Stress-induced mutagenesis in Cupriavidus metallidurans strains

This thesis had a two-sided purpose: The first was to determine which processes & molecules are responsible for the TIMM-phenotype. TIMM stands for temperature-induced mortality and mutagenesis and was first seen when incubating Cupriavidus metallidurans CH34 on rich medium at 37 °C. Narrowing down the components that could induce TIMM was a first objective. Several amino acids were able to induce TIMM per tested strain, but different patterns arose between the tested strains. Inductors of TIMM seem independent of each other, one being the metabolization of the amino acids and the other being related to osmotic potential. Mitigation of TIMM was induced by adding neutral osmolytes, while the use of reactive oxygen scavengers scavengers had little to no effect. A time-lapse microscope experiment was performed to see if changes could be detected while TIMM was induced. Characteristics like cell-elongation, reproduction halting and cell-lysis were induced. The second purpose was to increase zinc-resistance in the C. metallidurans CH34 and AE104 strains. This was done by directed evolution, or growing the bacterium in medium with zinc concentrations above their respective minimal inhibitory concentration (MIC). Both strains were successfully evolved to resistances of 0,5 mM for AE104 and 26 mM for CH34 respectively.