plantenrijk Haeckel (1866) - plants
   [Division] Protophyta Sachs 1874 - primitive plants
     Class Schizomycetes Nägeli 1857 (Approved Lists 1980) - bacteria and related forms
       Order Pseudomonadales Orla-Jensen 1921 (Approved Lists 1980)
         Family Nitrobacteriaceae see Family Bradyrhizobiaceae Garrity et al. 2001 nom. ined.
           Genus Nitrobacter Winogradsky 1892 (Approved Lists 1980)