The 16S rRNA gene sequences of Halococcus saccharolyticus and Halococcus salifodinae were closely related (94·5–94–7% similarity) to that of Halococcus morrhuae, the type species of the genus Halococcus. However, Halococcus turkmenicus was distinct from the other members of this genus, with low 16S rRNA similarities when compared to Halococcus morrhuae (88·7%). On the basis of phylogenetic tree reconstruction, detection of signature bases and DNA-DNA hybridization data, it is proposed to transfer Halococcus turkmenicus to a novel genus, Haloterrigena, as Haloterrigena turkmenica gen. nov., comb, nov., and to accommodate Halobacterium trapanicum JCM 9743 and strain GSL-11 in the same species. On the basis of morphological, cultural and 16S rRNA sequence data, it is also proposed that the culture collection strains of Halobacterium trapanicum NCIMB 767, ATCC 43102 and JCM 8979 should be renamed as Halococcus sp.
Sequencing of 16S rRNA genes and phylogenetic analysis of Methanogenium tationis DSM 2702T(OCM 43T) (T = type strain) and Methanogenium liminatans GKZPZT(= DSM 4140T) as well as other members of the family Methanomicrobiaceaer 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, highly irregular cocci that use H2/CO2 and formate for growth and methanogenesis. In addition, Methanogenium liminatans strains GKZPZTTand BM1 used 2-propanol/CO2, 2-butanol/CO2 and cyclopentanol/CO2. Both species contained diether and tetraether lipids. The polar lipids comprised amino-phosphopentanetetrol derivatives, which appear to be characteristic lipids within the family Methanomicrobiaceae, The pattern of glycolipids, phosphoglycolipids and amino-phosphoglycolipids was consistent with the assignment of these two species to a taxon within the family Methanomicrobiaceae, but also permitted them to be distinguished from other higher taxa within this family. The G+C contents of the DNA of Methanogenium tationis and Methanogenium liminatans were 54 and 60 mol% (Tm and HPLC), respectively. On the basis of the data presented, the transfer of Methanogenium tationis and Methanogenium liminatans to the genus Methanofollis gen. nov. as Methanofollis tationis comb. nov. and Methanofollis liminatans comb. nov., respectively, is proposed, with Methanofollis tationis as the type species.
Two haloalkaliphilic archaea were isolated from a soda lake in Tibet. The two strains, designated A33Tand GA33T, were Gram-negative, pleomorphic, flat, non-motile and strictly aerobic. Growth required at least 12% NaCl. Growth was between pH 8·0 and pH 11 with an optimum at pH 9·0--9·5. Cells were chemo-organotrophic. Polar lipids were C20-C25 derivatives of phosphatidylglycerol and phosphatidylglycerol phosphate. The nucleotide sequences of the 16S rRNA genes from the two strains were obtained by the analysis of the cloned rDNAs. On 16S rRNA phylogenetic trees, the two strains formed a monophyletic cluster. They differed from their closest neighbours, Halobacterium trapanicum and Natrialba asiatica, in polar lipid composition, a well as physiological and phenotypic characteristics. DNA-DNA hybridization indicated that the two strains belonged to different species of the same genu. The results indicated that the strains A33Tand GA33Tshould be classified in a new genus Natronorubrum gen. nov. as Natronorubrum bangense sp. nov. (strain A33T) and Natronorubrum tibetense sp. nov. (strain GA33T).