Iron-oxidising bacteria

Brock, T.D. and Gustafson, J., 1976. Ferric iron reduction by sulfur- and iron-oxidising bacteria. Appl. Environ. Microbiol., 32 567—571. 

Fe-Mn oxides/hydroxides Filamentous, putative microbial textures, often with morphologies resembling iron-oxidising bacteria, are extremely common in Fe-Mn-Si oxyhydroxides from a variety of mid-ocean ridges (e.g. Juniper Fouquet, 1988 Bogdanov etal., 1997 Fortin etal., 1998 Boyd Scott, 1999 Halbach etal., 2001 Kennedy etal., in press Leveille Juniper, 2002), seamounts (Alt, 1988 Bogdanov etal., 1997 Boyd Scott, 1999 Boyd ... 

Steel surfaces can develop biofilms that may form chemical concentration or differential aeration cells resulting in localised corrosion. In addition, if chloride ions are present, the pH of the electrolyte under tubercles (discrete hemispherical mounds [30]) may further decrease, enhancing localised corrosion. In the presence of certain bacteria such as iron-oxidising bacteria (lOB) [32], the chemical conditions under the tubercles formed by the bacteria may become very acidic as d ions combine with the ferric ions produced by lOB to form a very corrosive acidic ferric chloride solution inside the tubercle [30]. 

Reduction of the pitting potential because of (1) the crevice-like action of surface deposits produced by iron-oxidising bacteria, or (2) the activating effect of sulphide or thiosulphate produced by SRB, or (3) simply the effect of silicate in the water. 

Although in this report the type of the bacteria (lOB or IRB) was not specified, from general recognition of iron bacteria (see [38]), it may be anticipated that it was iron-oxidising bacteria whose number had been adversely affected by applying voltage. 

Chamritski et al. [73] found that MIC of stainless steel 304 in low-chloride (less than l(X)ppm) waters could be caused by bacteria such as iron-oxidising... 

A good way to estimate total number of bacteria by using staining/counting techniques It can be used for direct inspection of certain large, distinctively shaped microorganisms (such as filamentous iron bacteria and stalked iron oxidisers such as Gal-lionella)... 

Iron is essential for life and is required for many different types of iron-containing proteins. Microbes and other organisms go to extraordinary lengths to acquire Fe. Many microbes secrete specific and high affinity Fe chelators known as siderophores. More than 200 are known in bacteria alone (Neilands 1981). Siderophores overcome the problem of the low solubility of Felll especially in oxidising environments, and... 

Iron is apt to be troublesome when present in quantities of 1 part per 100,000 and upwards. The metal oxidises, and hydrated oxide (rust) precipitates out on standing this may block the pipes conveying the water. This oxidation is assisted by certain lowly organisms known as iron bacteria.1 Iron salts are not toxic, but have a certain medicinal value and impart a bitter taste to the water. Copper salts are frequently employed to remove algae, 0-3 parts per 100,000 being about the minimum effective concentration of copper sulphate for this purpose. At such dilutions the salt is not prejudicial to the human organism. 

Mumford Proa. Ghent. Soc., 1913, 103, 645) describes an organism through the agency of which a dilute solution of ferrous ammonium sulphate was completely oxidised to feme hydroxide m thirty-six hours at 37° 0, no iron remaining in solution. See also Ellis, Iron Bacteria (Methuen, 1920). 

Iron is stored in these proteins in the ferric form, but is taken up as Fe +, which is oxidised by ferroxidase sites (a more detailed account of iron incorporation into ferritins is given in Chapter 19). As we point out in Chapter 13, ferritins are members of the much larger di-iron protein family. After oxidation, the Fe migrates to the interior cavity of the protein to form an amorphous ferric phosphate core. Whereas the ferritins in bacteria appear to fulfil the classical role of iron storage proteins, the physiological role of bacterioferritins is less clear. In Escherichia coli, it seems unlikely that bacterioferritin plays a major role in iron storage. 

Croal, L.R., Johnson, C.M., Beard, B.L., and Newman, D.K., 2004. Iron isotope fractionation by Fe(II(-oxidising photoautotrophic bacteria. Geochim. Cosmochim. Acta, 68, 1227-42. 

The aqueous chemistry of iron is also important in a number of other settings. Iron can be the dominant cation released in acid rock drainage, due to the oxidation of pyrite (FeS2(s)) when it becomes exposed to air and water. This process is catalysed by bacteria which cycle ferrous iron back to ferric iron which, in turn, can oxidise further pyrite. Thus, the rate of oxidation will depend on the aqueous concentration of ferric iron. If insufficient iron (and acid) is produced or the iron is removed by the inherent neutralisation capacity of the material, the rate of oxidation will be substantially reduced. The precipitation of iron oxyhydroxide phases and their ability to adsorb other aqueous elements have also been studied in detail (Dzombak and Morel, 1990). The removal of arsenic from drinking water by hydrous iron oxides is one example of these adsorption reactions. 

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