Frankia alni
Frankia alni
Frankia alni is the only species of the genus Frankia, gram-positive, aerobic, filamentous ( hyphae -forming ) bacteria with high GC content of the order Actinomycetales. The genus was named after the German microbiologist Albert Bernhard Frank ( 1839-1900 ). The bacteria belong to the diazotrophs and go into a symbiosis with plants ( Aktinorrhiza ).
Symbiosis with plants
The ground-dwelling bacteria are both free and in close symbiosis ago with woody plants. Symbiotic living representative of two different types of nodules on plant roots induce ( Aktinorrhiza ). The relationship between root vigor and swelling attack by bacteria was first described in 1866 by the Russian botanist Mikhail Stepanovich Voronin, along with the root nodule bacteria of leguminous plants.
Relatively well studied is the symbiosis with alder. In contrast to fungi ( which may also be symbionts of plants ) Frankia has the ability to help with the enzyme complex nitrogenase to fix nitrogen from the air and make it available to the plant. This allows the plant to thrive in nitrogen-poor soils. The high energy required for bacterial nitrogen fixation is covered by the plant in the form of carbohydrates from photosynthesis. The enrichment with nitrogen is so high that under alder often nitrogen- loving plants such as nettles (Urtica sp.) Encounters as accompanying flora.
Your oxygen-sensitive nitrogenase protect the bacteria by them include the thickened ends of their cells into spherical vesicles. A particular problem but now forms the transport of oxygen, because nitrogen fixation lot of energy and therefore always needs oxygen. In order to provide enough oxygen at still low O2 partial pressure, is used by the plant leghemoglobin. Unlike other symbiotic diazotrophs ( eg rhizobia ) can fix nitrogen Frankia therefore without symbiont and at full oxygen partial pressure.
In contrast to rhizobia Frankia is less specialized in certain plant species as a symbiont. Thus, the bacteria ( Aktinorrhiza plants) were found next to alder also on roots of 8 different plant families. Previously divided these isolates you in several ways. Today one only assumes, however of some sort.
Synonyms for Frankia alni
Frankia alni is also known under the following names of species:
- Frankia subtilis
- Nocardia alni
- Streptomyces alni
- Proactinomyces alni
- Actinomyces alni
- Plasmodiophora alni
- Schinzia alni