SOME CHARACTERISTICS OF 2 MORPHOTYPES OF METHANOTHRIX-SOEHNGENII FROM MESOPHILIC ANAEROBIC DIGESTERS

Six strains of acetotrophic methanogens, identified as Methanothrix soehngenii, were highly purified from mesophilic anaerobic digesters and their properties were investigated in comparison with a type strain M. soehngenii Opfikon. All strains were filamentous, exclusively acetotrophic, electrophoretically identical and had the same values for guanine plus cytosine content. However, two of them, one of which originated from an up-flow anaerobic sludge blanket (UASB), were remarkably filamentous and a number of filaments aggregated to form a cotton-like floc. In contrast with these strains, the others formed shorter filaments which were dispersed homogeneously. These indicate that two types of Methanothrix exist in anaerobic digesters. © 1990.