Methanofollis formosanus sp. nov., isolated from a fish pond

Abstract

A mesophilic, hydrogenotrophic methanogen, strain ML15T, was isolated from an aquaculture fish pond near Wang-gong, Taiwan. The cells were irregular cocci, non-motile, 1·5–2·0 μm in diameter and Gram-negative. Cells of strain ML15Tlysed easily in the presence of SDS (0·1 g l−1) and the S-layer protein had anMrof 138 800. The catabolic substrates utilized by this strain included formate and H2/CO2, but not acetate, methanol, trimethylamine or secondary alcohols. Growth did not occur in minimal medium, but was observed when yeast extract and tryptone were added. Strain ML15Tgrew fastest at 37 °C, pH 6·6–7·0 and with 3 % NaCl. Acetate was not required for cell growth. Trace amounts of tungstate promoted cell growth. The G+C contents of DNA ofMethanofollis aquaemarisN2F9704Tand strain ML15Twere 59·1 and 58·4 mol%, respectively. Sequence analysis of the 16S rRNA genes of strain ML15Tand selectedMethanofollisspecies revealed similarities of 95–97 %. Based on the data presented here, it is proposed that strain ML15T(=OCM 789T=DSM 15483T) represents a novel species,Methanofollis formosanussp. nov.