More than half a century of nuclear activity has globally spread radionuclides in our environment, i.e. soil, water and food. Furthermore, the exposure to radionuclides is potentially increased by human activities via controlled and accidental releases by nuclear power facilities and medical activities. In addition, human activities can lead to an increased exposure to naturally occurring radioactive materials (NORM). Examples of such activities are mining and processing of ores, phosphate industries, production of natural gas or oil.
Microorganisms are often found in radionuclide-contaminated sites where they can influence radionuclide mobility, toxicity and distribution. Key processes are reduction, uptake and accumulation by cells, biosorption and complexation with proteins, polysaccharides and microbial biomolecules, and biomineralization with phosphates and carbonates. In turn, long-lived radionuclides can exert a permanent pressure on the prevailing microbial population. Consequently, fundamental understanding of the interaction between microorganisms and radionuclides is essential to correctly assess the microbial impact on the long-term behaviour of radionuclides in contaminated environments. Although the interaction of microorganisms with uranium is extensively studied, there is far less information about the cellular response of microorganisms to uranium exposure. Furthermore, there are only a limited number of studies investigating radionuclides other than uranium.
Cupriavidus metallidurans strains, which are mostly isolated from industrial sites linked to mining, metallurgic and chemical industries, are known for their resistance to a wide plethora of heavy metals. Moreover, type strain C. metallidurans CH34 is used as model organism to study metal resistance. The interaction of C. metallidurans with uranium (U238) and americium (Am241) has been studied, however, neither the genes or proteins involved nor the precise mechanism is known. Recently, we showed a strain-specific response and adaptation of C. metallidurans to uranium and evolved a strain in the laboratory to resist increased uranium concentrations.