TRANSFER OF METHANOGENIUM-BOURGENSE, METHANOGENIUM-MARISNIGRI, METHANOGENIUM-OLENTANGYI, AND METHANOGENIUM-THERMOPHILICUM TO THE GENUS METHANOCULLEUS GEN-NOV, EMENDATION OF METHANOCULLEUS-MARISNIGRI AND METHANOGENIUM, AND DESCRIPTION OF NEW STRAINS OF METHANOCULLEUS-BOURGENSE AND METHANOCULLEUS-MARISNIGRI

Two strains of Methanogenium bourgense, strains MS2(T) (T = type strain) and LX1, were characterized, and, based in part on previously published DNA hybridization data, this species was transferred to a new genus, Methanoculleus, as Methanoculleus bourgense comb. nov. Methanogenium marisnigri JR1(T) and a new strain of Methanogenium marisnigri, strain AN8, were also characterized. This species was also transferred to the genus Methanoculleus as Methanoculleus marisnigri comb. nov. et emend., and its description was emended to indicate that the species has a temperature optimum near 40°C, is halotolerant, and is slightly alkaliphilic; in contrast, the previous description of this organism indicates that it has a temperature optimum of 20 to 25°C, is halophilic, and is slightly acidophilic. We also propose the transfer of two other phylogenetically related species, Methanogenium thermophilicum and Methanogenium olentangyi, to the genus Methanoculleus as Methanoculleus thermophilicum and Methanoculleus olentangyi, respectively. Methanogenium cariaci JR1(T) was also further characterized, and its description is emended.