Membrane remodeling is a fundamental and necessary process underlying proper functioning of cellular organisms in all three domains of life. Much of our knowledge on the mechanisms of membrane fusion and scission, two of the key steps during remodeling of biological membranes, comes from studies on enveloped eukaryotic viruses. By contrast, very little is known about these processes in prokaryotes of the domain Archaea, which have unique monolayer membranes composed of tetraether lipids spanning the entire thickness of the membrane. We have recently demonstrated that enveloped spindle-shaped viruses infecting hyperthermophilic acidophiles of the genus Sulfolobus are released from the cell by a process highly reminiscent of the budding of enveloped eukaryotic viruses, such as HIV-1, influenza virus and Ebola virus, which are prominent human pathogens. The ENVIRA project aims at using the spindle-shaped viruses, which represent one of the dominant virus groups in Archaea, as models to elucidate the molecular mechanisms of membrane remodeling during the entry and egress of these viruses.