View source for Frankia

{{Short description|Genus of bacteria}}
{{About|the filamentous bacteria|the Frankish empire|Francia|the plant|Gymnarrhena}}
{{Automatic taxobox
| taxon = Frankia
| image = An alder root nodule gall.JPG
| image_caption = An alder root nodule.
| parent_authority = Becking 1970 (Approved Lists 1980)<ref>{{cite journal | author = Becking JH. | title = ''Frankiaceae'' fam. nov. (''Actinomycetales'') with one new combination and six new species of the genus ''Frankia'' Brunchorst 1886, 174 | journal = International Journal of Systematic Bacteriology | year = 1970 | volume = 20 | pages = 201–220| doi = 10.1099/00207713-20-2-201 | doi-access = free }}</ref>
| authority = [[Jørgen Brunchorst|Brunchorst]] 1886<ref name=Brunchorst>{{cite journal | author = Brunchorst J. | title = Über einige Wurzelanschwellungen, besonders diejenigen von Alnus und den Elaegnaceen | trans-title = On root swellings, particularly those of ''Alnus'' and the ''Elaeagnaceae'' | journal = Untersuchungen aus dem botanischen Institut in Tübingen [Investigations of the Botanical Institute in Tübingen ] | year = 1886 | volume = 2 | issue = 151–177}}</ref>
| type_species = ''[[Frankia alni]]''
| type_species_authority = ([[Mikhail Stepanovich Voronin|Woronin]] 1866) [[Von Tubeuf]] 1895 non Steud. 1840
| subdivision_ranks = Species
| subdivision_ref = <ref name=LPSN/>
| subdivision = See text
| synonyms =
* ''Frankiella'' <small>[[René Maire|Maire]] and [[Adrien Tison|Tison]] 1909 non von Speschnew 1900 non Racheboeuf 1983</small>
* ''Parafrankia'' <small>Gtari 2023</small>
* ''Protofrankia'' <small>Gtari 2023</small>
* ''Pseudofrankia'' <small>Gtari 2023</small>
}}

'''''Frankia''''' is a genus of [[Nitrogen fixation|nitrogen-fixing]] [[Filamentation|bacteria]] that live in [[symbiosis]] with [[actinorhizal plant]]s, similar to the ''[[Rhizobium]]'' bacteria found in the root nodules of [[legume]]s in the family [[Fabaceae]]. ''Frankia'' also initiate the forming of [[root nodule]]s.

This genus was originally named by [[Jørgen Brunchorst]], in 1886 to honor the German biologist [[Albert Bernhard Frank]].<ref>{{Cite book|url=https://books.google.com/books?id=QQKdiHoNE_gC&q=A.B.Frank+frankia&pg=PA107|title=Prokaryotic Symbionts in Plants|last=Pawlowski|first=Katharina|date=2009-06-17|publisher=Springer Science & Business Media|isbn=9783540754602|pages=107}}</ref> Brunchorst considered the organism he had identified to be a filamentous fungus. {{ill|Jan-Hendrik Becking|lt=Becking|de||nl}} redefined the genus in 1970 as containing [[Prokaryote|prokaryotic]] [[Actinomycetota|actinomycetes]] and created the family [[Frankiaceae]] within the [[Actinomycetales]]. He retained the original name of ''Frankia'' for the genus.<ref>{{Cite web |url=http://web.uconn.edu/mcbstaff/benson/Frankia/FrankiaTaxonomy.htm |title=''Frankia'' taxonomy |access-date=2011-01-14 |archive-date=2011-07-27 |archive-url=https://web.archive.org/web/20110727030311/http://web.uconn.edu/mcbstaff/benson/Frankia/FrankiaTaxonomy.htm |url-status=dead }}</ref>

[[Image:A sectioned alder root nodule gall.JPG|right|202px|thumb|A section through an alder root nodule]]
__TOC__

==Overview==
Most ''Frankia'' [[Strain (biology)|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.<ref name=FAP>[https://frankia.mcb.uconn.edu Frankia and Actinorhizal Plants]</ref>

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 transfer|horizontal gene flow]] among the symbiotic prokaryotes.<ref name=FAP/>

