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Table 1 Free-living and symbiotic nitrogen fixing bacteria

From: Nitrogen fixation in eukaryotes – New models for symbiosis

  Division Selected species Selected symbiotic members Eucaryotic hosts Localisation within host References
archeae Methanosarcinales Methanosarcina sp. n.d. n.d. --- [18]
  Methanobacteriales Methanothermobacter sp. n.d. n.d. --- [19,20]
   Methanobacterium sp.     
bacteria Cyanobacteria Nostoc sp. Nostoc sp. Bryophytes (e.g. hornworts) extracellular (within cavities of the gametophyte) [79]
   Anabaena sp. Anabaena sp. Pteridophytes (Azolla) extracellular (within cavities of the dorsal leaves) [80,85,88]
   Trichodesmium sp. Cyanothece sp. Gymnosperms (cycads) extracellular (within coralloid roots) [81]
   Synechococcus sp.   Angiosperms (Gunnera) intracellular (within cells of the stem gland) [87]
   Cyanothece sp.   Fungi (cyanolichens) extracellular (in cephalodia or in the thallus) [50,51]
     Diatoms (R. gibba) intracellular [97,102]
     Sponges (Dysidea spp.) extracellular [30,31]
  Actinobacteria Frankia sp. Frankia sp. Actinorhizal plants root-nodules [57]
  Proteobacteria α: Sinorhizobium sp., Mesorhizobium sp. Bradyrhizobium sp. Legumes intracellular (in root-nodules) [63,64,68]
   β: Azoarcus sp., Burkholderia sp. Rhizobium sp. Legumes intracellular (in root-nodules)  
   γ: Azotobacter sp., Pseudomonas sp. Sinorhizobium sp. Legumes intracellular (in root-nodules)  
   Klebsiella pneumoniae, Erwinia sp. Azorhizobium sp. Legumes intracellular (in root-nodules)  
   δ: Gloeobacter sp., Desulfovibrio sp. Burkholderia sp. AM fungi intracellular [54]
    Azospirillum sp. Grasses/nonleguminous crops extracellular (w/o nodulation) [76]
    Azoarcus sp. Grasses/nonleguminous crops inter- and intracellular (w/o nodulation) [77]
    Klebsiella pneumoniae nonleguminous crops extracellular [107]
  Firmicutes (Clostridia) Clostridium sp. n.d. n.d. --- [108]
  Bacteroidetes/Chlorobiales Chlorobium sp. n.d. n.d. --- [109]
  Spirochaetales Treponema sp. Treponema ZAS-9 Termites extracellular (in the hindgut) [43]
  Chloroflexi Dehalococcoides sp. n.d. n.d. --- [110]
  1. Overview of nitrogen fixing bacteria, including selected symbiotic interactions, possible host organisms and symbiont localisation. Details of the individual symbiotic associations are described in the text. n.d.: not detected