Frankia Alni
| Frankia Alni | ||||||||||||
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Actinorrhiza root nodules of a black alder ( Alnus glutinosa ) with Frankia alni |
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| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Frankiaceae | ||||||||||||
| Becking 1970 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Frankia | ||||||||||||
| Brunchorst 1886 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Frankia Alni | ||||||||||||
| ( Voronin 1866) by Tubeuf 1895 |
Frankia alni is the only species of the genus Frankia , gram-positive , aerobic , filamentous (cell thread-forming) bacteria with a high GC content from the order of the Actinomycetales . The genus was named after the German microbiologist Albert Bernhard Frank (1839 to 1900). The bacteria belong to the nitrogen fixers and enter into a symbiosis with plants ( actinorrhiza ).
Symbiosis with plants
The soil-living bacteria occur both freely and in close symbiosis with woody plants. Representatives living in symbiosis can induce two different types of nodules on plant roots ( actinorrhiza ). The connection between root swelling and bacterial attack was first described in 1866 by the Russian botanist Mikhail Stepanowitsch Voronin together with the nodule bacteria of legumes.
The symbiosis with alder is relatively well studied . In contrast to fungi (which can also be symbionts of plants) Frankia has the ability to bind nitrogen from the air with the help of the enzyme complex nitrogenase and make it available to the plant. This allows the plant to thrive even in low-nitrogen soils. The high energy requirement for bacterial nitrogen fixation is covered by the plant in the form of carbohydrates from photosynthesis . The enrichment with nitrogen is so high that nitrogen-loving plants such as nettles ( Urtica sp.) Are often found as accompanying flora under alders .
The bacteria protect their oxygen-sensitive nitrogenase by enclosing them in spherical vesicles at the thickened ends of their cells. However, the transport of oxygen is a particular problem , since nitrogen fixation requires a great deal of energy and therefore also oxygen. To get enough oxygen at still low O 2 - partial pressure provide, is used by the plant leghemoglobin used. In contrast to other symbiotic nitrogen fixers (such as rhizobia ), Frankia can fix nitrogen without a symbiont and with full oxygen partial pressure .
In contrast to rhizobia, Frankia is less specialized in certain plant species as a symbiote. In addition to alder trees, the bacteria were also found on the roots of 8 other plant families ( actinorrhiza plants). In the past, these isolates were divided into several types. Today, however, only one species is assumed.
Synonyms for Frankia alni
Frankia alni is also known by the following species names:
- Frankia subtilis
- Nocardia alni
- Streptomyces alni
- Proactinomyces alni
- Actinomyces alni
- Plasmodiophora alni
- Schinzia alni
swell
- ↑ National Center for Biotechnology Information (NCBI) as of February 2007
literature
- Christa R. Schwintzer, John D. Tjepkema (Eds.): The Biology of Frankia and actinorhizal plants . Academic Press, San Diego CA et al. 1990, ISBN 0-12-633210-X .
- MS Voronin : About the swelling of the roots in the black alder (Alnus glutinosa) and common garden lupine (Lupinus mutabilis) . Académie, St. Petersburg 1866, ( Mémoires de l'Académie Impériale des Sciences de St. Pétersbourg , VII Series, vol. X, 6).
- Hans G. Schlegel: General microbiology . 7th revised edition. Thieme, Stuttgart 1992, ISBN 3-13-444607-3 , ( flexible paperback - bio ).
- Purves Biologie 9th edition page 1009 Spektrum Verlag *
Web links
- FrankiaHome (engl.)