Table 1

Free-living and symbiotic nitrogen fixing bacteria


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]

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

Kneip et al. BMC Evolutionary Biology 2007 7:55   doi:10.1186/1471-2148-7-55