NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Dissolution and reduction of magnetite by bacteriaMagnetite (Fe3O4) is an iron oxide of mixed oxidation state [Fe(II), Fe(III)] that contributes largely to geomagnetism and plays a significant role in diagenesis in marine and freshwater sediments. Magnetic data are the primary evidence for ocean floor spreading and accurate interpretation of the sedimentary magnetic record depends on an understanding of the conditions under which magnetite is stable. Though chemical reduction of magnetite by dissolved sulfide is well known, biological reduction has not been considered likely based upon thermodynamic considerations. This study shows that marine and freshwater strains of the bacterium Shewanella putrefaciens are capable of the rapid dissolution and reduction of magnetite, converting millimolar amounts to soluble Fe(II)in a few days at room temperature. Conditions under which magnetite reduction is optimal (pH 5-6, 22-37 degrees C) are consistent with an enzymatic process and not with simple chemical reduction. Magnetite reduction requires viable cells and cell contact, and it appears to be coupled to electron transport and growth. In a minimal medium with formate or lactate as the electron donor, more than 10 times the amount of magnetite was reduced over no carbon controls. These data suggest that magnetite reduction is coupled to carbon metabolism in S. putrefaciens. Bacterial reduction rates of magnetite are of the same order of magnitude as those estimated for reduction by sulfide. If such remobilization of magnetite occurs in nature, it could have a major impact on sediment magnetism and diagenesis.
Document ID
20040089550
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Kostka, J. E.
(University of Wisconsin Milwaukee 53204, United States)
Nealson, K. H.
Date Acquired
August 21, 2013
Publication Date
October 1, 1995
Publication Information
Publication: Environmental science & technology
Volume: 29
Issue: 10
ISSN: 0013-936X
Subject Category
Exobiology
Funding Number(s)
CONTRACT_GRANT: NAGW3-270
CONTRACT_GRANT: OCE-9212460
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Exobiology

Available Downloads

There are no available downloads for this record.
No Preview Available