Iron is an essential nutrient for all living organisms. It plays a crucial role in the virulence of pathogenic bacteria as well as parasitic eukaryotes. Although iron is an abundant element in the host organism, it cannot be easily obtained by the parasite. The ability of parasites to induce disease depends largely on how efficient the mechanisms for iron acquisition have evolved. This thesis deals with the effect of iron on the virulence of Acanthamoeba castellanii. It is a free-living amoeba that, in exceptional situations, can cause fatal inflammatory brain disease or damage a person's vision. Culturing with mammalian cells allowed us to demonstrate the effect of iron on amoeba virulence using flow cytometry. Based on fluorescent labeling, we localized the protein AC_IDIP (Iron-Deprivation Induced Protein) in the cytosol. This protein was also isolated and a polyclonal antibody was raised against it and used to monitor the effect of iron availability on the AC_IDIP level. Using comparative proteomic analysis, it was possible to monitor changes in the A. castellanii proteome depending on the nutrient source. Altered levels of many proteins were detected under conditions where mammalian cells were the nutrient source. These were mainly cytoskeletal proteins. In contrast, the proportion of proteins..
