METHANOGENESIS AT LOW-TEMPERATURES BY MICROFLORA OF TUNDRA WETLAND SOIL

Active methanogenesis from organic matter contained in soil samples fr om tundra wetland occurred even at 6 degrees C. Methane was the only e nd product in balanced microbial community with H-2/CO2 as a substrate , besides acetate was produced as an intermediate at temperatures belo w 10 degrees C. The activity of different microbial groups of methanog enic community in the temperature range of 6-28 degrees C was investig ated using 5% of tundra soil as inoculum. Anaerobic microflora of tund ra wetland fermented different organic compounds with formation of hyd rogen, volatile fatty acids (VFA) and alcohols. Methane was produced a t the second step. Homoacetogenic and methanogenic bacteria competed f or such substrates as hydrogen, formate, carbon monoxide and methanol. Acetogens out competed methanogens in an excess of substrate and low density of microbial population. Kinetic analysis of the results confi rmed the prevalence of hydrogen acetogenesis on methanogenesis. Pure c ulture of acetogenic bacteria was isolated at 6 degrees C. Dilution of tundra soil and supply with the excess of substrate disbalanced the m ethanoigenic microbial community. It resulted in accumulation of aceta te and other VFA. In balanced microbial community obviously autotrophi c methanogens keep hydrogen concentration below a threshold for syntro phic degradation of VFA. Accumulation of acetate- and H-2/CO2-utilisin g methanogens should be very important in methanogenic microbial commu nity operating at low temperatures.