Microbes adapted to acid mine drainage as source for strains active in retention of aluminum or uranium

The use of microorganisms for the extraction of contaminants like solved metals from drainage or surface waters was investigated using strains adapted to a polluted environment at a former uranium mining site near Kauern, Eastern Thuringia, Germany. Soil respiration data showed increasing variation indicating stress response and hence need for adaptation. Thus, isolation of single strains was performed for more detailed analyses. Of the isolated fungi and bacteria (single-celled bacteria as well as filamentous actinobacteria), 15 were grown in mine drainage waters in order to test their capacity to retain (heavy) metals including rare earth elements and radioisotopes. Out of the 15 strains (respectively 5 single-celled bacteria, actinobacteria and fungi), 11 strains could grow in media containing acid mine drainage waters diluted by half which is representative of the conditions a few meters downstream of the entry point of the acid mine drainage. Two strains showed promising capacity for aluminum or uranium retention. Using rare earth elements as tracers, selective biosorption or uptake of heavy rare earth elements was prominent in one sample, a fungal isolate. The actinobacterial strains also showed capacity for bioremediation of contaminated seepage waters. Different reactions to single elements varying between all isolates indicate biologically controlled transport processes because such strong fractionation would not be expected from physico-chemical adsorption processes.