Class Proteobacteria Stackebrandt et al. 1988 nom. rej. see Phylum Proteobacteria Garrity and Holt 2001 nom. nud.
   Subclass alpha see Class Alphaproteobacteria "Garrity and Holt 2001" nom. nud.
     Group 4 see Order Sphingomonadales "Garrity and Holt 2001" nom. nud.
       Family Sphingomonadaceae Kosako et al. 2000
         Genus Porphyrobacter Fuerst et al. 1993 see Genus Erythrobacter Shiba and Simidu 1982