Flowthrough of239PU and55FE during RNA extraction.

Analysis of gene expression has become an important tool in understanding low-dose effect mechanisms of ionizing radiation at the cellular level. Metal binding to nucleic acids needs to be considered when interpreting these results, as some radioactive metals, particularly actinides, may produce free radicals and cause oxidative stress damage via chemical means at rates much higher than free radical formation related to their radiological properties. Bacteria exposedin situto low dose rates of plutonium-239 (239Pu) and iron-55 (55Fe) were previously analysed for gene expression. The work herein was motivated by an interest in more precisely identifying the distribution of radionuclides in these bacteria as well as the practical need to ensure appropriate transport and handling of the associated ribonucleic acid (RNA) extractions. RNA extractions were performed on bacteria growth media with and without bacteria cells (i.e. with and without RNA) at several different concentrations of239Pu and55Fe to inform the level of specificity of the extraction membrane as well as provide insight into internal (uptake) vs external (sorption) accumulation of these radionuclides in bacteria cells. Results of the study suggest that239Pu and55Fe detected in RNA extraction samples during long term cell studies is the result of binding to RNA prior to the time of extraction, as opposed to flow through or binding after cell lysis, and it highlights the practical importance of nucleic acid sample characterization to radiation protection more generally.

Accumulation of radio-iron and plutonium, alone and in combination, inPseudomonas putidagrown in liquid cultures.

The impact of low doses of ionising radiation on biological and environmental systems have been historically difficult to study. Modern biological tools have provided new methods for studying these mechanisms but applying these tools to a dose-response relationship may require refinement of dosimetric techniques that incorporate a detailed understand of radionuclide accumulation in biological cells, particularly when assessing the impact of low doses of ionising radiation. In this workPseudomonas putida (KT2440) grown in liquid culture was exposed to low dose rates (10-20 mGy d-1) of239Pu and55Fe, both alone and in combination, for a period of 20 days, and the accumulation of239Pu and55Fe in cell pellets was analysed via liquid scintillation counting. The study also considered of cells grown with239Pu and stable Fe (primarily56Fe). In addition to the analysis of cell pellet and media samples, this work includes analysis of the radiological content of ribonucleic acid extraction samples to examine uptake of radionuclides. Results indicate that239Pu inhibited the uptake of55Fe, and that the presence of stable and radioactive isotopes of Fe in cultures may promote pathways for Fe accumulation that are used by239Pu. The work herein provides foundational insight into future dosimetric models for our work with environmental bacteria.