[organisms] see Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
   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 Peptostreptococcus Kluyver and van Niel 1936 (Approved Lists 1980)
               Peptostreptococcus anaerobius (Natvig 1905) Kluyver and van Niel 1936 (Approved Lists 1980)