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 "Gammaproteobacteria" Garrity et al., 2005 [monotypic]
                 Class Gammaproteobacteriaᵀ Garrity et al. 2005
                   Order "Enterobacteriales" Garrity and Holt 2001 nom. nud. [monotypic]
                     Family Enterobacteriaceaeᵀ Rahn 1937 (Approved Lists 1980)
                       Genus Citrobacter Werkman and Gillen 1932 (Approved Lists 1980)
                         01 Citrobacter amalonaticus (Young et al. 1971) Brenner and Farmer 1982
                         02 Citrobacter braakii Brenner et al. 1993
                         03 Citrobacter farmeri Brenner et al. 1993
                         04 Citrobacter freundii (Braak 1928) Werkman and Gillen 1932 (Approved Lists 1980)
                         05 Citrobacter gillenii Brenner et al. 2000
                         06 Citrobacter koseri Frederiksen 1970 (Approved Lists 1980)
                         07 Citrobacter murliniae Brenner et al. 2000
                         08 Citrobacter rodentium Schauer et al. 1996
                         09 Citrobacter sedlakii Brenner et al. 1993
                         10 Citrobacter werkmanii Brenner et al. 1993
                         11 Citrobacter youngae Brenner et al. 1993