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Citrobacter freundii (secondary electron microscope image)

Citrobacter freundii (secondary electron microscope image)

Classification : Creature
Domain : Bacteria (bacteria)
Department : Proteobacteria
Scientific name
Garrity et al. 2005

The Proteobacteria represent one of the larger groups of the domain of bacteria , which are regarded as divisions or as strains (in the sense of phylum ) . They include many important nitrogen-fixing bacteria and pathogens.

The name Proteobacteria is derived from the Greek god Proteus , who could change shape, and refers to the variety of shapes in this group. It is therefore not morphologically, but is defined by related RNA sequences. The cell walls of the Proteobacteria consist in particular of single-layer to single-layer murein and lipopolysaccharides , which is why they are gram-negative . However, some species also react gram-variable, such as B. Azospirillum brasilense and species of Methylobacterium . Many species have flagella , others are able to slide.

Some subgroups like the Rhodospirillaceae ( purple bacteria ) and Chromatiaceae (sulfur purple bacteria) are able to carry out anoxygenic photosynthesis under anoxic conditions . They use organic substances, hydrogen sulfide , sulfur or hydrogen as electron donors and therefore do not produce any elemental oxygen .

The subgroup of Myxobacteria is so far the only known group of proteobacteria in the transition field between the unicellular and multicellular way of life. Myxobacteria form multicellular fruiting bodies with spores, a convergence to the slime molds .

The Proteobacteria were initially divided into five main groups, which were viewed as a class , and were given the Greek letters Alpha to Epsilon as a prefix: Alphaproteobacteria , Betaproteobacteria , Gammaproteobacteria , Deltaproteobacteria and Epsilonproteobacteria . In the course of time, four other classes have been described (as of 2020), the " Zetaproteobacteria ", Acidithiobacillia , Hydrogenophilalia and Oligoflexia .

The mitochondria of the eukaryotes , all living things with a cell nucleus, possibly originate from endosymbiotic proteobacteria ( see: endosymbiotic hypothesis ).


Some important orders, families and genera of the eight classes of proteobacteria are listed below. The article Systematics of Bacteria is a reference in Wikipedia and contains a larger selection of taxa in the Phylum Proteobacteria.


  • Family Acidithiobacillaceae
  • Thermithiobacillaceae family


and other taxa


and other taxa


  • Order II. "Xanthomonadales"

Within the LPSN ( List of Prokaryotic names with Standing in Nomenclature ), an important listing of the bacterial systematics, the order Xanthomonadales is no longer listed. This order and the only delivered family Xanthomonadaceae have been dissolved due to recent investigations. Many of the genera are now assigned to the order Lysobacterales , others are not yet assigned to any special order. However, the old system is still in use. B. in the taxonomy database of the NCBI ( National Center for Biotechnology Information ), an important source for information on bacteria, is still used.

  • Order XII. Enterobacterales , previously referred to as the order "Enterobacteriales"
and other taxa


with only one genus, Hydrogenophilus


and other taxa


and other taxa


  • Order I. Oligoflexales
  • Oligoflexaceae family
  • Order II. Silvanigrellales
  • Silvanigrellalaceae

" Zetaproteobacteria "



  • Martin Dworkin, Stanley Falkow, Eugene Rosenberg, Karl-Heinz Schleifer, Erko Stackebrandt (Eds.): The Prokaryotes, A Handbook of the Biology of Bacteria . 7 volumes, 3rd edition, Springer-Verlag, New York et al. O., 2006, ISBN 0-387-30740-0 . Vol. 5: Proteobacteria: Alpha and Beta Subclass ISBN 0-387-30745-1 ; Vol. 6: Proteobacteria: Gamma Subclass ISBN 0-387-30746-X ; Vol. 7: Proteobacteria: Delta and Epsilon Subclass , ISBN 0-387-30747-8
  • George M. Garrity , Don J. Brenner , Noel R. Krieg, James T. Staley (Eds.): Bergey's Manual of Systematic Bacteriology: Volume 2: The Proteobacteria, Part B: The Gammaproteobacteria . 2nd Edition. Springer-Verlag, New York 2005, ISBN 978-0-387-95040-2 , doi : 10.1007 / 0-387-28022-7 .
  • George M. Garrity, Don J. Brenner, Noel R. Krieg, James T. Staley (Eds.): Bergey's Manual of Systematic Bacteriology: Volume 2: The Proteobacteria, Part C: The Alpha-, Beta-, Delta-, and Epsilonproteobacteria . 2nd Edition. Springer-Verlag, New York 2005, ISBN 978-0-387-24145-6 , doi : 10.1007 / 0-387-29298-5 .