''Frankia'' can resist low concentration of heavy metals such as, Cu, Co, and Zn.<ref>{{Cite journal|last1=Abdel‐lateif|first1=Khalid Salah El dein|last2=Mansour|first2=Samira R.|last3=El‐Badawy|first3=Mohamed F.|last4=Shohayeb|first4=Mohamed M.|date=2018|title=Isolation and molecular characterization of ''Frankia'' strains resistant to some heavy metals|journal=Journal of Basic Microbiology|volume=58|issue=9|pages=720–729|doi=10.1002/jobm.201800122|pmid=29962068|s2cid=49639716|issn=1521-4028}}</ref> ''Frankia'' may be an advantage for degraded soil. Degraded soil is known as soil that is heavy metal rich or nutrient depleted due to a drought. ''Frankia'' is a nitrogen-fixed organism, explaining why it is able to resist heavy metals.<ref>{{Cite journal|last1=El dein Abdel-lateif|first1=Khalid Salah|last2=Mansour|first2=Samira R.|last3=El-Badawy|first3=Mohamed F.|last4=Shohayeb|first4=Mohamed M.|date=September 2018|title=Isolation and molecular characterization of ''Frankia'' strains resistant to some heavy metals|journal=Journal of Basic Microbiology|volume=58|issue=9|pages=720–729|doi=10.1002/jobm.201800122|pmid=29962068|s2cid=49639716}}</ref>{{clarify|reason=Last two sentences incoherent.|date=May 2022}}

''Frankia'' is a [[Gram-positive bacteria|gram-positive Bacteria]] that is found on the roots of plants. The fact that ''Frankia'' is gram-positive means that the bacteria is made up of thick cell walls made out of protein called peptidologlycan. This helps with the resistance of the heavy metals that may be in the degraded soil.<ref>{{Cite journal|last1=Nouioui|first1=Imen|last2=Ghodhbane-Gtari|first2=Faten|last3=del Carmen Montero-Calasanz|first3=Maria|last4=Rohde|first4=Manfred|last5=Tisa|first5=Louis S.|last6=Gtari|first6=Maher|last7=Klenk|first7=Hans-Peter|date=2017-03-01|title=''Frankia inefficax'' sp. nov., an actinobacterial endophyte inducing ineffective, non nitrogen-fixing, root nodules on its actinorhizal host plants|journal=Antonie van Leeuwenhoek|volume=110|issue=3|pages=313–320|doi=10.1007/s10482-016-0801-7|pmid=27830471|s2cid=39458226|issn=1572-9699}}</ref>

''Frankia'' tolerates a narrow range of temperatures and soil pH levels. It grows best at around 30 degrees Celsius with an environment pH between 6.5 and 7.<ref>{{Cite journal|last1=Srivastava|first1=Amrita|last2=Singh|first2=Anumeha|last3=Singh|first3=Satya S.|last4=Mishra|first4=Arun K.|date=2017-04-16|title=Salt stress–induced changes in antioxidative defense system and proteome profiles of salt-tolerant and sensitive ''Frankia'' strains|journal=Journal of Environmental Science and Health, Part A|volume=52|issue=5|pages=420–428|doi=10.1080/10934529.2016.1270672|issn=1093-4529|pmid=28085556|s2cid=38519293}}</ref> These facts shows that ''Frankia'' is very sensitive to its environment. Though ''Frankia'' would not be suitable for all agriculture it does demonstrate possibilities in select areas, or in temperature controlled environments.{{citation needed|date=April 2023}}

==Symbiont plants==
{{Main|Actinorhizal plant}}
* All species in the genus ''[[Alder|Alnus]]'' in the family [[Betulaceae]]
* Some species in all four genera in the family [[Casuarinaceae]]
* Certain species in the genus ''[[Coriaria]]'' in the family [[Coriariaceae]]
* ''[[Datisca cannabina]]'' and ''[[Datisca glomerata]]'' in the family [[Datiscaceae]]
* All species in the three genera in the family [[Elaeagnaceae]], ''[[Elaeagnus]]'', ''[[Shepherdia]]'', and ''[[Hippophae]]''
* All species in the genera ''[[Myrica]]'', ''[[Morella (plant)|Morella]]'', and ''[[Comptonia (plant)|Comptonia]]'' in the family [[Myricaceae]].
* All species in six genera in the family [[Rhamnaceae]], ''[[Ceanothus]]'', ''[[Colletia]]'', ''[[Discaria]]'', ''[[Trevoa]]'', and possibly ''[[Adolphia]]''
* Some species in the family [[Rosaceae]] including all the species in the genera ''[[Cercocarpus]]'', ''[[Cowania (plant)|Cowania]]'', ''[[Purshia]]'', ''[[Chamaebatia]]'', and some species of ''[[Dryas (plant)|Dryas]]''<ref>{{cite book |last1=Schwintzer |first1=C. R. |last2=Tjepkema |first2=J. |title=The Biology of ''Frankia'' and Actinorhizal Plants |date=1990 |publisher=Academic Press |location=San Diego |isbn=978-0126332100}}</ref>

