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 Gammaproteobacteria Garrity et al. 2005
         Order "Enterobacteriales" Garrity and Holt 2001 nom. nud. [monotypic]
           Family Enterobacteriaceae Rahn 1937 (Approved Lists 1980)
             Genus Levinea Young et al. 1971 (Approved Lists 1980) see Genus Citrobacter Werkman and Gillen 1932 (Approved Lists 1980)