• Methane;
  • Methanotroph;
  • Diffusion;
  • Concentration gradient

Abstract A gel-stabilized system with counter gradients of CH4 and O2 was used to grow methanotrophs from wetland, agricultural and forest soils and lake sediment. Columns of semi-solid nitrate- or ammonium-minerai salts medium were continuously flushed at opposite ends with CH4 and O2 to create opposing concentration gradients of the two gases. Methanotrophs grew from all samples except forest soil, and were visible as thin bands after 5 to 15 days of incubation. The position of growth was CH4 and O2 concentration-dependent and occurred at the point of maximum possible CH4 oxidation, where both substrates were completely consumed. Evidence was obtained for denitrification and nitrification activities concomitant with CH4 oxidation. This approach may be useful to isolate methanotrophs with different CH4 and O2 requirements and to study their interactions with other groups of bacteria in nature.