Title: Tropical forest soil microbial communities couple iron and carbon biogeochemistry
Author: Dubinsky, Eric A.; Silver, Whendee L.; Firestone, Mary K.
Source: Ecology. 91(9):2604-2612.
Description: We report that iron-reducing bacteria are primary mediators of anaerobic
carbon oxidation in upland tropical soils spanning a rainfall gradient (3500–5000 mm/yr) in
northeast Puerto Rico. The abundant rainfall and high net primary productivity of these
tropical forests provide optimal soil habitat for iron-reducing and iron-oxidizing bacteria.
Spatially and temporally dynamic redox conditions make iron-transforming microbial
communities central to the belowground carbon cycle in these wet tropical forests. The
exceedingly high abundance of iron-reducing bacteria (up to 1.2 3 109 cells per gram soil)
indicated that they possess extensive metabolic capacity to catalyze the reduction of iron
minerals. In soils from the higher rainfall sites, measured rates of ferric iron reduction could
account for up to 44% of organic carbon oxidation. Iron reducers appeared to compete with
methanogens when labile carbon availability was limited. We found large numbers of bacteria
that oxidize reduced iron at sites with high rates of iron reduction and large numbers of iron
reducers. The coexistence of large populations of iron-reducing and iron-oxidizing bacteria is
evidence for rapid iron cycling between its reduced and oxidized states and suggests that
mutualistic interactions among these bacteria ultimately fuel organic carbon oxidation and
inhibit CH4 production in these upland tropical forests.
Keywords: bacteria, carbon cycling, iron reduction, Luquillo Mountains, methanogenisis, microbial
ecology, Puerto Rico, tropical forest soils
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Dubinsky, Eric A.; Silver, Whendee L.; Firestone, Mary K. 2010. Tropical forest soil microbial communities couple iron and carbon biogeochemistry. Ecology. 91(9):2604-2612..