarcina sp. MSTA-1. The optimum temperature for growth ranged around 55 degrees C, and optimum pH was 6.5-7.5, giving a minimum generation time of 12.6-13.9 h (mu max = 0.050-0.055 h-1) and a maximum value of the specific acetate consumption rate (qmaxs) of 14-20 mmol/g cells per hour. Contrary to the methane yield, the growth yield was found to be dependent on culture conditions, especially on incubation temperature. Methanosarcina sp. MSTA-1 showed a low affinity for acetate substrate. Growth at 55 degrees C and at constant pH 7 resulted in a Km value and a threshold acetate concentration of 10.7 mM and 0.7 mM, respectively.

Growth of Methanobacterium thermoautotrophicum on H 2CO 2: High CH 4 productivities in continuous culture

The thermophilic methanogenic bacterium, Methanobacterium thermoautotrophicum, was grown on H 2CO 2. In continuous culture, high CH 4 productivities were obtained (288 litres litre −1 day −1) with 96% CH 4 in the effluent gas, i.e. the productivity was twice as high as that obtained previously by other authors, with pure or mixed cultures; the biomass was 3·6 g dry wt litre −1.

Isolation and characterization of thermophilic methanogenic bacteria from mushroom compost

During the first stage of the preparation of mushroom compost oxygen is believed to be readily available. However we measured methane in the evoking air above the compost piles and were able to isolate thermophilic methanogenic bacteria from this compost. The isolates grow only on H 2 and CO 2 as energy and carbon source and do not require complex factors for growth. On the basis of nutritional and morphological characteristics these methanogens were identified as strains of Methanobacterium thermoautotrophicum.

Isolation and characterization of thermophilic methanogenic bacteria from mushroom compost

During the first stage of the preparation of mushroom compost oxygen is believed to be readily available. However we measured methane in the evoking air above the compost piles and were able to isolate thermophilic methanogenic bacteria from this compost. The isolates grow only on H2 and CO2 as energy and carbon source and do not require complex factors for growth. On the basis of nutritional and morphological characteristics these methanogens were identified as strains of Methanobacterium thermoautotrophicum.

Growth of Methanococcus thermolithotrophicus in batch and continuous culture on H2 and CO2: influence of agitation

A thermophilic methanogenic bacterium, Methanococcus thermolithotrophicus, was grown on H2 and CO2 in both batch and continuous culture, in a fermentor equipped with either a straight blade impeller or a Rushton impeller. Production was continued until 470 l CH4·l-1 per day was obtained with a biomass of 3.5 g dry wt. l-1 under batch conditions.

Sensitivity of thermophilic methanogenic bacteria to heavy metals

The effects of Cd, Cu, and Ni on pure cultures of thermophilic methanogenic bacteria were studied. The bacteria used wereMethanobacterium thermoautotrophicum and TAM, a thermophilic, acetate-decarboxylating, methanogenic bacterium. Much lower concentrations of heavy metals were needed to cause initial inhibition of TAM (1 mg/liter Cu and Cd; 5 mg/liter Ni) compared withM. thermoautotrophicum (10 mg/liter Cu and Cd; and 100 mg/liter Ni). No growth of TAM occurred at 5 mg/liter Cu and 25 mg/liter Ni, while the corresponding values forM. thermoautotrophicum were 50 mg/liter Cu and 200 mg/liter Ni. Cd (50 mg/liter) was totally inhibitory toM. thermoautotrophicum but allowed minimal growth of TAM. Ni stimulated both organisms at an optimal concentration of 5 mg/liter forM. thermoautotrophicum and 1 mg/liter for TAM. The toxicity of Cd and Cu was found to depend upon the presence of Ni in the medium.

Dinitrogen fixation by a thermophilic methanogenic bacterium.

Methanogenic bacteria are known to use NH+4 as a nitrogen source for growth. Previous work with an impure methanogenic culture suggested that a methanogen might fix atmospheric dinitrogen as a nitrogen source, but no further work on this phenomenon has been documented. We have now examined the use of N2 by Methanococcus thermolithotrophicus and find that the organism can grow well, with multiple transfers, in medium having N2 as the source of nitrogen. Control cultures without N2 and containing less than 0.1 mM NH+4 do not grow. Growth yields with N2 are on the average one-third those with NH+4, suggesting that, as in other nitrogen-fixing organisms, this bacterium requires a large amount of ATP for the reduction to occur. After growing in NH+4-containing medium, a long lag is observed before growth begins with N2 as the nitrogen source; the NH+4 levels must be very low for growth to begin. Cells grown in N2-fixing conditions reduce acetylene to ethylene. The discovery of a nitrogen-fixing archaebacterium has important implications for studies on the evolution of nitrogenase, and the fact that M. thermolithotrophicus nitrogenase is active at 64 degrees C suggests that a novel enzyme is involved.

Response of growth and methane production to limiting amounts of sulfide and ammonia in two thermophilic methanogenic bacteria

Response of growth and methane production to limiting amounts of sulfide and ammonia in two thermophilic methanogenic bacteria

Response of growth and methane production to limiting amounts of sulfide and ammonia in two thermophilic methanogenic bacteria

Response of growth and methane production to limiting amounts of sulfide and ammonia in two thermophilic methanogenic bacteria

Variation of the ATP-pool in thermophilic methanogenic bacteria during nitrogen or sulfur starvation

Variation of the ATP-pool in thermophilic methanogenic bacteria during nitrogen or sulfur starvation

Variation of the ATP-pool in thermophilic methanogenic bacteria during nitrogen or sulfur starvation

Variation of the ATP-pool in thermophilic methanogenic bacteria during nitrogen or sulfur starvation

Sulfide-Dependent Methane Production and Growth of a Thermophilic Methanogenic Bacterium

Two strains of a thermophilic methanogenic bacterium, designated MT1 a and b, were isolated from a coastal surface sediment in the northern part of the Swedish West Coast. The two strains were identical in appearance and nutritional requirements and resembled Methanobacterium thermoautotrophicum. MT1 had an extraordinary requirement for sulfide. At sulfide levels below 0.1 mM, growth was poor and the methane production rate decreased. Other sources of sulfur, such as cysteine, sulfate, or thiosulfate, could not replace sulfide. The results indicate that a fast turnover rate of reduced sulfur compounds is involved in the energy metabolism of this organism.

ATP hydrolysis and synthesis by the membrane-bound ATP synthetase complex of Methanobacterium thermoautotrophicum.

The membrane-bound ATP synthetase complex of Methanobacterium thermoautotrophicum showed maximum activity for ATP hydrolysis at pH 8, at temperatures between 65 and 70 degrees C, and at an ATP-Mg2+ ratio of 0.5. Anaerobic conditions were not prerequisite for enzyme activity. The enzyme showed a Km value for ATP of 2 mM, and activity was Mg2+ dependent; Mn2+, Co2+, Ca2+, and Zn2+ could replace Mg2+ to some extent. Other nucleoside triphosphates could be hydrolyzed. N,N'-dicyclohexylcarbodiimide inhibited ATP hydrolysis. A proton-motive force, artificially imposed by a pH shift or valinomycin, resulted in ATP synthesis in whole cells. The ATP synthetase complex of the thermophilic methanogenic bacterium is similar to those described in aerobic and anaerobic microorganisms.