Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         [crown] Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
           Domain Bacteria Woese et al. 1990 [paraphyletic?]
             Superphylum "Proteobacteria" Craig et al. 2010
               Phylum "Alphaproteobacteria" Garrity et al., 2006 [monotypic]
                 Class Alphaproteobacteriaᵀ Garrity et al. 2006
                   Order Rhizobiales Kuykendall 2006
                     Family Brucellaceae Breed et al. 1957 (Approved Lists 1980)
                       Genus Paenochrobactrum Kämpfer et al. 2010
                         1 Paenochrobactrum gallinariiᵀ Kämpfer et al. 2010
                         2 Paenochrobactrum glaciei (Romanenko et al. 2008) Kämpfer et al. 2010
                         3 Paenochrobactrum pullorum Kämpfer et al. 2014