Alphaproteobacteria Garrity et al. 2006 Caulobacterales Henrici and Johnson 1935 (Approved Lists 1980) Universal Root Woese et al. 1990 Bacteria (None 2015) Woese et al. 1990 Proteobacteria (sic) Garrity et al. 2021 Pseudomonadota corrig. Garrity et al. 2021 Alphaproteobacteriota (sic) Garrity et al. 2021 Alphaproteobacteria Garrity et al. 2006 Proteobacteria (sic) Garrity et al. 2021 Pseudomonadota corrig. Garrity et al. 2021 Alphaproteobacteriota (sic) Garrity et al. 2021 Gammaproteobacteria Garrity et al. 2005 emend. Williams and Kelly 2013 Betaproteobacteria Garrity et al. 2006 emend. Boden et al. 2017 Deltaproteobacteria Kuever et al. 2006 emend. Hahn et al. 2017 Epsilonproteobacteria Garrity et al. 2006 Zetaproteobacteria (sic) Makita et al. 2017 Mariprofundia corrig. Makita et al. 2017 Acidithiobacillia Williams and Kelly 2013 Oligoflexia Nakai et al. 2014 emend. Waite et al. 2020 Hydrogenophilalia Boden et al. 2017 Deltabacteria Cavalier-Smith 2002 Parvularculales Garrity et al. 2003 Rhizobiales Kuykendall 2006 Kordiimonadales Kwon et al. 2005 emend. Hördt et al. 2020 Rhodospirillales Pfennig and Trüper 1971 (Approved Lists 1980) emend. Hördt et al. 2020 Rickettsiales Gieszczykiewicz 1939 (Approved Lists 1980) emend. Dumler et al. 2001 Rhodobacterales Garrity et al. 2006 emend. Hördt et al. 2020 Sphingomonadales Yabuuchi and Kosako 2006 emend. Hördt et al. 2020 Caulobacterales Henrici and Johnson 1935 (Approved Lists 1980) Sneathiellales Kurahashi et al. 2008 Kiloniellales Wiese et al. 2009 Hyphomicrobiales Douglas 1957 (Approved Lists 1980) emend. Hördt et al. 2020 Incertae sedis 23 None 2015 Magnetococcales Bazylinski et al. 2013 Incertae sedis 91 None 2015 Incertae sedis 136 None 2015 Incertae sedis 154 None 2015 Incertae sedis 120 Tirandaz et al. 2015 Iodidimonadales Iino et al. 2016 Emcibacterales Iino et al. 2016 Micropepsales Harbison et al. 2017 Rhodothalassiales Venkata Ramana et al. 2014 Incertae sedis 70 None 2015 Incertae sedis 224 Kragelund et al. 2006 Incertae sedis 221 Kragelund et al. 2006 Incertae sedis 263 Kwan et al. 2012 Incertae sedis 265 Anderson and Haygood 2007 Incertae sedis 275 Bing et al. 2013 Incertae sedis 326 Horn et al. 1999 Pelagibacterales Grote et al. 2012 Minwuiales Sun et al. 2018 Holosporales Szokoli et al. 2020 Hyphomonadales Kevbrin et al. 2021 Maricaulales Kevbrin et al. 2021 Methylospongiales Podell et al. 2020 Incertae sedis 667 Kanamori et al. 2002 Tóth E.M. Vengring A. Homonnay Z.G. Kéki Zs. Spröer C. Borsodi A.K. Márialigeti K. Schumann P. Phreatobacter oligotrophus gen. nov., sp. nov., an alphaproteobacterium isolated from ultrapure water of the water purification system of a power plant 2014 64 3 839 845 International Journal of Systematic and Evolutionary Microbiology Int J Syst Evol Microbiol 1466-5026 1466-5034 10.1099/ijs.0.053843-0 24277862 Anderson C.M. Haygood M.G. Alpha-proteobacterial symbionts of marine bryozoans in the genus Watersipora. 2007 73 1 303 11 Applied and Environmental Microbiology Appl Environ Microbiol 0099-2240 1098-5336 10.1128/AEM.00604-06 17071786 Harbison A.B. Price L.E. Flythe M.D. Brauer S.L. Micropepsis pineolensis gen. nov., sp. nov., a mildly acidophilic alphaproteobacterium isolated from a poor fen, and proposal of Micropepsaceae fam. nov. within Micropepsales ord. nov. 2017 67 4 839 844 International Journal of Systematic and Evolutionary Microbiology Int J Syst Evol Microbiol 1466-5026 1466-5034 10.1099/ijsem.0.001681 27902348 Venkata Ramana V. Chakravarthy S.K. Ramaprasad E.V.V. Thiel V. Imhoff J.F. Sasikala Ch. Ramana Ch.V. Emended description of the genus Rhodothalassium Imhoff et al., 1998 and proposal of Rhodothalassiaceae fam. nov. and Rhodothalassiales ord. nov 2013 36 1 28 32 Systematic and Applied Microbiology Syst Appl Microbiol 0723-2020 10.1016/j.syapm.2012.09.003 23265196 Podell S. Blanton J.M. Oliver A. Schorn M.A. Agarwal V. Biggs J.S. Moore B.S. Allen E.E. A genomic view of trophic and metabolic diversity in clade-specific Lamellodysidea sponge microbiomes. 