Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         Biota
           Domain Bacteria Woese et al. 1990
             Phylum "Spirochaetes" Garrity and Holt 2001 [monotypic]
               1 Class Spirochaetesᵀ Cavalier-Smith 2002 [monotypic]