Influence of low uranium concentrations on Peanibacillus sp. JG-TB8 using calorimetric metabolic monitoring


Influence of low uranium concentrations on Peanibacillus sp. JG-TB8 using calorimetric metabolic monitoring

Obeid, M.; Geissler, A.; Fahmy, K.; Oertel, J.

The qualitative and quantitative risk assessment of radiotoxicity in contaminated sites plays a key role in radioecological monitoring and for environmental protection. High doses of radioactivity are physically measurable in the near field of nuclear waste disposals. However, it is a major challenge to develop methods for low dose risk assessments typical for the far field, where transmission of radionuclides into the food chain may lead to health risks that are not detectable by conventional methods. To address this problem, a novel approach using metabolic monitoring of bacterial cell growth was established using the Thermal Activity Monitor (TAMIII; TA intruments, USA) as a multichannel microcalorimeter to identify the minimal dose of radionuclides that generates a measurable change in metabolic heat release. In this approach, the toxicity of a radionuclide was defined as a measurable effect on the metabolic activity of Peanibacillus sp. JG-TB8, a gram-positive bacterium isolated from a soil sample of the uranium mining waste pile “Haberland” (Johanngeorgenstadt, Saxony, Germany). Liquid cultures of this strain were exposed to micromolar concentrations of uranium (VI) salts and the metabolic heat release measured as a function of time and temperature. The non-radioactive "heavy metal stress" exerted by europium (Eu(III)) served as reference under the same conditions. Preliminary results show distinct and reproducible effects of uranium and europium on the time-dependent heat release already at 10 µM concentration. The toxicity of uranium and europium caused a decrease of maximal heat flow compared to control samples. In contrast to europium, for which the inhibitory action scales with concentration, uranium influences bacterial growth in a more complicated manner which strongly depends on temperature and pH, probably as a consequence of its different speciations. The results demonstrate that microcalorimetric monitoring is an extremely sensitive tool to investigate the influence of low heavy metal and radionuclide concentrations on the metabolic activity of microorganisms as shown here for Peanibacillus sp. JG-TB8.

Keywords: radiotoxicity; microcalorimetry; heavy metal

  • Poster
    Uranium biogeochemistry: transformations and applications, 11.-16.03.2012, Monte Verita, Ascona, Switzerland

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Publ.-Id: 16264