Diversity and Characterization of Sulfate-Reducing Bacteria in Groundwater at a Uranium Mill Tailings Site

Abstract

Microbially mediated reduction and immobilization of U(VI) to U(IV) plays a role in both natural attenuation and accelerated bioremediation of uranium-contaminated sites. To realize bioremediation potential and accurately predict natural attenuation, it is important to first understand the microbial diversity of such sites. In this paper, the distribution of sulfate-reducing bacteria (SRB) in contaminated groundwater associated with a uranium mill tailings disposal site at Shiprock, N.Mex., was investigated. Two culture-independent analyses were employed: sequencing of clone libraries of PCR-amplified dissimilatory sulfite reductase (DSR) gene fragments and phospholipid fatty acid (PLFA) biomarker analysis. A remarkable diversity among the DSR sequences was revealed, including sequences from ␦-Proteobacteria, gram-positive organisms, and the Nitrospira division. PLFA analysis detected at least 52 different mid-chain-branched saturate PLFA and included a high proportion of 10me16:0. Desulfotomaculum and Desulfotomaculum-like sequences were the most dominant DSR genes detected. Those belonging to SRB within ␦-Proteobacteria were mainly recovered from low-uranium (<302 ppb) samples. One Desulfotomaculum-like sequence cluster overwhelmingly dominated high-U (>1,500 ppb) sites. Logistic regression showed a significant influence of uranium concentration over the dominance of this cluster of sequences (P ‫؍‬ 0.0001). This strong association indicates that Desulfotomaculum has remarkable tolerance and adaptation to high levels of uranium and suggests the organism's possible involvement in natural attenuation of uranium. The in situ activity level of Desulfotomaculum in uranium-contaminated environments and its comparison to the activities of other SRB and other functional groups should be an important area for future research.Microbially mediated reduction of redox-sensitive metals offers the potential to remediate metal-contaminated groundwater in situ. Sulfate-reducing bacteria (SRB) are important members of microbial communities involved in such metal reduction and occur in a variety of environments, including oiland gas-bearing formations, soils, and domestic, industrial, and mining wastewaters (39). Although traditionally considered obligate anaerobes, observations of sulfate reduction occurring in the aerobic environment reported in the last 15 years have demonstrated a much larger ecological range of the SRB than previously thought (5, 6, 13). The dissimilatory sulfate-reducing bacteria in particular are environmentally ubiquitous, are found over an extensive range of pH and salt concentrations, and exhibit a superior ability to reduce and accumulate metals (16, 30,

Bacterial community succession during in situ uranium bioremediation: spatial similarities along controlled flow paths

“…Diversity and community function Microbial communities have been extensively characterized at uranium-contaminated sites (Abdelouas et al, 2000;Chang et al, 2001Chang et al, , 2005Elias et al, 2003;Nevin et al, 2003;Vrionis et al, 2005) including the OR-FRC (Yan et al, 2003;North et al, 2004;Fields et al, 2005Fields et al, , 2006Akob et al, 2007). In general, it is assumed that bacterial diversity will depend upon the degree of contamination and will change in structure and Partition of the total variation into six components: unexplained variation; 'pure' temporal variation; 'shared' variation between environment and time; 'pure' environmental variation; 'shared' variation between environment and space; and 'pure' spatial variation.…”

Characterization of NaCl tolerance in Desulfovibrio vulgaris Hildenborough through experimental evolution

“…In addition, SRB have been identified as culprits in the biocorrosion of ferrous metal installations in the petroleum industry and concrete structures in wastewater collection systems (Muyzer and Stams, 2008;Zhou et al, 2011). Effective reduction of highly toxic Cr (VI) or U (VI) to less toxic Cr (III) or U (IV) by D. vulgaris Hildenborough has been reported (Lovley et al, 1993;Lovley and Phillips, 1994;Elias et al, 2004), and D. vulgaris was found to exist in uranium (VI) contaminated field site (Chang et al, 2001). High NaCl concentration is also present in several DOE (Department of Energy) sites contaminated with toxic metals.…”

Geochemical evolution of uraniferous soda lakes in Eastern Mongolia

“…These high concentrations are attributed to fallout from above ground nuclear weapon testing in Nevada and New Mexico (Simpson et al 1980). The high abundance of the ordinarily insoluble actinides in the soda lake is attributed to complexation with carbonates that dramatically increases solubility and inhibits chemical removal from the water column (Chang et al 2001). Uranium concentrations from sediments from a desiccated soda lake in central Mongolia were recently found to have extremely high concentrations of U (U=1500µmol kg -1 , 350 ppm U) (Markwitz et al 2008).…”