2020 8 1 97 97 Microbiome Microbiome 2049-2618 10.1186/s40168-020-00877-y 32576248 Sun C. Xu L. Yu X.-Y. Zhao Z. Wu Y.-H. Oren A. Wang C.-S. Xu X.-W. Minwuia thermotolerans gen. nov., sp. nov., a marine bacterium forming a deep branch in the Alphaproteobacteria, and proposal of Minwuiaceae fam. nov. and Minwuiales ord. nov. 2018 68 12 3856 3862 International Journal of Systematic and Evolutionary Microbiology Int J Syst Evol Microbiol 1466-5026 1466-5034 10.1099/ijsem.0.003073 30325296 Kanamori T. Rashid N. Morikawa M. Atomi H. Imanaka T. Oleomonas sagaranensis gen. nov., sp. nov., represents a novel genus in the alpha-Proteobacteria. 2002 217 2 255 261 FEMS Microbiology Letters FEMS Microbiol Lett 0378-1097 1574-6968 10.1111/j.1574-6968.2002.tb11484.x 12480113 Kwan J.C. Donia M.S. Han A.W. Hirose E. Haygood M.G. Schmidt E.W. Genome streamlining and chemical defense in a coral reef symbiosis. 2012 109 50 20655 60 Proceedings of the National Academy of Sciences of the United States of America Proc Natl Acad Sci U S A 0027-8424 1091-6490 10.1073/pnas.1213820109 23185008 Szokoli F. Castelli M. Sabaneyeva E. Schrallhammer M. Krenek S. Doak T.G. Berendonk T.U. Petroni G. Disentangling the Taxonomy of Rickettsiales and Description of Two Novel Symbionts ("Candidatus Bealeia paramacronuclearis" and "Candidatus Fokinia cryptica") Sharing the Cytoplasm of the Ciliate Protist Paramecium biaurelia. 2016 82 24 7236 7247 Applied and Environmental Microbiology Appl Environ Microbiol 0099-2240 1098-5336 10.1128/AEM.02284-16 27742680 Garrity G.M. Bell J.A. Lilburn T. Garrity G.M. Bell J.A. Lilburn T.G. Taxonomic outline of the Procaryotes 2003 4 1 39 Taxonomic Outline of the Procaryotes, Bergey's Manual of Systematic Bacteriology, Second Edition. Release 4.0 Springer-Verlag New York 10.1007/bergeysoutline200310 Bazylinski D.A. Williams T.J. Lefèvre C.T. Berg R.J. Zhang C.L. Bowser S.S. Dean A.J. Beveridge T.J. Magnetococcus marinus gen. nov., sp. nov., a marine, magnetotactic bacterium that represents a novel lineage (Magnetococcaceae fam. nov., Magnetococcales ord. nov.) at the base of the Alphaproteobacteria 2013 63 3 801 808 International Journal of Systematic and Evolutionary Microbiology Int J Syst Evol Microbiol 1466-5026 1466-5034 10.1099/ijs.0.038927-0 22581902 Horn M. Fritsche T.R. Gautom R.K. Schleifer K.H. Wagner M. Novel bacterial endosymbionts of Acanthamoeba spp. related to the Paramecium caudatum symbiont Caedibacter caryophilus. 1999 1 4 357 67 Environmental Microbiology Environ Microbiol 1462-2912 1462-2920 10.1046/j.1462-2920.1999.00045.x 11207753 Kragelund C. Kong Y. van der Waarde J. Thelen K. Eikelboom D. Tandoi V. Thomsen T.R. Nielsen P.H. Ecophysiology of different filamentous Alphaproteobacteria in industrial wastewater treatment plants. 2006 152 10 3003 12 Microbiology (Reading, England) Microbiology 1350-0872 1465-2080 10.1099/mic.0.29249-0 17005981 Paramasivam N. Ben-Dov E. Arotsker L. Kushmaro A. Eilatimonas milleporae gen. nov., sp. nov., a marine bacterium isolated from the hydrocoral Millepora dichotoma 2013 63 5 1880 1884 International Journal of Systematic and Evolutionary Microbiology Int J Syst Evol Microbiol 1466-5026 1466-5034 10.1099/ijs.0.043976-0 23002050 Tirandaz H. Dastgheib S.M.M. Amoozegar M.A. Shavandi M. De la Haba R.R. Ventosa A. Pseudorhodoplanes sinuspersici gen. nov., sp. nov., isolated from oil-contaminated soil 2015 65 12 4743 4748 International Journal of Systematic and Evolutionary Microbiology Int J