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Iron-oxidizing bacteria
Iron-oxidizing bacteria (or iron bacteria) are chemotrophic bacteria that derive energy by oxidizing dissolved 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 the oxidation.
When de-oxygenated water reaches a source of oxygen, iron bacteria convert dissolved iron into an insoluble reddish-brown gelatinous slime that discolors stream beds and can stain plumbing fixtures, clothing, or utensils washed with the water carrying it.
Organic material dissolved in water is often the underlying cause of an iron-oxidizing bacteria population. Groundwater may be naturally de-oxygenated by decaying vegetation in swamps. Useful mineral deposits of bog iron ore have formed where groundwater has historically emerged and been exposed to atmospheric oxygen. Anthropogenic hazards like landfill leachate, septic drain fields, or leakage of light petroleum fuels like gasoline are other possible sources of organic materials allowing soil microbes to de-oxygenate groundwater.
A similar reaction may form black deposits of manganese dioxide from dissolved manganese but is less common because of the relative abundance of iron (5.4%) in comparison to manganese (0.1%) in average soils. The sulfurous smell of rot or decay sometimes associated with iron-oxidizing bacteria results from the enzymatic conversion of soil sulfates to volatile hydrogen sulfide as an alternative source of oxygen in anaerobic water.
Iron is a very important chemical element required by living organisms to carry out numerous metabolic reactions such as the formation of proteins involved in biochemical reactions. Examples of these proteins include iron–sulfur proteins, hemoglobin, and coordination complexes. Iron has a widespread distribution globally and is considered one of the most abundant elements in the Earth's crust, soil, and sediments. Iron is a trace element in marine environments. Its role as the electron donor of some chemolithotrophs is probably very ancient.
The anoxygenic phototrophic iron oxidation was the first anaerobic metabolism to be described within the iron anaerobic oxidation metabolism. The photoferrotrophic bacteria use Fe2+ as electron donor and the energy from light to assimilate CO2 into biomass through the Calvin Benson-Bassam cycle (or rTCA cycle) in a neutrophilic environment (pH 5.5-7.2), producing Fe3+ oxides as a waste product that precipitates as a mineral, according to the following stoichiometry (4 mM of Fe(II) can yield 1 mM of CH2O):
HCO−3 + 4Fe(II) + 10H2O → [CH2O] + 4Fe(OH)3 + 7H+ (∆G° > 0)
Nevertheless, some bacteria do not use the photoautotrophic Fe(II) oxidation metabolism for growth purposes. Instead, it has been suggested that these groups are sensitive to Fe(II) and therefore oxidize Fe(II) into more insoluble Fe(III) oxide to reduce its toxicity, enabling them to grow in the presence of Fe(II). On the other hand, based on experiments with Rhodobacter capsulatus SB1003 (photoheterotrophic), it has been demonstrated that the oxidation of Fe(II) might be the mechanisms whereby the bacteria are enabled to access organic carbon sources (acetate, succinate) whose use depends on Fe(II) oxidation. Nonetheless, many iron-oxidizing bacteria can use other compounds as electron donors in addition to Fe(II), or even perform dissimilatory Fe(III) reduction as the Geobacter metallireducens.
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Iron-oxidizing bacteria AI simulator
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Iron-oxidizing bacteria
Iron-oxidizing bacteria (or iron bacteria) are chemotrophic bacteria that derive energy by oxidizing dissolved 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 the oxidation.
When de-oxygenated water reaches a source of oxygen, iron bacteria convert dissolved iron into an insoluble reddish-brown gelatinous slime that discolors stream beds and can stain plumbing fixtures, clothing, or utensils washed with the water carrying it.
Organic material dissolved in water is often the underlying cause of an iron-oxidizing bacteria population. Groundwater may be naturally de-oxygenated by decaying vegetation in swamps. Useful mineral deposits of bog iron ore have formed where groundwater has historically emerged and been exposed to atmospheric oxygen. Anthropogenic hazards like landfill leachate, septic drain fields, or leakage of light petroleum fuels like gasoline are other possible sources of organic materials allowing soil microbes to de-oxygenate groundwater.
A similar reaction may form black deposits of manganese dioxide from dissolved manganese but is less common because of the relative abundance of iron (5.4%) in comparison to manganese (0.1%) in average soils. The sulfurous smell of rot or decay sometimes associated with iron-oxidizing bacteria results from the enzymatic conversion of soil sulfates to volatile hydrogen sulfide as an alternative source of oxygen in anaerobic water.
Iron is a very important chemical element required by living organisms to carry out numerous metabolic reactions such as the formation of proteins involved in biochemical reactions. Examples of these proteins include iron–sulfur proteins, hemoglobin, and coordination complexes. Iron has a widespread distribution globally and is considered one of the most abundant elements in the Earth's crust, soil, and sediments. Iron is a trace element in marine environments. Its role as the electron donor of some chemolithotrophs is probably very ancient.
The anoxygenic phototrophic iron oxidation was the first anaerobic metabolism to be described within the iron anaerobic oxidation metabolism. The photoferrotrophic bacteria use Fe2+ as electron donor and the energy from light to assimilate CO2 into biomass through the Calvin Benson-Bassam cycle (or rTCA cycle) in a neutrophilic environment (pH 5.5-7.2), producing Fe3+ oxides as a waste product that precipitates as a mineral, according to the following stoichiometry (4 mM of Fe(II) can yield 1 mM of CH2O):
HCO−3 + 4Fe(II) + 10H2O → [CH2O] + 4Fe(OH)3 + 7H+ (∆G° > 0)
Nevertheless, some bacteria do not use the photoautotrophic Fe(II) oxidation metabolism for growth purposes. Instead, it has been suggested that these groups are sensitive to Fe(II) and therefore oxidize Fe(II) into more insoluble Fe(III) oxide to reduce its toxicity, enabling them to grow in the presence of Fe(II). On the other hand, based on experiments with Rhodobacter capsulatus SB1003 (photoheterotrophic), it has been demonstrated that the oxidation of Fe(II) might be the mechanisms whereby the bacteria are enabled to access organic carbon sources (acetate, succinate) whose use depends on Fe(II) oxidation. Nonetheless, many iron-oxidizing bacteria can use other compounds as electron donors in addition to Fe(II), or even perform dissimilatory Fe(III) reduction as the Geobacter metallireducens.