Simulated Microgravity Triggers Adaptation to Membrane Stress in E. coli REL606

Investigating the evolution of Escherichia coli in microgravity offers valuable insights into microbial adaptation to extreme environments. Here the effects of simulated microgravity (SµG) on gene expression and genome evolution of E. coli REL606, a strain evolved terrestrially for 35 years is explored. The transcriptomic changes for glucose-limited and glucose-replete conditions over 24 hours illustrate that SµG increased the expression of stress response and cell membrane-related genes, particularly under glucose-limited conditions. A machine learning model predicted that glucose-limited SµG impacts the cellular membrane, while glucose-replete SµG also inhibits protein synthesis at stationary phase. Longer term SµG culture under glucose-limited conditions led to accumulated mutations unique from the control culture, particularly in the mraZ and elyC genes, suggesting changes in peptidoglycan production. These findings highlight the physiological and genomic adaptations of E. coli to microgravity, offering a foundation for future research into the long-term effects of space conditions on bacterial evolution.