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