Bacteria iron-reducing

There are other micro-organisms in addition to SRB which are also important in corrosion. For example, the MIC of stainless steel 304 in low-chloride natural water can involve the combination of some or all of the following factors [73]  

The reducing effects of IRB on metals such as copper, nickel, gold and silver have been known for nearly 50 years [ 111]. As the name implies, IRB act by reduction of the generally insoluble Fe compounds to the soluble Fe , exposing the metal beneath a ferric oxide protective layer to the corrosive environment [31,58,64]. 

It is important to understand how iron-reducing bacteria can reduce iron, or more precisely, ferric iron ion. The reason is that while the bacteria can reduce iron in some way or another, it is one of these methods that may be of more importance with regard to its contribution to corrosion. In the following section, possible reasons and mechanisms for microbial iron reduction are discussed. 

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Ganesh R, KG Robinson, GD Feed, GS Sayler (1997) Reduction of hexavalent uranium from organic complexes by sulfate- and iron-reducing bacteria. Appl Environ Microbiol 63 4385-4391. 

Respiration, as we have described, drives two half-reactions, one to donate electrons and one to accept them. Iron-reducing bacteria, for example, can live on acetate, which is produced during the breakdown of organic matter. Oxidizing acetate provides electrons,... 

Iron-reducing bacteria from a copper-contaminated sediment were more tolerant of copper adsorbed to hydrous ferric oxide (HFO) than were pristine-sediment bacteria (Markwiese et al. 1998). Copper-tolerant bacteria were more efficient in reducing contaminated HFO, with greater potential for copper mobilization in aquatic sediments (Markwiese et al. 1998). 

Markwiese, J.T., J.S. Meyer, and PJ.S. Colberg. 1998. Copper tolerance in iron-reducing bacteria implications for copper mobilization in sediments. Environ. Toxicol. Chem. 17 675-678. 

Straub, K. L., Hanzlik, M. and Buchholz-Cleven, B. E. E. (1998). The use of biologically produced ferrihydrite for the isolation of novel iron-reducing bacteria, Syst. Appl. Microbiol., 21, 442-449. 

Zhang C, Liu S, Phelps TJ, Cole DR, Horita J, Fortier SM, Elless M, Valley JW (1997) Physiochemical, mineralogical, and isotopic characterization of magnetite-rich iron oxides formed by thermophilic iron-reducing bacteria. Geochim Cosmochim Acta 61 4621-4632... 

Parmar N, Warren LA, Roden EE, Eerris EG (2000) Solid phase capture of strontium by the iron reducing bacteria Shewanella alga strain BrY. Chem Geol 169 281-288 Pearson MJ (1974) Sideritic concretions from the Westphalian of Yorkshire a chemical investigation of the carbonate phase. Min Mag 39 696-699... 

Achtnich C, Schuhmann A, Wind T, Conrad R. 1995. Role of interspecies H2 transfer to sulfate and ferric iron-reducing bacteria in acetate consumption in anoxic paddy soil. FEMS Microbiology Ecology 16 61-69. 

Wiehnga B, Mizuba MM, Fendorf S. 2001. Iron promoted reduction of chromate by dis-similatory iron-reducing bacteria. Environmental Science and Technology 35 522-521. 

Biooxidation hy aerobic or microaerophilic bacteria binding with ferrous ions produced by iron-reducing bacteria biooxidation by phototrophic bacteria... 

This requires a biomass which can be metabolized. The process usually involves enzymatic transfer of electrons by micro-organisms from the decomposing biomass (represented in the above equation as CH2O) to the Fe " in Fe " oxides. As seen from eq.16.3, reduction consumes protons and is, therefore, favoured, the lower the pH (see also Chap. 12). It usually takes place when all pores are filled with water (see reviews by Fischer, 1988 and Van Breemen, 1988). Biotic reduction of Fe oxides is now recognized as an important process in the oxidation (metabolism) of organic pollutants in soils by dissimilatory, iron-reducing bacteria. 

F. (2000) Dissimilatory iron-reducing bacteria can influence the reduction of carbon tetrachloride by iron metal. Environ. Sd. Techn. 34 2461-2464... 

UVi reduced to U,v by iron-reducing bacteria. May be important in the bio-geochemical deposit of U ... 

Iron-reducing bacteria might be of use in decontaminating (precipitating) uranium-. polluted water.. ... 

Reduction of nitro aromatic compounds often appears to be a two-step process, in which a mediator is required for facile transfer of electrons from a bulk reductant to the contaminant. A well documented example is the coupling of organic matter oxidation by iron reducing bacteria to "abiotic" nitro reduction by biogenic Fe(II) that is adsorbed to mineral surfaces in a column containing aquifer material (36, 39, 76). 

Like the various forms of iron, NOM apparently serves as both bulk reductant and mediator of reduction as well as bulk reductant (recall section 2.2.2). NOM also can act as an electron acceptor for microbial respiration by iron reducing bacteria (26), thereby facilitating the catabolism of aromatic hydrocarbons under anaerobic conditions (103). In general, it appears that NOM can mediate electron transfer between a wide range of donors and acceptors in environmental systems (104,105). In this way, NOM probably facilitates many redox reactions that are favorable in a thermodynamic sense but do not occur by direct interaction between donor and acceptor due to unfavorable kinetics. 

DOM can also act as an electron acceptor for biotically mediated oxidation reactions. Many active microorganisms, particularly phototrophs, produce reductants in excess of metabolic needs that must be regenerated by transfering electrons to acceptors in the environment via membrane-spanning reductases (Price and Morel, 1990). It has been discovered that some iron-reducing bacteria use humic and fulvic acids as terminal electron acceptors for their respiratory transport systems (Coates et al., 1998). 

UVife reduced to U by iron- Iron-reducing bacteria nu t. rediK bactetia.M be beofuse indecootaoilnat-... 

Eredrickson J. K. and Gorby Y. A. (1996) Environmental processes mediated by iron-reducing bacteria. Curr. Opin. Biotech. 7, 287 -294. 

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