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 Thiotrichales Garrity et al. 2005
                     Family Piscirickettsiaceae Fryer and Lannan 2005
                       1 Genus Piscirickettsiaᵀ Fryer et al. 1992 [monotypic]
                       2 Genus Cycloclasticus Dyksterhouse et al. 1995 [monotypic]
                       3 Genus Galenea Giovannelli et al. 2012 [monotypic]
                       4 Genus Hydrogenovibrio Nishihara et al. 1991 [monotypic]
                       5 Genus Methylophaga Janvier et al. 1985
                       6 Genus Sulfurivirga Takai et al. 2006 [monotypic]
                       7 Genus Thioalkalimicrobium Sorokin et al. 2001
                       8 Genus Thiomicrospira Kuenen and Veldkamp 1972 (Approved Lists 1980)