Methanogenium liminatans spec. nov., a new coccoid,mesophilic methanogen able to oxidize secondary alcohols

A new mesophilic, coccoid methanogen, assigned as Methanogenium liminatans spec. nov. strain DSM 4140, was isolated from effluent of a reactor for the anaerobic treatment of industrial waste water. Cells of M. Liminatans formed irregular cocci, about 1.5 m in size, and occurred singly. The cell envelope was an S-layer with hexagonally arranged glycoprotein subunits (M_r=118000). The center-to-center spacings were 15.4 nm. The polar lipid pattern was similar to that of Methanogenium tationis, the polyamine content similar to that found in several Methanogenium species. Strain DSM 4140 grew with H₂/CO₂, formate, 2-propanol/CO₂, 2-butanol/CO₂ and cyclopentanol/CO₂. For growth with the different substrates acetate was required as an additional carbon source. Growth on H₂/CO₂ was stimulated by the addition of tungstate. The optimal concentration was 1–2 M Na₂WO₄. ¹⁸⁵WO_inf4^sup2-was incorporated into cells. Growth was not influenced by 0–600 mM NaCl, but no growth occurred in the presence of 800 mM NaCl. Increasing concentrations of KCl up to 100 mM were slightly inhibitory for growth. The optimal growth temperature was around 40°C. The G+C content of the DNA was 59.3 mol% (T_m) or 60.5 mol% (HPLC).Abbreviations HPLC = high performance liquid chromatography - PAS = periodic acid-Schiff reagent - sADH = secondary alcohol dehydrogenase - F₄₂₀ = 7,8-didemethyl-8-hydroxy-5-deazariboflavin