Evaluation of the Salmonella type 3 secretion system (T3SS) as part of a protein production platform for space biology applications

As interest in space exploration and <i>in situ</i> resource utilization grows, the potential to leverage synthetic biology and engineered microorganisms has garnered significant attention. Microorganisms provide a robust and efficient biological chassis to demonstrate the human blueprint for advancing space biology. However, progress toward these applications is hindered by the limited access to space-like environments and a lack of knowledge about how unique environmental factors affect relevant microbial systems. To address these issues, we evaluated the <i>Salmonella</i> Pathogenicity Island 1 (SPI-1) type Ⅲ secretion system (T3SS) as a protein production platform for space applications. Using a NASA-designed microgravity-simulating bioreactor system, we investigated the effects of simulated microgravity on cell growth, stress response, and protein secretion <i>via</i> SPI-1 T3SS. Our results demonstrated increased stress responses in cells grown under simulated microgravity. However, the SPI-1 T3SS maintained its ability to secrete proteins directly into the extracellular space in a single step under simulated microgravity, simplifying downstream purification processes. These findings suggest that the SPI-1 T3SS is a viable candidate for future space biology applications.