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Principle
- This medium is used for the isolation of iron bacteria like Sphaerotilus-Leptothrix group. Sphaerotilus-Leptothrix is filamentous bacteria, forms sheath deposited with ferric hydroxide and manganese dioxide.
- The specific deposition of ferric ions on the sheath of S. discophorus was demonstrated by Rogers and Anderson (1976). Iron bacteria obtain energy by the oxidation of iron from the ferrous to the ferric state.
- Some bacteria that do not oxidize ferrous ions may dissolve or deposit them indirectly. During their growth, they either liberate iron by consuming organic radicals to which the iron is attached or adjust environmental conditions to permit the deposition of iron.
- Isolation Medium for Iron Bacteria is recommended by APHA (1976) for the isolation of iron bacteria, especially those belonging to the Sphaerotilus-Leptothrix group. The medium is composed of Dextrose, ammonium sulphate, calcium nitrate, dipotassium hydrogen phosphate, magnesium sulphate, potassium chloride, calcium carbonate, cyanocobalamin, thiamine and agar.
- Dextrose is the source of carbon. Magnesium sulphate, ammonium sulphate, potassium chloride and calcium nitrate are sources of ions that stimulate metabolism. Dipotassium phosphate buffers the medium. The bacteria of both genera, Sphaerotilus and Leptothrix require Cyanocobalamin as an essential growth factor. While some Leptothrix strains require additional thiamine as a growth factor.
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