Reclassification of Methanogenium tationis and Methanogenium liminatans asMethanofollis tationis gen. nov., comb. nov. and Methanofollis liminatans comb. nov. and description of a new strain of Methanofollis liminatans

Sequencing of 16S rRNA genes and phylogenetic analysis of Methanogenium tat ionis DSM 2702(T) (OCM 43(T)) (T = type strain) and Methanogenium liminatan s GKZPZ(T) (= DSM 4140(T)) as well as other members of the family Methanomi crobiaceae revealed that both species belong to a separate line of descent within this family. In addition, a new strain of Methanogenium liminatans, strain BM1 (= DSM 10196). was isolated from a butyrate-degrading, fluidized bed reactor and characterized. Cells of both species are mesophilic, highl y irregular cocci that use H-2/CO2 and formate for growth and methanogenesi s. In addition, Methanogenium liminatans strains GKZPZ(T) and BM1 used 2-pr opanol/CO2, 2-butanol/CO2 and cyclopentanol/CO2. Both species contained die ther and tetraether lipids. The polar lipids comprised amino-phosphopentane tetrol derivatives, which appear to be characteristic lipids within the fam ily Methanomicrobiaceae. The pattern of glycolipids, phosphoglycolipids and amino-phosphoglycolipids was consistent with the assignment of these two s pecies to a taxon within the family Methanomicrobiaceae, but also permitted them to be distinguished from other higher taxa within this family. The GC contents of the DNA of Methanogenium tationis and Methanogenium liminatan s were 54 and 60 mol% (T-m and HPLC), respectively. On the basis of the dat a presented, transfer of Methanogenium tationis and Methanogenium liminatan s to the genus Methanofollis gen, nov. as Methanofollis tationis comb. nov. and Methanofollis liminatans comb. nov., respectively, is proposed, with M ethanofollis tationis as the type species.