Integrative analysis of <i>Geobacter</i> spp. and sulfate-reducing bacteria during uranium bioremediation

Abstract

<jats:p>Abstract. 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 Geobacter 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 Geobacter and SRB was investigated both in sediment incubations that mimicked in situ bioremediation and with in silico metabolic modeling. In sediment incubations, Geobacter 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 Geobacter and SRB were varied indicated that there was little to no competitive interaction between Geobacter and SRB when acetate was abundant. Further simulations suggested that the addition of Fe(III) would revive the Geobacter, 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 Geobacter during in situ uranium bioremediation will aid in the design of improved uranium bioremediation strategies.</jats:p>

Influence of Carbon and Microbial Community Priming on the Attenuation of Uranium in a Contaminated Floodplain Aquifer

“…This is apparent in the order of magnitude higher numbers of sulfate-reducing bacteria and methanogenic archaea observed on PR as compared with NR sediments (Figures 5). In silico modeling efforts predicting the response of the microbial community as a function of acetate addition in uranium-contaminated sediments indicate that iron bioavailability, as opposed to competition for acetate between iron-and sulfate-reducing bacteria is the primary factor limiting Geobacter activity in these sediments, and our PR microbial community dynamics support this model (Barlett et al 2012). However, the sediments used in our studies had similar initial Fe(II) and bioavailable Fe, yet the microbial dynamics in NR were very different than what would have been predicted by Barlett et al (2012) given the initial abundance of iron-and sulfate-reducing bacterial sequences.…”

A uranium bioremediation reactive transport benchmark

“…This was done to represent the recalcitrance of the dominant Ca-UO 2 -CO 3 species to bioreduction [20]. Note that the dependence of the sulfate rate law on the SRB biomass was necessary to progressively increase the sulfate bioreduction rate with time to match the field observations and transcriptomic evidence for sulfate bioreduction from the initiation of the biostimulation [21]. Biomass decay and a rate limit are other controls on the sulfate bioreduction rate (Eq.…”

Metagenome phylogenetic profiling of microbial community evolution in a tetrachloroethene-contaminated aquifer responding to enhanced reductive dechlorination protocols

“…These species are capable of direct interspecies energy transfer, a recently recognized characteristic of biofilms capable of bioremediation [28, 29]. Geobacter as well as SRB are detected during uranium bioremediation [30]. G. lovleyi can transfer cobamide to Dehalococcoides in culture, indicating that these species form an important metabolic link during ERD [31].…”