THE ULTRAMICROBACTERIAL COMMUNITY OF THE URANIUM AND HEAVY METAL CONTAMINATED Y-12 AQUIFER

This research investigates the function and occurrence of the ultramicrobacterial (UMB) and ultra-small bacterial (USB) communities during an Emulsified Vegetable Oil (EVO) groundwater amendment. The EVO amendment was injected into the nitrate, heavy metal, and radionuclide contaminated shallow saprolite aquifer at the Y-12 Complex in Oak Ridge, Tennessee. Wells upgradient and downgradient of the injection were sampled for pH, specific conductance, dissolved oxygen, organic acids, anions, cations, metals, radionuclides, and hydraulic conductivity for five months post-injection. Groundwater was filtered through 0.2µm and 0.1µm filter membranes to separate bacterial communities by size. Bacterial DNA was extracted using modified methods for low DNA concentrations and 16s rRNA amplicons were sequenced on an Illumina Mi-seq. Improved transmission electron microscopy (TEM) methodologies for low concentrations of small cells in environmental samples and viscous EVO solutions yielded images of candidate UMB from the study site. Chemistry data indicates biologically-mediated degradation of EVO in the aquifer, as supported by increases in organic acids, the immobilization of metals, and the emergence of key bacterial functional groups in the larger size-fraction. Amplicon sequences indicate candidate USB are present, but further analysis of sequence data is being conducted to determine the significance of these organisms within the bioremediation process.