Microbes iron-reducing

Anaerobic dissimilatory ferric iron-reducing microbes... 

Dissimilatory ferric iron reducing-microbes require a continued supply of ferric iron and other nutrients to degrade a significant volume of petroleum. Thus, the original emplacement of extensive ferric iron in a form accessible to microbes during early diagenesis of the Kuparuk... 

Iron(III)-reducing microbes can lead to increased mobility of many metals by reducing Fe oxides to which metals are bound. For example, Cummings et al. (1999) showed that Fe(III) reduction by the FeRB Shewanella alga mobilized arsenate [As(V)] that was bound to the iron oxides. Thus, seasonal cycles in... 

That something is iron. Iron can accept an electron, switching from a plus-three form to a plus-two form. Because electrons are the opposites of oxygens, if iron accepts an electron it can give a sulfite an oxygen, turning it back to sulfate. The sulfate bank is replenished—let them (the sulfate-reducing microbes) eat sulfate ... 

Microbiologically influenced corrosion is defined by the National Association of Corrosion Engineers as any form of corrosion that is influenced by the presence and/or activities of microorganisms. Although MIC appears to many humans to be a new phenomenon, it is not new to the microbes themselves. Microbial transformation of metals in their elemental and various mineral forms has been an essential part of material cycling on earth for billions of years. Some forms of metals such as reduced iron and manganese serve as energy sources for microbes, while oxidized forms of some metals can substitute for... 

To enhance iron excretion, intensive chelation therapy is used. The most successful drug is desferrioxamine B, a powerful Fe3+-chelator produced by the microbe Streptomyces pilosus,6 The formation constant for the Fe(III) complex, called ferrioxamine B, is 103afi. Used in conjunction with ascorbic acid—vitamin C, a reducing agent that reduces Fe3+ to the more soluble Fe2+— desferrioxamine clears several grams of iron per year from an overloaded patient. The ferrioxamine complex is excreted in the urine. 

Suzuki and Banfield (1999) discuss the similarities between the uranium-microbe interactions and transuranic-microbe interactions. Macaskie (1991) notes that it is possible to extrapolate the data for microbial uranium accumulation to other actinides. Hodge et al. (1973) observe that the biological behavior of uranium, thorium, and plutonium resemble that of ferric iron. Microbes can also affect the speciation and transport of multivalent fission products. For example, Fe " -reducing bacteria and sulfate-reducing bacteria can reduce soluble pertechnetate to insoluble Tc(IV), as discussed by Lloyd et al. (1997). For additional information about these topics, the reader is referred to the references cites above. Applications of these principles are described in the section on bioremediation later in this chapter. 

As summarized by Jacobson (1994), biological Fe(III) reduction will be more important than chemical reduction when amorphous Fe(IIl) oxides are plentiful and continually regenerated, or H2S production is low relative to the Fe(III) concentration. This first condition is likely to be met in the rhizosphere where radial O2 loss drives Fe oxide formation. The second condition will be met in low-salinity wetlands, or in saline systems with mineral (i.e., iron-rich) sediments. However, even chemical reduction of Fe(III) is ultimately due to microbes since the H2S that reduces the Fe is the result of a biological process, SO4" reduction (Megonigal et al., 2004). 

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