Characterization of extracellular minerals produced during dissimilatory Fe(III) and U(VI) reduction at 100 °C by Pyrobaculum islandicum

Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.
Geobiology (Impact Factor: 3.83). 04/2008; 6(2):147-54. DOI: 10.1111/j.1472-4669.2007.00142.x
Source: PubMed


In order to gain insight into the significance of biotic metal reduction and mineral formation in hyperthermophilic environments, metal mineralization as a result of the dissimilatory reduction of poorly crystalline Fe(III) oxide, and U(VI) reduction at 100 degrees C by Pyrobaculum islandicum was investigated. When P. islandicum was grown in a medium with poorly crystalline Fe(III) oxide as an electron acceptor and hydrogen as an electron donor, the Fe(III) oxide was reduced to an extracellular, ultrafine-grained magnetite with characteristics similar to that found in some hot environments and that was previously thought to be of abiotic origin. Furthermore, cell suspensions of P. islandicum rapidly reduced the soluble and oxidized form of uranium, U(VI), to extracellular precipitates of the highly insoluble U(IV) mineral, uraninite (UO(2)). The reduction of U(VI) was dependent on the presence of hydrogen as the electron donor. These findings suggest that microbes may play a key role in metal deposition in hyperthermophilic environments and provide a plausible explanation for such phenomena as magnetite accumulation and formation of uranium deposits at ca. 100 degrees C.

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    • "Since the first discovery of Fe 3+ reduction by thermophilic enrichment cultures (Slobodkin et al., 1995), many studies have shown that thermophilic bacteria and archaea are capable of growing organotrophically with fermentable substrates or chemolithoautotrophically with molecular hydrogen when coupled with reduction of Fe 3+ to Fe 2+ (Slobodkin et al., 1997; Vargas et al., 1998; Zavarzina et al., 2007; Kashefi et al., 2002; Gavrilov et al., 2003). Furthermore , various thermophilic and hyperthermophilic archaea and bacteria have been reported to possess the ability to reduce structural Fe 3+ in ferruginous smectite with H 2 as an electron donor (Kashefi et al., 2008). The results of these studies suggest the possibility of reduction of toxic metal ions by biogenic Fe 2+ in clay minerals as an electron donor (Jaisi et al., 2009; Bishop et al., 2012; Zhang et al., 2012; Bishop et al., 2014). "
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