ISOLATION AND CHARACTERIZATION OF MANGANESE-OXIDIZING BACTERIA (MOB) FROM A FORMER URANIUM MINING DISTRICT, CONTAMINATED WITH HEAVY METALS

Heavy metal contamination in uranium mining sites is a common problem. The former uranium mining district in Eastern Thuringia, Germany, which was mined for four decades, was one of the most intensively mined and polluted sites. During mining the rocks consisting of low grade of uranium ores were leached leading to contamination with heavy metals forming secondary mineral enriched (SME) layers. The appearance of SME layers with manganese (Mn) and iron (Fe) oxides in the mining site provides a research platform on bioremediation and microbe-mineral interaction. This research focuses on the isolation and characterization of the manganese-oxidizing bacteria (MOB) from SME layers. Total digestion of the SME layer show high metal content of 18 mg/g, 55 mg/g and 73 mg/g soil of Mn, Al and Fe respectively. In contrast, the total carbon content of the SME layer is very low (0.28 g/kg soil) and pH is around 4.5. Culture dependent techniques revealed that total colony forming units (CFU) on modified K-medium from the SME layer is up to 10(7)/g soil. The initial full sequencing results of the isolates represent four different manganese oxidizers which belong to the genus Arthrobacter, Sphingomonas, Bacillus and Brevibacillus. The manganese oxidizers were tested using leukoberbelin blue, which reduces Mn oxides turning colonies to dark blue if manganese oxidation activity is present. Mn enrichment was further confirmed using LA-ICP-MS. Further perspectives will be to elucidate the microbial influence on the sorption of heavy metals to biogenic/synthetic Mn oxides.