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Media type:
E-Article
Title:
Inhibition of NO 3 − and NO 2 − Reduction by Microbial Fe(III) Reduction: Evidence of a Reaction between NO 2 − and Cell Surface-Bound Fe 2+
Contributor:
Coby, Aaron J.;
Picardal, Flynn W.
Published:
American Society for Microbiology, 2005
Published in:
Applied and Environmental Microbiology, 71 (2005) 9, Seite 5267-5274
Language:
English
DOI:
10.1128/aem.71.9.5267-5274.2005
ISSN:
0099-2240;
1098-5336
Origination:
Footnote:
Description:
<jats:title>ABSTRACT</jats:title>
<jats:p>
A recent study (D. C. Cooper, F. W. Picardal, A. Schimmelmann, and A. J. Coby, Appl. Environ. Microbiol. 69:3517-3525, 2003) has shown that NO
<jats:sub>3</jats:sub>
<jats:sup>−</jats:sup>
and NO
<jats:sub>2</jats:sub>
<jats:sup>−</jats:sup>
(NO
<jats:sub>x</jats:sub>
<jats:sup>−</jats:sup>
) reduction by
<jats:italic>Shewanella putrefaciens</jats:italic>
200 is inhibited in the presence of goethite. The hypothetical mechanism offered to explain this finding involved the formation of a Fe(III) (hydr)oxide coating on the cell via the surface-catalyzed, abiotic reaction between Fe
<jats:sup>2+</jats:sup>
and NO
<jats:sub>2</jats:sub>
<jats:sup>−</jats:sup>
. This coating could then inhibit reduction of NO
<jats:sub>x</jats:sub>
<jats:sup>−</jats:sup>
by physically blocking transport into the cell. Although the data in the previous study were consistent with such an explanation, the hypothesis was largely speculative. In the current work, this hypothesis was tested and its environmental significance explored through a number of experiments. The inhibition of ∼3 mM NO
<jats:sub>3</jats:sub>
<jats:sup>−</jats:sup>
reduction was observed during reduction of a variety of Fe(III) (hydr)oxides, including goethite, hematite, and an iron-bearing, natural sediment. Inhibition of oxygen and fumarate reduction was observed following treatment of cells with Fe
<jats:sup>2+</jats:sup>
and NO
<jats:sub>2</jats:sub>
<jats:sup>−</jats:sup>
, demonstrating that utilization of other soluble electron acceptors could also be inhibited. Previous adsorption of Fe
<jats:sup>2+</jats:sup>
onto
<jats:italic>Paracoccus denitrificans</jats:italic>
inhibited NO
<jats:sub>x</jats:sub>
<jats:sup>−</jats:sup>
reduction, showing that Fe(II) can reduce rates of soluble electron acceptor utilization by non-iron-reducing bacteria. NO
<jats:sub>2</jats:sub>
<jats:sup>−</jats:sup>
was chemically reduced to N
<jats:sub>2</jats:sub>
O by goethite or cell-sorbed Fe
<jats:sup>2+</jats:sup>
, but not at appreciable rates by aqueous Fe
<jats:sup>2+</jats:sup>
. Transmission and scanning electron microscopy showed an electron-dense, Fe-enriched coating on cells treated with Fe
<jats:sup>2+</jats:sup>
and NO
<jats:sub>2</jats:sub>
<jats:sup>−</jats:sup>
. The formation and effects of such coatings underscore the complexity of the biogeochemical reactions that occur in the subsurface.
</jats:p>