Phenotypic Changes Occurring in Escherichia coli Cells Previously Exposed to Simulated Microgravity

As humans explore space, bacteria will not only be present but will also be adapting to the extreme environment of space. During space missions astronauts have been shown to be immunocompromised which makes it imperative to understand the effects of space stressors (i.e., increased background radiation and microgravity(μg)) on bacteria. Current research has demonstrated an increase in virulence, biofilm formation, and antibiotic resistance. This research aims to identify multiple phenotypical changes that occur in E. coli cells exposed to simulated μg after 24 hours, 4 days, and 22 days. Specifically, this work observes changes in antibiotic resistance, osmotic tolerance, acidic tolerance, and oxidative stress. Preliminary experiments with antibiotic resistance utilizing the Kirby Bauer disc diffusion technique and the Minimum Inhibitory Concentration (MIC) method have demonstrated that exposure to simulated μg has a direct correlation of increased antibiotic resistance to some antibiotics with the increased duration of exposure. Additionally, increasing osmotic concentration inhibits the growth until four percent of sodium chloride and further increases have completely inhibited growth. These results can potentially be utilized for controlling growth of pathogenic bacteria in space. Additional studies using these two experiments as well as oxidative and pH stress will be explored.