Selection favors cost-ordered adaptive mutational paths in a stress-magnitude-dependent manner.

Selection favors cost-ordered adaptive mutational paths in Escherichia coli depending on stress magnitude, with distinct mechanisms activated at different paraquat levels.

• Why it matters: Understanding how bacteria adapt to varying intensities of stress is crucial for insights into microbial resilience and could inform strategies to combat bacterial survival under stress conditions.
• What they did: Researchers conducted multiple adaptive laboratory evolution experiments with E. coli across different paraquat concentrations and genetic backgrounds, integrating multi-omic data and metabolic modeling to analyze adaptive strategies.
• The result: They found that low stress triggers blocking of polyamine transporters, while higher stress activates energy-intensive detoxification and efflux pathways, revealing a stress-dependent hierarchy of adaptive responses.