Integrative analysis of <i>Geobacter</i> spp. and sulfate-reducing bacteria during uranium bioremediation
Enhancing microbial U(VI) reduction with the addition of organic electron donors is a promising strategy for immobilizing uranium in contaminated groundwaters, but has yet to be optimized because of a poor understanding of the factors controlling the growth of various microbial communities during bi...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2012-03-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/9/1033/2012/bg-9-1033-2012.pdf |
| Summary: | Enhancing microbial U(VI) reduction with the addition of organic electron donors is a promising strategy for immobilizing uranium in contaminated groundwaters, but has yet to be optimized because of a poor understanding of the factors controlling the growth of various microbial communities during bioremediation. In previous field trials in which acetate was added to the subsurface, there were two distinct phases: an initial phase in which acetate-oxidizing, U(VI)-reducing <i>Geobacter</i> predominated and U(VI) was effectively reduced and a second phase in which acetate-oxidizing sulfate reducing bacteria (SRB) predominated and U(VI) reduction was poor. The interaction of <i>Geobacter</i> and SRB was investigated both in sediment incubations that mimicked in situ bioremediation and with in silico metabolic modeling. In sediment incubations, <i>Geobacter</i> grew quickly but then declined in numbers as the microbially reducible Fe(III) was depleted whereas the SRB grow more slowly and reached dominance after 30–40 days. Modeling predicted a similar outcome. Additional modeling in which the relative initial percentages of the <i>Geobacter</i> and SRB were varied indicated that there was little to no competitive interaction between <i>Geobacter</i> and SRB when acetate was abundant. Further simulations suggested that the addition of Fe(III) would revive the <i>Geobacter</i>, but have little to no effect on the SRB. This result was confirmed experimentally. The results demonstrate that it is possible to predict the impact of amendments on important components of the subsurface microbial community during groundwater bioremediation. The finding that Fe(III) availability, rather than competition with SRB, is the key factor limiting the activity of <i>Geobacter</i> during in situ uranium bioremediation will aid in the design of improved uranium bioremediation strategies. |
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| ISSN: | 1726-4170 1726-4189 |