Zusammenfassung
Host-virus co-evolution has been shown to be a major selection pressure driving evolution. This system has been well studied, but a newly discovered virophage, parasitizing on viruses, might change these dynamics. A virophage is able to co-infect the host and thus inhibiting the virus while replicating itself. While the interaction has been partly studied there is no experimental data on the dynamics or evolution of such a system. This thesis aims to tackle that by exploring the host-virus-virophage evolution with the marine flagellate Cafeteria roenbergensis, its virus CroV and the virophage Mavirus. Through experimental set-ups we allowed co-evolution and on-sided-evolution for the virus and virophage, these lineages were tested for fitness changes in different test environments by examining the impact on the host population. The evolved viruses resulted in an increase of the host population, which indicates a decrease of CroV infectivity, while the co-evolved Mavirus resulted in a decrease of the host population. This indicates the complexity the virophage adds to the host-virus system. This thesis was a first step in exploring it and establishing methods for further studies.