== Nodule Formation ==
[[File:Frankia Longitudinal Section Toluidine Blue- Atchison, Black.png|thumb|Longitudinal section of a ''Frankia'' nodule dyed with Toluidine Blue to highlight the vascular tissue in blue and purple.]]
''Frankia'' forms nodules via two methods of root infection, intercellularly and intracellularly.<ref name=":0">{{Cite journal |last=Santi |first=Carole |last2=Bogusz |first2=Didier |last3=Franche |first3=Claudine |date=2013-03-10 |title=Biological nitrogen fixation in non-legume plants |url=http://dx.doi.org/10.1093/aob/mct048 |journal=Annals of Botany |volume=111 |issue=5 |pages=743–767 |doi=10.1093/aob/mct048 |issn=1095-8290|pmc=3631332 }}</ref> [[Intracellular]] infection is characterized by initial root-hair deformation which is then infected by the filamentous ''Frankia''. The ''Frankia'' then moves within the root cells and forms a pre-nodule which is characterized by a bump on the root. This then gives rise to a Nodule primordium which feeds the bacteria via the vascular tissue of the plant allowing the nodule to mature.<ref name=":0" />

In contrast the intercellular infection does not have root hair deformation. Instead, the filamentous ''Frankia'' invades the roots in the space between cells on the root. After this invasion a Nodule primordium is created similarly to the intracellular mode of formation and the nodule matures.<ref name=":0" />

==Phylogeny==
The currently accepted taxonomy is based on the [[List of Prokaryotic names with Standing in Nomenclature]] (LPSN)<ref name=LPSN>{{cite web |author=A.C. Parte |url=https://lpsn.dsmz.de/genus/frankia |title=Frankia |access-date=2025-02-28 |publisher=[[List of Prokaryotic names with Standing in Nomenclature]] (LPSN) |display-authors=et al.}}</ref> and [[National Center for Biotechnology Information]] (NCBI).<ref name=NCBI>{{cite web |author=C.L. Schoch |url=https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=1854&lvl=3&lin=f&keep=1&srchmode=1&unlock |title=Frankia |access-date=2025-02-28 |publisher=[[National Center for Biotechnology Information]] (NCBI) taxonomy database |display-authors=et al.}}</ref>

