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Principle
- Plants mainly acquire iron from the rhizosphere. Though Fe is one of the most abundant metals in the earth's crust, its availability to plant roots is very low. Iron availability is dictated by the soil redox potential and pH.
- In soils that are aerobic or of higher pH, iron is readily oxidized, and is predominately in the form of insoluble ferric oxides. At lower pH, the ferric Fe is free from the oxide and becomes more available for uptake by roots. Plants use two strategies to acquire iron.
- The strategy I involve acidification of the rhizosphere followed by reduction of Fe3+ ions by membrane-bound Fe (III)-chelate reductase and subsequent uptake of Fe2+ into root cells. Anaerobic ammonium oxidation coupled to iron (III) reduction (termed Feammox) is a recently discovered pathway of nitrogen cycling. Some iron-reducing bacteria like Anaeromyxobacter, Pseudomonas and Geobacter bacteria play an essential role in the Feammox process.
- In this process, the iron-reducing bacteria convert Fe3+ to Fe2+, which is easily available by the plants, coupled with the conversion of ammonia to free nitrogen and nitrates. Enrichment broth for iron bacteria is used for the cultivation of iron-oxidizing bacteria.
- The media is composed of ferrous sulfate, ammonium sulfate, calcium nitrate, dipotassium phosphate, magnesium sulfate and potassium chloride. The media contains all the essential ions, that support the growth of iron-reducing and oxidizing bacteria. Media is generally used for the cultivation of agriculturally important microorganisms like Thiobacillus ferrooxidans.
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