Microbial characteristic and bacterial community assessment of sediment sludge upon uranium exposure

The microbial characteristics and bacterial communities of sediment sludge upon different concentrations of exposure to uranium were investigated by high solution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and high-throughput sequencing. After exposure to initial uranium concentrations of 10-50 μM for 24 h in synthetic wastewater, the removal efficiencies of uranium reached 80.7%-96.5%. The spherical and short rod bacteria were dominant in the sludge exposed to uranium. HRTEM-EDS and XPS analyses indicated that reduction and adsorption were the main mechanisms for uranium removal. Short-term exposure to low concentrations of uranium resulted in a decrease in bacterial richness but an increase in diversity. A dramatic change in the composition and abundances of the bacterial community were present in the sediment sludge exposed to uranium. The highest removal efficiency was identified in the sediment sludge exposed to 30 μM uranium, and the dominant bacteria included Acinetobacter (44.9%), Klebsiella (20.0%), Proteiniclasticum (6.7%), Enterobacteriaceae (6.6%), Desulfovibrio (4.4%), Porphyromonadaceae (4.1%), Comamonas (2.4%) and Sedimentibacter (2.3%). By comparison to the inoculum sediment sludge, exposure to uranium caused a substantial difference in the majority of bacterial abundance.