Metabolic and genomic characteristics of bank voles exposed to radionuclides

Abstract

Organisms defend against external disturbances using various metabolic and genomic methods. Organisms experience stress when the disturbances grow severe enough to debilitate survival or reproduction. Low dose ionising radiation of environmental radionuclides is a form of contamination whose long-term metabolic and genomic effects on wild populations on the molecular level are not well understood. In this thesis I assess the metabolic and genomic consequences of inhabiting an environment polluted by radionuclides derived from the 1984 nuclear accident of Chernobyl, Ukraine, in the bank vole (Myodes glareolus) using techniques such as quantitative PCR, RNA-sequencing, 16S amplicon sequencing of gut microbiota, high precision liquid chromatography and gut tissue histology. I show that environmental radionuclides elicit expression changes in DNA repair mechanisms, fatty acid energy metabolism and mitochondrial function, which may facilitate oxidative balance. I also show that direct impact of radiation on the host rather than indirect effects through changes in gut microbiota composition better explain the observed metabolic changes. Moreover, bank voles exposed to radiation show immunosuppression and reduced mucus production in the colon, which may increase risk of infection. Furthermore, I show that voles exposed to radionuclides exhibit higher ribosomal DNA copy number, possibly improving genomic stability. Overall, inhabiting an environment contaminated by radionuclides possibly impacts metabolic and other regulatory mechanisms, causing diverse symptoms. Study of wildlife’s responses and its capabilities to survive anthropogenic disturbances continues to increase in importance along with increase in human population and land use.