Question

Leptotbrix is an example of iron bacteria. Which of the following statements best fit the iron bacteria?

• A. They oxidise ferrous compounds to ferric oxide
• B. They are responsible for preservation of iron-rich artefacts archaeological material
• C. They cause rusting of iron
• D. They cause iron to be deposited In the livers of animals

Answer 1

Answer: (A)

They oxidise ferrous compounds to ferric oxide

Iron-oxidizing bacteria are chemotrophic bacteria that derive the energy they need to live and multiply by oxidizing dissolved ferrous iron. They are known to grow and proliferate in waters containing iron concentrations as low as 0.1 mg/L. However, at least 0.3 ppm of dissolved oxygen is needed to carry out oxidation. Iron-oxidizing bacteria colonize the transition zone where de-oxygenated water from an anaerobic environment flows into an aerobic environment. Groundwater containing dissolved organic material may be de-oxygenated by microorganisms feeding on that dissolved organic material. Where concentrations of organic material exceed the concentration of dissolved oxygen required for complete oxidation, microbial populations that contain iron-reducing bacteria can reduce insoluble ferric oxide in aquifer soils to soluble ferrous hydroxide and use the oxygen released by that change to oxidize some of the remaining organic material. When the de-oxygenated water reaches a source of oxygen, iron-oxidizing bacteria use that oxygen to convert the soluble ferrous iron back into an insoluble reddish precipitate of ferric iron.

So the correct option is 'they oxidise ferrous compounds to ferric oxide'.