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Applied and Environmental Microbiology, March 2001, p. 1328-1334, Vol. 67, No. 3
Department of Biological Sciences, The
University of Alabama, Tuscaloosa, Alabama
Received 10 August 2000/Accepted 11 December 2000
The influence of lithotrophic Fe(II)-oxidizing bacteria on patterns
of ferric oxide deposition in opposing gradients of Fe(II) and
O2 was examined at submillimeter resolution by use of an
O2 microelectrode and diffusion microprobes for iron. In
cultures inoculated with lithotrophic Fe(II)-oxidizing bacteria, the
majority of Fe(III) deposition occurred below the depth of
O2 penetration. In contrast, Fe(III) deposition in abiotic
control cultures occurred entirely within the aerobic zone. The
diffusion microprobes revealed the formation of soluble or colloidal
Fe(III) compounds during biological Fe(II) oxidation. The presence of
mobile Fe(III) in diffusion probes from live cultures was verified by
washing the probes in anoxic water, which removed ca. 70% of the
Fe(III) content of probes from live cultures but did not alter the
Fe(III) content of probes from abiotic controls. Measurements of the
amount of Fe(III) oxide deposited in the medium versus the probes
indicated that ca. 90% of the Fe(III) deposited in live cultures was
formed biologically. Our findings show that bacterial Fe(II) oxidation is likely to generate reactive Fe(III) compounds that can be
immediately available for use as electron acceptors for anaerobic
respiration and that biological Fe(II) oxidation may thereby promote
rapid microscale Fe redox cycling at aerobic-anaerobic interfaces.
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.3.1328-1334.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Suboxic Deposition of Ferric Iron by Bacteria in
Opposing Gradients of Fe(II) and Oxygen at Circumneutral pH
*
Corresponding author. Mailing address: Department of
Biological Sciences, University of Alabama, Tuscaloosa, AL 35487-0206. Phone: (205) 348-0556. Fax: (205) 348-1403. E-mail:
eroden{at}bsc.as.ua.edu.
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