Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

At this project the effects of low doses of radionuclides and heavy metals on the metabolic activity of microorganisms was assessed, using the state of the art Thermal Activity monitor microcalorimeter, TAM(III), as a novel monitoring tool in this study. Therefore, the toxicity was measured as the metabolic response for these low doses reflected by bacterial growth thermograms. The bacterial strain used in this project, Paenibacillus sp. JG-TB8, was isolated from a soil sample of the uranium mining waste pile “Haberland” (Johanngeorgenstadt, Saxony, Germany) by Thomas Reitz [4]. This bacterial strain was exposed to different concentrations in the range of micromolar of Eu(III) and U(VI) salts. Thetoxicity of europium chloride (Eu(III)Cl3) as a heavy metal was reflected by the thermogram as a decrement of its maximal heat flow. In contrast, the effect of the uranium salts was more complicated. It showed a strong dependence on temperature and pH. Correlation of the degree of toxicity with concentration of the uranium salt was observed strongly at 30 °C in R2A medium, while it showed more constructive effect related to the usage of uranium as energetic source for the metabolic activity of the PB at 20°C. The mentioned thermograms showed that the general toxic effect of uranium is present but does not scale systematically with the applied concentrations. The data reveal that the thermal signature of a contaminant is unique for each concentration.