Iron reduction and alteration of nontronite NAu-2 by a sulfate-reducing bacterium
YI-LIANG LI,1 HOJATOLLAH VALI,2,3 S, KELLY SEARS,3
JOHN YANG,4 BAOLIN DENG,5 and CHUANLUN L. ZHANG1
1Savannah
River Ecology Laboratory, University of Georgia, Aiken, South Carolina
29803, USA
2Department of Anatomy and Cell Biology/Department of Earth
and Planetary Sciences, McGill University, Montreal, Quebec H3A 2B2 Canada
3Facility for Electron Microscopy Research, McGill University,
Montreal, Quebec H3A 2B2 Canada
4Center for Environmental Sciences, Lincoln University, Jefferson
City, Missouri 65201, USA
SDepartment of Civil & Environmental Engineering, University
of Missouri, Columbia, Missouri 65211, USA
(Received June 3, 2003; accepted in revised form March 3, 2004) .
Abstract-Iron-rich clay minerals are abundant in the
natural environment and are an important source of iron for microbial
metabolism, The objective of this study was to understand the mechanism(s)
of enhanced reduction of Fe(III) in iron-rich 2:1
clay minerals under sulfate-reducing conditions, In particular, biogenic
reduction of structural Fe(III) in nontronite NAu-2, an Fe-rich smectite-group
mineral, was studied using a Desulfovibrio spp. strain G-11 with
or without amended sulfate, The microbial production of Fe(II) from NAu-2
is about 10% of total structural Fe(III) (30 mM) when Fe(III) is available
as the sole electron acceptor. The measured production of Fe(II), however,
can reach 29% of the total structural Fe(III) during sulfate reduction
by G-11 when sulfate (50 mM) is concurrently added with NAu-2, In contrast,
abiotic production of Fe(II) from the reaction of NAu-2 with Na2S (50
mM) is only ca, 7,5% of the total structural Fe(llI), The enhimced reduction
of structural Fe(III) by G- 11, particularly in the presence of sulfate,
is closely related to the growth rate and metabolic activities of the
bacteria, Analyses by X-ray diffraction, transmission electron microscopy,
and energy dispersive spectroscopy reveal significant changes in the structure
and composition of NAu-2 during its alteration by bacterial sulfate reduction.
G-11 can also derive nutrients from NAu-2 to support its growth in the
absence of amended minerals and vitamins, Results of this study suggest
that sulfate-reducing bacteria may playa more significant role than previously
recognized in the cycling of Fe, S, and other elements during alteration
of Fe-rich 2:1 clay minerals and other silicate minerals.
SREL Reprint #2778
Li, Y., H. Vali, S. K. Sears, J. Yang, B. Deng and C. L. Zhang. 2004. Iron reduction and alteration of nontronite NAu-2 by a sulfate-reducing bacterium. Geochimica et Cosmochimica Acta 68:3251-3260.
