procaryotes Domain Archaea Woese et al. 1990 Phylum Euryarchaeota Garrity and Holt 2001 Class Methanococci Boone 2001 nom. inval. see Class Methanococci Boone 2002 Order Methanomicrobiales Balch and Wolfe 1981 Family Methanomicrobiaceae Balch and Wolfe 1981 1 Genus Methanomicrobium Balch and Wolfe 1981 2 Genus Methanoculleus MaestrojuƔn et al. 1990 3 Genus Methanofollis Zellner et al. 1999 4 Genus Methanogenium Romesser et al. 1981 5 Genus Methanolacinia Zellner et al. 1990 6 Genus Methanoplanus Wildgruber et al. 1984