Enterobacter cloacae, a gram-negative bacterium commonly found in the human gut microbiota, poses potential health risks to astronauts in the unique environment of space flight. This study investigated the effects of payload shielding on E. cloacae in a short-duration, student-initiated, weather balloon flight experiment. Faraday fabric-based payload shielding did not impact the viability of the balloon flight samples. However, murine macrophage infection assays showed that shielded balloon flight E. cloacae had significantly improved intracellular survival compared to unshielded E. cloacae. Proteomic analysis demonstrated distinct profiles in shielded and unshielded samples, with a differential abundance of proteins involved in diverse biological processes. Specifically, decreased abundance of proteins involved in chemotaxis, DNA repair, replication, transcription, peptidoglycan synthesis, and proteolysis were observed in the Faraday fabric-based payload-shielded samples. In contrast, proteins associated with protein translation, transport, tricarboxylic acid cycle, fatty acid biosynthesis, and amino acid metabolism were increased in shielded conditions. This experiment provides a framework for which future long-duration balloon flight experiments can be designed, and the findings provide initial insights into the impact of payload shielding on E. cloacae physiology. Understanding the impact of the stratosphere on human gut microbiota is important for preserving human health during future space flight missions.
