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Applied and Environmental Microbiology, October 1998, p. 3791-3797, Vol. 64, No. 10
Department of Microbiology and Center for
Microbial Ecology, Michigan State University, East Lansing,
Michigan 48824,1 and
School of
Interdisciplinary Studies, Miami University, Oxford, Ohio
450562
Received 30 March 1998/Accepted 23 July 1998
Depth profiles of metals in Lake Vanda, a permanently ice-covered,
stratified Antarctic lake, suggest the importance of particulate manganese oxides in the scavenging, transport, and release of metals.
Since manganese oxides can be solubilized by manganese-reducing bacteria, microbially mediated manganese reduction was investigated in
Lake Vanda. Microbes concentrated from oxic regions of the water
column, encompassing a peak of soluble manganese [Mn(II)], reduced
synthetic manganese oxides (MnO2) when incubated
aerobically. Pure cultures of manganese-reducing bacteria were readily
isolated from waters collected near the oxic Mn(II) peak. Based on
phylogenetic analysis of the 16S rRNA gene sequence, most of the
isolated manganese reducers belong to the genus
Carnobacterium. Cultures of a phylogenetically representative strain of Carnobacterium reduced synthetic
MnO2 in the presence of sodium azide, as was seen in field
assays. Unlike anaerobes that utilize manganese oxides as terminal
electron acceptors in respiration, isolates of the genus
Carnobacterium reduced Mn(IV) via a diffusible compound
under oxic conditions. The release of adsorbed trace metals
accompanying the solubilization of manganese oxides may provide
populations of Carnobacterium with a source of nutrients in
this extremely oligotrophic environment.
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Manganese Reduction by Microbes from Oxic Regions
of the Lake Vanda (Antarctica) Water Column

*
Corresponding author. Mailing address: Department of
Microbiology, Giltner Hall, Michigan State University, East Lansing, MI
48824-1101. Phone: (517) 353-1796. Fax: (517) 353-8957. E-mail: tschmidt{at}pilot.msu.edu.
Present address: Department of Biology and Microbiology, University
of Wisconsin
La Crosse, La Crosse, WI 54601.
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