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An alder root nodule gall.JPG
An alder root nodule.
Scientific classification e
Domain: Bacteria
Phylum: Actinobacteria
Class: Actinobacteria
Order: Frankiales
Family: Frankiaceae
Genus: Frankia
Brunchorst, 1886[1]

Frankiella Maire and Tison 1909

Frankia is a genus of nitrogen-fixing, filamentous bacteria that live in symbiosis with actinorhizal plants, similar to the Rhizobium bacteria found in the root nodules of legumes in the family Fabaceae. Bacteria of this genus also initiate the forming of root nodules.

This genus was originally named by Jørgen Brunchorst in 1886 to honor the German biologist, Albert Bernhard Frank.[4] Brunchorst considered the organism he had identified to be a filamentous fungus. Becking [de; nl] redefined the genus in 1970 as containing prokaryotic actinomycetes and created the family Frankiaceae within the Actinomycetales. He retained the original name of Frankia for the genus.[5]

A section through an alder root nodule


Most Frankia strains are specific to different plant species. The bacteria are filamentous and convert atmospheric nitrogen into ammonia via the enzyme nitrogenase, a process known as nitrogen fixation. They do this while living in root nodules on actinorhizal plants. The bacteria can supply most or all of the nitrogen requirements of the host plant. As a result, actinorhizal plants colonise and often thrive in soils that are low in plant nutrients.[6]

Several Frankia genomes are now available which may help clarify how the symbiosis between prokaryote and plant evolved, how the environmental and geographical adaptations occurred, the metabolic diversity, and the horizontal gene flow among the symbiotic prokaryotes.[6] Research is proving that in low concentration Frankia can resist heavy metals such as, Cu, Co, and Zn.[7]

Symbiont plants[edit]


  1. ^ Brunchorst, J. "Uber einige Wurzelanschwellungen, besonders diejenigen von Alnus und den Elaegnaceen." Botanische Institut Tubingen (1886) 2:151-177.
  2. ^ Normand P, Nguyen TV, Battenberg K, Berry AM, Heuvel BV, Fernandez MP, Pawlowski K. (2017). "Proposal of 'Candidatus Frankia californiensis', the uncultured symbiont in nitrogen-fixing root nodules of a phylogenetically broad group of hosts endemic to western North America". Int J Syst Evol Microbiol. 67 (10): 3706–3715. doi:10.1099/ijsem.0.002147. PMID 28884663.CS1 maint: Uses authors parameter (link)
  3. ^ Normand P, Nouioui I, Pujic P, Fournier P, Dubost A, Schwob G, Klenk HP, Nguyen A, Abrouk D, Herrera-Belaroussi A, Pothier JF, Pflüger V, Fernandez MP. (2018). "Frankia canadensis sp. nov., isolated from root nodules of Alnus incana subspecies rugosa". Int J Syst Evol Microbiol. 68 (9): 3001–3011. doi:10.1099/ijsem.0.002939. PMID 30059001.CS1 maint: Uses authors parameter (link)
  4. ^ Pawlowski, Katharina (2009-06-17). Prokaryotic Symbionts in Plants. Springer Science & Business Media. p. 107. ISBN 9783540754602.
  5. ^ Frankia taxonomy
  6. ^ a b Frankia and Actinorhizal Plants
  7. ^ Abdel‐lateif, Khalid Salah El dein; Mansour, Samira R.; El‐Badawy, Mohamed F.; Shohayeb, Mohamed M. (2018). "Isolation and molecular characterization of Frankia strains resistant to some heavy metals". Journal of Basic Microbiology. 58 (9): 720–729. doi:10.1002/jobm.201800122. ISSN 1521-4028.
  8. ^ Schwintzer & Tjepkema 1990

External links[edit]