Syst Evol Microbiol 1466-5026 1466-5034 10.1099/ijsem.0.000643 26420766 Suarez C. Ratering S. Geissler-Plaum R. Schnell S. Hartmannibacter diazotrophicus gen. nov., sp. nov., a novel phosphate-solubilizing and nitrogen-fixing alphaproteobacterium isolated from the rhizosphere of a natural salt-meadow plant 2014 64 9 3160 3167 International Journal of Systematic and Evolutionary Microbiology Int J Syst Evol Microbiol 1466-5026 1466-5034 10.1099/ijs.0.064154-0 24961682 Wiese J. Thiel V. Gärtner A. Schmaljohann R. Imhoff J.F. Kiloniella laminariae gen. nov., sp. nov., an alphaproteobacterium from the marine macroalga Laminaria saccharina. 2009 59 2 350 356 International Journal of Systematic and Evolutionary Microbiology Int J Syst Evol Microbiol 1466-5026 1466-5034 10.1099/ijs.0.001651-0 19196777 Romanenko L.A. Tanaka N. Svetashev V.I. Kalinovskaya N.I. Poseidonocella pacifica gen. nov., sp. nov. and Poseidonocella sedimentorum sp. nov., novel alphaproteobacteria from the shallow sandy sediments of the Sea of Japan 2012 194 113 121 Archives of Microbiology Arch Microbiol 0302-8933 1432-072X 10.1007/s00203-011-0736-3 21800148 Kevbrin V. Boltyanskaya Y. Koziaeva V. Uzun M. Grouzdev D. Alkalicaulis satelles gen. nov., sp. nov., a novel haloalkaliphile isolated from a laboratory culture cyanobacterium Geitlerinema species and proposals of Maricaulaceae fam. nov., Robiginitomaculaceae fam. nov., Maricaulales ord. nov. and Hyphomonadales ord. nov. 2021 71 1 International Journal of Systematic and Evolutionary Microbiology Int J Syst Evol Microbiol 1466-5026 1466-5034 10.1099/ijsem.0.004614 33351741 Bing X.-L. Yang J. Zchori-Fein E. Wang X.-W. Liu S.-S. Characterization of a newly discovered symbiont of the whitefly Bemisia tabaci (Hemiptera: Aleyrodidae). 2013 79 2 569 75 Applied and Environmental Microbiology Appl Environ Microbiol 0099-2240 1098-5336 10.1128/AEM.03030-12 23144129 Kwon K.K. Lee H.S. Yang S.H. Kim S.J. Kordiimonas gwangyangensis gen. nov., sp. nov., a marine bacterium isolated from marine sediments that forms a distinct phyletic lineage (Kordiimonadales ord. nov.) in the 'Alphaproteobacteria' 2005 55 5 2033 2037 International Journal of Systematic and Evolutionary Microbiology Int J Syst Evol Microbiol 1466-5026 1466-5034 10.1099/ijs.0.63684-0 16166706 Iino T. Ohkuma M. Kamagata Y. Amachi S. Iodidimonas muriae gen. nov., sp. nov., an aerobic iodide-oxidizing bacterium isolated from brine of a natural gas and iodine recovery facility, and proposals of Iodidimonadaceae fam. nov., Iodidimonadales ord. nov., Emcibacteraceae fam. nov. and Emcibacterales ord. nov. 2016 66 12 5016 5022 International Journal of Systematic and Evolutionary Microbiology Int J Syst Evol Microbiol 1466-5026 1466-5034 10.1099/ijsem.0.001462 27566239 Rappé M.S. Connon S.A. Vergin K.L. Giovannoni S.J. Cultivation of the ubiquitous SAR11 marine bacterioplankton clade 2002 418 630 633 Nature 0028-0836 1476-4687 10.1038/nature00917 12167859 Garrity G.M. Bell J.A. Lilburn T. Garrity G.M. Brenner D.J. Krieg N.R. Staley J.T. Class I. Alphaproteobacteria class. nov. 2005 2, Part C 2 1 Bergey's Manual of Systematic Bacteriology Springer New York 0387241450 Douglas H.C. Breed R.S. Murray E.G.D. Smith N.R. Order III. Hyphomicrobiales Douglas, ord. nov. 1957 7 276 Bergey's Manual of Determinative Bacteriology The Williams and Wilkins Co. Baltimore Kurahashi M. Fukunaga Y. Harayama S. Yokota A. Sneathiella glossodoripedis sp. nov., a marine alphaproteobacterium isolated from the nudibranch Glossodoris cincta, and proposal of Sneathiellales ord. nov. and Sneathiellaceae fam. nov. 2008 58 3 548 552 International Journal of Systematic and Evolutionary Microbiology Int J Syst Evol Microbiol 1466-5026 1466-5034 10.1099/ijs.0.65328-0 18319453