Supporting Information and Data for Viability and Motility of Escherichia coli under Elevated Martian Salt Stresses

This study investigates the effects of three Martian-relevant salts—sodium chlorate, sodium perchlorate, and sodium chloride—on the viability and motility of Escherichia coli, a model or-ganism for understanding microbial responses to environmental stress. (1) Background: These salts are abundant on Mars and play a crucial role in forming brines, one of the few sources of stable liquid water on the planet. (2) Methods: We analyzed the survivability in different salt concentrations using colony plating. Additionally, we performed a semi-automated motility analysis, analyzing microbial speeds and motility patterns. (3) Results: Our results show that sodium perchlorate is the most toxic, followed by sodium chlorate, with sodium chloride being the least harmful. Both survivability and motility were affected by salt concentration and ex-posure time. Notably, we observed a short-lived increase in motility at certain concentrations, particularly under sodium perchlorate and sodium chlorate stress, despite rapid declines in cell viability, suggesting a stress response mechanism. (4) Conclusions: Given that motility might enhance an organism's ability to navigate harsh and variable environments, it holds promise as a key biosignature in the search for life on Mars.