Microbial Community Composition in Baseline and Post-Mining Core Samples at an in-Situ Recovery (ISR) Uranium Mine.

Success of restoration after in situ recovery (ISR) uranium mining depends upon many factors, including the geochemical water-rock interactions as well as microbial processes.  Very little information is available on the native microbial community in and around the mined ore body, but this data could inform remediation decisions for the aquifer, especially bioremediation.  As part of a larger study characterizing the pre-mining baseline and the effects of ISR on a sandstone-hosted roll front deposit in Wyoming, we have compared microbial communities of pre-mining and post-mining cores at various depths using 454-pyrosequencing of the 16S rRNA gene.  Cores were collected in two mine units using sterile techniques.  One mine unit is being developed for ISR, but has not undergone any active injection, providing a baseline for pre-mining conditions.  The second mine unit has been mined, and is currently undergoing restoration (groundwater sweep), and serves as a post-mining comparison.  Samples for DNA analysis were frozen on-site and stored at -80°C.  Core samples were simultaneously taken from the same depths at both sites for geochemical and mineralogical characterization.  In general, low biomass is recovered from the samples, and mineralogical heterogeneity is present in the aquifer, which in turn affects the diversity of organisms present.  This work provides insight into changes in microbial community composition, a previously uncharacterized aspect of ISR mining, and highlights the potential role of microorganisms in affecting the fate and transport of uranium.