Interactions of U(VI) with members of a microbial consortium recovered from a uranium mining waste pile.

Treatments of a soil sample from a uranium mining waste pile with uranyl nitrate led to a shifting in the crenarchaeal populations from subgroup 1.1a to 1.1b. Efforts to culture members of these Crenarchaeota resulted in an enrichment of a mixed microbial consortium consisting of representatives of 1.1b Crenarchaeota and Firmicutes.
In this study interactions of U(VI) with a pure culture of Paenibacillus sp. JG35+U4-B1 isolated from the mentioned consortium were studied by using a combination of wet chemistry and microscopic methods. Preliminary analyses on U sorption showed that the Paenibacillus strain studied accumulated up to 85 mg U/g dry biomass from a solution with an initial uranium concentration of 120 mg U/l. Live/Dead cell staining indicated that less than 10% of the U-treated cells were viable. Transmission electron microscope (TEM) analyses showed that the cells of the isolated strain accumulated uranium intracellularly as needle-like fibrils, and also at the cell surface. Energy dispersive X-ray (EDX) analysis of these U accumulates demonstrated the presence of U and P indicating that in both cases the phosphate groups are, probably, the main functional binding sites for U(VI).
Efforts to culture other strains from the mentioned consortium and especially of the yet to be cultured 1.1b-Crenarchaeota are in progress in our laboratory. Because our results indicated that these archaeal populations are strongly induced by the addition of U(VI) the study of these organisms is of importance for understanding the natural behavior of U in soils and also for remediation of contaminated sites.