prokaryotes - bacteria see Domain Bacteria Woese et al. 1990
   Domain "Bacteria" Woese et al. 1990
     Phylum "Proteobacteria" Garrity et al. 2005 see Superphylum Proteobacteria Craig et al. 2010
       Class Betaproteobacteria Garrity et al. 2006
         1 Order "Procabacteriales" Garrity et al., 2003 [monotypic]
         2 Order Burkholderiales Garrity et al. 2006
         3 Order Hydrogenophilales Garrity et al. 2006 [monotypic]
         4 Order Methylophilales Garrity et al. 2006 [monotypic]
         5 Order Neisseriales Tønjum 2006
         6 Order Nitrosomonadales Garrity et al. 2006
         7 Order Rhodocyclales Garrity et al. 2006 [monotypic]
         8 Order Sulfuricellales Watanabe et al. 2015 [monotypic]
         9 Genus Chitinivorax Chen et al. 2012, incertae sedis