The interaction between haloarchaea and their viruses

The research findings in this thesis provide a first insight into the interaction between viruses and single-celled archaea. Archaea are common microorganisms that can survive in the most extreme places on earth, for instance in hot springs, salt lakes or in ‘black smokers’ at the bottom of the ocean. In addition, archaea also live in less extreme conditions such as the intestines of humans. Archaea, like bacteria and eukaryotes, can be infected by viruses. These viruses have very diverse forms, for example that of a bottle, and little is known about their infection mechanism. Using microscopy and molecular biological techniques, this thesis studies the interaction between salt-loving archaea (halophiles) and their viruses in molecular detail. Thus, it could be shown that a virus with a head and a tail, first binds to the host upside down, before the virus turns over and delivers the genetic material. In addition, it describes how infection with a lemon-shaped virus can cause the archaea to build large clusters, where they bind to each other with multiple cells, presumably as a defense mechanism against the virus. These results show that the infection mechanisms of viruses from archaea have unique properties and are clearly distinct from those of bacteria and eukaryotes. Common properties of infection have also been found, contributing to the discovery of universal viral infection strategies.
Since archaea are probably closely related to the first life forms on early Earth, research on their viruses contributes to unravelling the origin and evolution of all viruses.