Individual evidence

  1. a b Jean Euzéby, Aidan C. Parte: Classification of domains and phyla - Hierarchical classification of prokaryotes (bacteria). In: List of Prokaryotic names with Standing in Nomenclature, Systematics of Bacteria (LPSN) . Retrieved December 20, 2019 .
  2. KP Williams, DP Kelly: Proposal for a new class within the phylum Proteobacteria, Acidithiobacillia classis nov., With the type order Acidithiobacillales, and emended description of the class Gammaproteobacteria . In: International Journal of Systematic and Evolutionary Microbiology . No. 63 , August 2013, p. 2901-2906 , doi : 10.1099 / ijs.0.049270-0 .
  3. ^ BJ Tindall: The family name Solimonadaceae Losey et al. 2013 is illegitimate, proposals to create the names 'Sinobacter soli' comb. nov. and 'Sinobacter variicoloris' contravene the Code, the family name Xanthomonadaceae Saddler and Bradbury 2005 and the order name Xanthomonadales Saddler and Bradbury 2005 are illegitimate and notes on the application of the family names Solibacteraceae Zhou et al. 2008, Nevskiaceae Henrici and Johnson 1935 (Approved Lists 1980) and Lysobacteraceae Christensen and Cook 1978 (Approved Lists 1980) and order name Lysobacteriales Christensen and Cook 1978 (Approved Lists 1980) with respect to the classification of the corresponding type genera Solibacter Zhou et al . 2008, Nevskia Famintzin 1892 (Approved Lists 1980) and Lysobacter Christensen and Cook 1978 (Approved Lists 1980) and importance of accurately expressing the link between a taxonomic name, its authors and the corresponding description / circumscription / emendation In: International Journal of Systematic and Evolutionary Microbiology (IJSB) Volume 64, pp. 293-297. DOI: 10.1099 / ijs.0.057158-0
  4. M. Adeolu, S. Alnajar, S. Naushad, RS Gupta: Genome-based phylogeny and taxonomy of the 'Enterobacteriales': proposal for Enterobacterales ord. nov. divided into the families Enterobacteriaceae, Erwiniaceae fam. nov., Pectobacteriaceae fam. nov., Yersiniaceae fam. nov., Hafniaceae fam. nov., Morganellaceae fam. nov., and Budviciaceae fam. nov. In: International Journal of Systematic and Evolutionary Microbiology. No. 66 , December 2016, p. 5575-5599 , doi : 10.1099 / ijsem.0.001485 .
  5. R. Nakai, M. Nishijima, N. Tazato, Y. Handa, F. Karray, S. Sayadi, H. Isoda, T. Naganuma: Oligoflexus tunisiensis gen. Nov., Sp. nov., a Gram-negative, aerobic, filamentous bacterium of a novel proteobacterial lineage, and description of Oligoflexaceae fam. nov., Oligoflexales ord. nov. and Oligoflexia classis nov. In: International Journal of Systematic and Evolutionary Microbiology . No. 64 , October 2014, p. 3353-3359 , doi : 10.1099 / ijs.0.060798-0 .
  6. Martin W. Hahn, Johanna Schmidt, Ulrike Koll, Manfred Rohde, Susanne Verbarg, Alexandra Pitt, Ryosuke Nakai, Takeshi Naganuma, Elke Lang: Silvanigrella aquatica gen. Nov., Sp. nov., isolated from a freshwater lake, description of Silvanigrellaceae fam. nov. and Silvanigrellales ord. nov., reclassification of the order Bdellovibrionales in the class Oligoflexia, reclassification of the families Bacteriovoracaceae and Halobacteriovoraceae in the new order Bacteriovoracales ord. nov., and reclassification of the family Pseudobacteriovoracaceae in the order Oligoflexales . In: International Journal of Systematic and Evolutionary Microbiology . No. 67 , August 2017, p. 2555-2568 , doi : 10.1099 / ijsem.0.001965 .
  7. David Emerson, Jeremy A. Rentz, Timothy G. Lilburn, Richard E. Davis, Henry Aldrich, Clara Chan, Craig L. Moyer, Anna-Louise Reysenbach: A Novel Lineage of Proteobacteria Involved in Formation of Marine Fe-Oxidizing Microbial Mat Communities . In: PLoS ONE . tape 2 , no. 8 , August 2007, p. e667 , doi : 10.1371 / journal.pone.0000667 .

Web links

Commons : Proteobacteria  - collection of images, videos and audio files
 Wikispecies: Proteobacteria  - Species Directory