HR: 1340h
AN: B13A-1048    [Abstracts]
TI: High abundance and diversity of iron-reducing bacteria in wet tropical forest soils
AU: * Dubinsky, E A
EM: dubinsky@nature.berkeley.edu
AF: University of California, Department of Environmental Science, Policy and Management 137 Mulford Hall, Berkeley, CA 94720 United States
AU: Brodie, E L
EM: elbrodie@lbl.gov
AF: Lawrence Berkeley National Laboratory, Ecology Department , Berkeley, CA 94720 United States
AU: Andersen, G L
EM: GLAndersen@lbl.gov
AF: Lawrence Berkeley National Laboratory, Ecology Department , Berkeley, CA 94720 United States
AU: Silver, W L
EM: wsilver@nature.berkeley.edu
AF: University of California, Department of Environmental Science, Policy and Management 137 Mulford Hall, Berkeley, CA 94720 United States
AU: Firestone, M K
EM: mkfstone@nature.berkeley.edu
AF: University of California, Department of Environmental Science, Policy and Management 137 Mulford Hall, Berkeley, CA 94720 United States
AU: Firestone, M K
EM: mkfstone@nature.berkeley.edu
AF: Lawrence Berkeley National Laboratory, Ecology Department , Berkeley, CA 94720 United States
AB: In wet tropical forests, warm and damp conditions promote rapid oxygen consumption in soils that contain high concentrations of iron oxides. Ferric iron is often the most abundant terminal electron acceptor for bacteria in soil during frequent periods of oxygen depletion. Highly-weathered soils of the wet tropics are likely to support large populations of Fe(III) reducing microorganisms whose activity is consequential to soil mineralogy and geochemistry. We studied the diversity and abundance of Fe(III)-reducing bacteria along a 700 m elevation gradient with variable soil redox conditions in northeast Puerto Rico. Culturable iron-reducers were enumerated, isolated and identified using five different media that contained poorly-crystalline Fe(III) oxides as the terminal electron acceptor. Entire soil microbial communities were characterized along the gradient using high-density 16S rRNA gene microarrays capable of detecting 9000 different bacterial and archaeal taxa and assessing changes in their spatial abundance. Fe(III)-reducing bacteria spanned the Proteobacteria and Firmicutes and included many previously unidentified Fe(III) reducers. Populations of culturable iron reducers numbered 10⁸ to 10¹⁰ bacteria per gram soil, some of the highest numbers found in any soils or sediments, and population size increased significantly with elevation. These bacteria were dominated by both unclassified alpha- and gamma proteobacteria not previously known to reduce iron, in addition to delta-proteobacteria, such as the family Geobacteraceae, that are well-known Fe(III) reducers. The activity of this group of bacteria can affect biogeochemical cycles that are linked to iron and fundamental to tropical forest productivity, including phosphorus and carbon cycling.
DE: 0404 Anoxic and hypoxic environments (4802, 4834)
DE: 0410 Biodiversity
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0463 Microbe/mineral interactions
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
SC: Biogeosciences [B]
MN: Fall Meeting 2005