Polynucleobacter is a genus of Proteobacteria, originally established by Heckmann and Schmidt (1987)[1] to exclusively harbor obligate endosymbionts of ciliates belonging to the genus Euplotes.

Scientific classification
Heckmann & Schmidt 1987,
emend. Hahn et al. 2009,
emend. Hahn et al. 2016
Type species
Polynucleobacter necessarius

P. acidiphobus Hahn et al. 2011
P. aenigmaticus Hahn et al. 2017
P. asymbioticus Hahn et al. 2016
P. campilacus Hahn et al. 2018
P. cosmopolitanus Hahn et al. 2010
P. difficilis Hahn et al. 2012
P. duraquae Hahn et al. 2016
P. hirudinilacicola Hahn et al. 2018
P. meluiroseus Pitt et al. 2018
P. necessarius Heckm. & Sch. 1987
P. paneuropaeus Hoetzi. et al. 2019
P. rarus Hahn et al. 2011
P. sinensis Hahn et al. 2016
P. sphagniphilus Hahn et al. 2017
P. victoriensis Hahn et al. 2017
P. wuianus Hahn et al. 2017
P. yangtzensis Hahn et al. 2016

Recently, several new Polynucleobacter species were described,[2][3][4][5][6][7][8][9] which all represent free-living (i.e. not host-associated) planktonic freshwater bacteria. Thus, the genus Polynucleobacter currently includes one species containing obligate endosymbionts of ciliates and nine species representing free-living planktonic strains. The type strains of the planktonic species were isolated from freshwater systems located in Armenia, Austria, China, France, Germany, Norway, Uganda, and the United States. Currently, the genus harbors 17 species.

Free-living Poynucleobacter bacteria represent important members of bacterioplankton in freshwater systems such as lakes, ponds, and streams.[10]


Two genome projects are finished on P. necessarius strains: one project on an obligately freeliving strain isolated from an acidic freshwater pond,[11] and one project on an obligate endosymbiont of the ciliate Euplotes aediculatus.[12]

Analyses of the genome sequences resulted in the discovery of a conserved RNA motif.


  1. ^ Heckmann, K. and H. J. Schmidt (1987) Polynucleobacter necessarius gen. nov., sp. nov., an obligately endosymbiotic bacterium living in the cytoplasm of Euplotes aediculatus. Int. J. Syst. Bacteriol. 37:456-457. (doi: 10.1099/00207713-37-4-456)
  2. ^ Hahn, M.W., E. Lang, U. Brandt, H. Lünsdorf, Q. L. Wu, and E. Stackebrandt (2010) Polynucleobacter cosmopolitanus sp. nov., free-living planktonic bacteria inhabiting freshwater lakes and rivers. Int. J. Syst. Evol. Microbiol. 60:166-173. (doi:10.1099/ijs.0.010595-0)
  3. ^ Hahn, M.W., E. Lang, U. Brandt, and C. Spröer (2011) Polynucleobacter acidiphobus sp. nov., a representative of an abundant group of planktonic freshwater bacteria. Int. J. Syst. Evol. Microbiol. 61:788-794. (doi:10.1099/ijs.0.023929-0)
  4. ^ Hahn, M.W., E. Lang, M. Tarao, and U. Brandt (2011) Polynucleobacter rarus sp. nov., a free-living planktonic bacterium isolated from an acidic lake. Int. J. Syst. Evol. Microbiol. 61:781-787 (doi:10.1099/ijs.0.017350-0)
  5. ^ Hahn, M.W., A. Minasyan, E. Lang, U. Koll, and C. Spröer (2012) Polynucleobacter difficilis sp. nov., a planktonic freshwater bacterium affiliated with subclustr B1 of the genus Polynucleobacter. Int. J. Syst. Evol. Microbiol. 62:376-383. (doi:10.1099/ijs.0.031393-0)
  6. ^ Hahn, M.W., J. Schmidt, A. Pitt, S.J. Taipale, and E. Lang (2016) Reclassification of four Polynucleobacter necessarius strains as representatives of Polynucleobacter asymbioticus comb. nov., Polynucleobacter duraquae sp. nov., Polynucleobacter yangtzensis sp. nov. and Polynucleobacter sinensis sp. nov., and emended description of Polynucleobacter necessarius. Int. J. Syst. Evol. Microbiol. 66: 2883-2892. (doi: 10.1099/ijsem.0.001073)
  7. ^ Hahn, M.W., L.R. Huymann, U. Koll, J. Schmidt, E. Lang, M. Hoetzinger (2017) Polynucleobacter wuianus sp. nov., a free-living freshwater bacterium affiliated with the cryptic species complex PnecC. Int. J. Syst. Evol. Microbiol. 67: 379-385. (doi: 10.1099/ijsem.0.001637)
  8. ^ Pitt A., Schmidt J., Lang E., Whitman W.B., Woyke T., Hahn M. W. (2018). Polynucleobacter meluiroseus sp. nov., a bacterium isolated from a lake located in the mountains of the Mediterranean island of Corsica. Int. J. Syst. Evol. Microbiol. 68: 1975-1985 [1]
  9. ^ Hoetzinger M., Schmidt J., Pitt A., Koll U., Lang E., Hahn M.W. (2019) Polynucleobacter paneuropaeus sp. nov., characterized by six strains isolated from freshwater lakes located along a 3000 km north-south cross-section across Europe. Int. J. Syst. Evol. Microbiol. 69:203-213. (doi: 10.1099/ijsem.0.003130)
  10. ^ Jezberová, J., J. Jezbera, U. Brandt, E.S. Lindström, S. Langenheder, and M.W. Hahn (2010). Ubiquity of Polynucleobacter necessarius ssp. asymbioticus in lentic freshwater habitats of a heterogenous 2000 km2 area. Environ. Microbiol. 12 : 658-669.
  11. ^ GOLD CARD: Gc00537 Genome project: Polynucleobacter necessarius subsp. asymbioticus QLW-P1DMWA-1, GOLD - Genomes OnLine Database
  12. ^ GOLD CARD: Gc00757 Genome project: Polynucleobacter necessarius subsp. necessarius STIR1, GOLD - Genomes OnLine Database

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