Microbial reduction of Fe(III) in the Fithian and Muloorina illites; contrasting extents and rates of bioreduction

• Published in: Clays and clay minerals Vol. 54; no. 1; pp. 67 - 79
• Main Authors: Seabaugh, Jennifer L, Dong, Hailiang, Eberl, Dennis D, Morton, John P, Kim, Jinwook
• Format: Journal Article
• Language: English
• Published: Boulder, CO Clay Minerals Society 01.02.2006; The Clay Minerals Society
• Subjects: bioreduction; buffers; chemical properties; clay mineralogy; Cn32; Earth sciences; Earth, ocean, space; Exact sciences and technology; experimental studies; ferric iron; ferrous iron; Fithian; Fithian Illite; geochemistry; goethite; Illite; iron; jarosite; metals; Microbial Fe(iii) Reduction; microorganisms; Mineralogy; Mossbauer spectra; Mossbauer Spectroscopy; Muloorina; Muloorina Illite; oxides; rates; reduction; rock, sediment, soil; sed rocks, sediments; Sedimentary petrology; sheet silicates; Shewanella Putrefaciens; Silicates; spectra; sulfates; experimental studies; illite; minerals; Mössbauer Spectroscopy; oxides; bacteria; ferric iron; X-ray diffraction; TEM data; sulfates; goethite; CN32; Mossbauer spectroscopy; pH; sheet silicates; silicates; transmission electron microscopy; soils; suspension; hoelite; buffers; dissolution; jarosite; aqueous solutions; Shewanella putrefaciens; organic minerals; Fithian; Microbial Fe(III) Reduction; hydroxides; prokaryotes; chemical reduction; Muloorina; clay minerals; biogenic effects
• ISSN: 0009-8604; 1552-8367
• DOI: 10.1346/CCMN.2006.0540109

Shewanella putrefaciens CN32 reduces Fe(III) within two illites which have different properties: the Fithian bulk fraction and the <0.2 µm fraction of Muloorina. The Fithian illite contained 4.6% (w/w) total Fe, 81% of which was Fe(III). It was dominated by illite with some jarosite (approximately 32% of the total Fe(III)) and goethite (11% of the total Fe(III)). The Muloorina illite was pure and contained 9.2% Fe, 93% of which was Fe(III). Illite suspensions were buffered at pH 7 and were inoculated with CN32 cells with lactate as the electron donor. Select treatments included anthraquinone-2,6-disulfonate (AQDS) as an electron shuttle. Bioproduction of Fe(II) was determined by ferrozine analysis. The unreduced and bioreduced solids were characterized by Mossbauer spectroscopy, X-ray diffraction and transmission electron microscopy. The extent of Fe(III) reduction in the bulk Fithian illite was enhanced by the presence of AQDS (73%) with complete reduction of jarosite and goethite and partial reduction of illite. Mossbauer spectroscopy and chemical extraction determined that 21-25% of illite-associated Fe(III) was bioreduced. The extent of bioreduction was less in the absence of AQDS (63%) and only jarosite was completely reduced with partial reduction of goethite and illite. The XRD and TEM data revealed no significant illite dissolution or biogenic minerals, suggesting that illite was reduced in the solid state and biogenic Fe(II) from jarosite and goethite was either released to aqueous solution or adsorbed onto residual solid surfaces. In contrast, only 1% of the structural Fe(III) in Muloorina illite was bioreduced. The difference in the extent and rate of bioreduction between the two illites was probably due to the difference in layer charge and the total structural Fe content between the Fithian illite (0.56 per formula) and Muloorina illite (0.87). There may be other factors contributing to the observed differences, such as expandability, surface area and the arrangements of Fe in the octahedral sheets. The results of this study have important implications for predicting microbe-induced physical and chemical changes of clay minerals in soils and sediments.