Domain Bacteria Woese et al. 1990
   Phylum Firmicutes corrig. Gibbons and Murray 1978 (Approved Lists 1980)
     Class "Clostridia" Garrity et al. 2001 nom. ined. see Class Clostridia Rainey 2010
       Order Clostridiales Prévot 1953 (Approved Lists 1980)
         Family "Peptostreptococcaceae" see Family Peptostreptococcaceae Ezaki 2010
           Genus Filifactor Collins et al. 1994
           Genus Fusibacter Ravot et al. 1999
           Genus Helcococcus Collins et al. 1993
           Genus Tissierella Collins and Shah 1986
           1 Genus Peptostreptococcus Kluyver and van Niel 1936 (Approved Lists 1980)