{| class="wikitable"
|-
! colspan=1 style="width: 30em;" | 16S rRNA based [[The All-Species Living Tree Project|LTP]]_10_2024<ref>{{cite web |title=The LTP |url=https://imedea.uib-csic.es/mmg/ltp/#LTP| access-date=10 December 2024}}</ref><ref>{{cite web |title=LTP_all tree in newick format |url=https://imedea.uib-csic.es/mmg/ltp/wp-content/uploads/ltp/LTP_all_10_2024.ntree |access-date=10 December 2024}}</ref><ref>{{cite web |title=LTP_10_2024 Release Notes |url=https://imedea.uib-csic.es/mmg/ltp/wp-content/uploads/ltp/LTP_10_2024_release_notes.pdf |access-date=10 December 2024}}</ref>
! colspan=1 | 120 marker proteins based [[Genome Taxonomy Database|GTDB]] 09-RS220<ref name="about">{{cite web |title=GTDB release 09-RS220 |url=https://gtdb.ecogenomic.org/about#4%7C |website=[[Genome Taxonomy Database]] |access-date=10 May 2024}}</ref><ref name="tree">{{cite web |title=bac120_r220.sp_labels |url=https://data.gtdb.ecogenomic.org/releases/release220/220.0/auxillary_files/bac120_r220.sp_labels.tree |website=[[Genome Taxonomy Database]] |access-date=10 May 2024}}</ref><ref name="taxon_history">{{cite web |title=Taxon History |url=https://gtdb.ecogenomic.org/taxon_history/ |website=[[Genome Taxonomy Database]] |access-date=10 May 2024}}</ref>
|- 
| style="vertical-align:top|
{{barlabel |size=0 |at1=-6 |label1=''Protofrankia'' |bar1=green |at2=-2.5 |label2=''Frankia'' s.s. |bar2=green |at3=2 |label3=''Pseudofrankia'' |bar3=green |at4=5 |label4=''Parafrankia'' |bar4=green 
|cladogram=
{{Clade | style=font-size:90%;line-height:80%
|label1=''Frankia''
|1={{clade
  |1=''F. coriariae'' <small>Nouioui et al. 2017</small>|barbegin1=green|barenf1=green
  |2={{clade
    |1={{clade
      |1={{clade
        |1=''F. casuarinae'' <small>Nouioui et al. 2016</small>|barbegin1=green
        |2=''F. canadensis'' <small>Normand et al. 2018</small><ref>{{cite journal |author1=Normand, P  |author2=Nouioui, I |author3=Pujic, P |author4=Fournier, P |author5=Dubost, A |author6=Schwob, G |author7=Klenk, HP |author8=Nguyen, A |author9= Abrouk, D |author10=Herrera-Belaroussi, A |author11=Pothier, J.F. |author12=Pflüger, V |author13=Fernandez, M.P. |date=2018 |title= ''Frankia canadensis'' sp. nov., isolated from root nodules of ''Alnus incana'' subspecies ''rugosa'' |journal=Int J Syst Evol Microbiol |volume=68 |issue=9 |pages=3001–3011 |pmid=30059001 |doi= 10.1099/ijsem.0.002939| doi-access=free }}</ref>|bar2=green
         }}
      |2={{clade
        |1=''F. umida'' <small>Normand et al. 2023</small>|bar1=green
        |2={{clade
          |1=''[[Frankia alni|F. alni]]'' <small>(Woronin 1866) Von Tubeuf 1895</small>|bar1=green
          |2={{clade
            |1=''F. torreyi'' <small>Nouioui et al. 2019</small>|bar1=green
            |2={{clade
              |1="''F. gtarii''" <small>Nouioui et al. 2023</small>|bar1=green
              |2="''F. tisai''" <small>Nouioui et al. 2023</small>|barend2=green
               }}
             }}
           }}
         }}
       }}
    |2={{clade
      |1={{clade
        |1=''F. inefficax'' <small>Nouioui et al. 2017</small>|barbegin1=green
        |2={{clade
          |1=''F. asymbiotica'' <small>Nouioui et al. 2017</small>|bar1=green
          |2=''F. saprophytica'' <small>Nouioui et al. 2018</small>|barend2=green
           }}
         }}
      |2={{clade
        |1=''F. discariae'' <small>Nouioui et al. 2017</small>|barbegin1=green
        |2={{clade
          |1=''F. soli'' <small>Gtari et al. 2020</small>|bar1=green
          |2={{clade
            |1=''F. irregularis'' <small>Nouioui et al. 2018</small>|bar1=green
            |2={{clade
              |1=''F. colletiae'' <small>Nouioui et al. 2023</small>|bar1=green
              |2=''F. elaeagni'' <small>(Schroeter 1886) Becking <br/>1970 ex Nouioui et al. 2016</small>|barend2=green
               }}
             }}
           }}
         }}
       }}
     }}
   }}
}}
}}
|
{{Clade | style=font-size:90%;line-height:90%
|1={{clade
  |1={{clade
  |label1=''Protofrankia''
  |1={{clade
    |1="''Ca.'' Frankia meridionalis" <small>Nguyen et al. 2019</small>
    |2={{clade
      |1="''Ca.'' Frankia californiensis" <small>Normand et al. 2017</small><ref>{{cite journal |author1= Normand P|author2=Nguyen, T.V. |author3=Battenberg, K|author4=Berry, A.M. |author5=Heuvel, B.V. |author6=Fernandez, M.P. |author7=Pawlowski, K. |s2cid= 41316476 |date= 2017 |title=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 |journal =Int J Syst Evol Microbiol |volume=67 |issue=10 |pages=3706–3715 |pmid = 28884663 |doi=10.1099/ijsem.0.002147|doi-access=free }}</ref>
      |2=''P. coriariae'' [incl. "''Ca.'' P. datiscae" <small>([[Tomas Persson|Persson]] et al. 2011) Gtari 2022</small>]
       }}
     }}
     }}
  |2={{clade
    |1={{clade
    |label1=''Pseudofrankia''
    |1={{clade
      |1=''P. inefficax''
      |2={{clade
        |1=''P. asymbiotica''
        |2=''P. saprophytica''
         }}
       }}
       }}
    |2={{clade
      |label1=''Parafrankia''
      |1={{clade
        |1={{clade
          |1=''P. discariae''
          |2=''P. soli''
           }}
        |2={{clade
          |1=''P. irregularis''
          |2={{clade
            |1=''P. colletiae''
            |2=''P. elaeagni''
             }}
           }}
         }}
      |label2=''Frankia''
      |2={{clade
        |1=''F. casuarinae''
        |2={{clade
          |1={{clade
            |1=''F. canadensis''
            |2=''F. umida'' ["''Ca.'' F. nodulisporulans" <small>Herrera-Belaroussi et al. 2020</small>]
             }}
          |2={{clade
            |1={{clade
              |1=''[[Frankia alni|F. alni]]''
              |2=''F. torreyi''
               }}
            |2={{clade
              |1="''Ca.'' F. alpina" <small>Pozzi et al. 2020</small> [incl. "''F. subtilis''" <small>Brunchorst 1886</small>]
              |2={{clade
                |1="''F. gtarii''"
                |2="''F. tisai''"
                 }}
               }}
             }}
           }}
         }}
       }}
     }}
   }}
}}
|}
Species incertae sedis:
* ''F. nepalensis'' <small>Nouioui et al. 2023</small>

==See also==
* [[List of bacterial orders]]
* [[List of bacteria genera]]

==References==
{{Reflist|2}}

{{Portal bar|Biology}}
{{Bacteria classification}}
{{Taxonbar|from=Q134931}}
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[[Category:Actinomycetia]]
[[Category:Bacteria genera]]