Abstract
<jats:p>Evaluating how microorganisms respond and tolerate space conditions is essential to ensure the safe access and exploration of space. This thesis investigates the risks associated with the contamination other planets with microbes originating from Earth, and how the human immune system responds to infections in space. The first part has showed how human-associated pathogenic bacteria interact with the immune system after exposure to space conditions and how regolith simulants impact human health. The second part focuses on the survival of environmental microorganisms capable of growth at subzero temperatures. The growth of such microbes is relevant to investigate the habitability of the icy moons of the solar system and to evaluate the risks associated with a contamination from Earth. The studies of this thesis have showed how the selected microorganisms can tolerate space conditions, and how genes in the selected yeast are regulated under extreme conditions. As a whole this work provides new microbial survival data and aims to improve the healthy access to space for humans.</jats:p>