Frankia alni
A Microbial Biorealm page on the genus Frankia alni
Classification
Higher order taxa
cellular organisms; Bacteria; Actinobacteria; Actinobacteria (class); Actinobacteridae; Actinomycetales; Frankineae; Frankiaceae; Frankia
Species
NCBI: Taxonomy |
Frankia alni
Description and significance
Species of the Frankia Genus are Gram positive bacteria.Frankia sp. are filamentous nitrogen-fixing bacterium that grow by branching and tip extension and thus resemble the antibiotic-producing Streptomyces sp. . They live in the soil and have a symbiotic relationship with certain woody angiosperms, called actinorhizal plants. During growth, the Frankia sp. produce three cell types: sporangiospores, hyphae, and diazo-vesicles (spherical, thick walled, lipid-enveloped cellular structures). The diazo-vesicles are responsible for the supplying of sufficient Nitrogen to the host plant during symbiosis. Frankia supplies most or all of the host plant nitrogen needs without added nitrogen and thus can establish a nitrogen-fixing symbiosis with host plants where nitrogen is the limiting factor in the growth of the host. Therefore, actinorhizal plants colonize and often prosper in soils that are low in combined nitrogen. Symbiosis of this kind adds a large proportion of new nitrogen to several ecosystems such as temperate forests, dry chaparral, sand dunes, mine wastes, & etc.
The Frankia alni ACN14a was first isolated in Tadoussac, Canada from a green alder (Alnus crispa). Except for Australia and Antarctica, Frankia alni can be isolated from soils on all continents. Frankia alni causes root hair deformation in a way that it enters the cortical cells and induces the nodule formations, which look like those induced by Rhizobium in legumes. Then, the nodules are colonized by vegetative hyphae (mycelium filaments) that differentiate into diazo-vesicles. Reductive nitrogen fixation takes place in the diazo-vesicles and this process is protected from molecular oxygen by many layers of tightly stacked hopanoid lipids.
Genome structure
The genome sequencing project of Frankia alni ACN14a was done at the Genoscope sequencing center and was completed on 03/08/2006. The genome of Frankia alni ACN14a contains a circular chromosome that is 7,497,934 necleotides long. It also cantains plasmids, but the amount was not clear based on my research. It has a high G-C content of 72.8% and contains 88% coding regions. The genome has 6,786 genes, comprising of 6,711 protein coding genes, 63 structural RNAs, and 12 pseudo genes.
Cell structure and metabolism
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Ecology
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Pathology
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Application to Biotechnology
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Current Research
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References
Edited by student of Rachel Larsen and Kit Pogliano