Enterococcus faecalis, a human gut commensal bacterium, may be introduced to the Martian environment through crewed missions, and its survival capability poses potential risks to planetary protection and life detection tasks. This study simulated key Martian environmental parameters (low pressure:; hypoxic atmosphere: 95% CO₂; perchlorate: 20 mM MgClO₄) to reveal the unique adaptability of this bacterium under individual and combined stressors.
Experimental results showed that under single stressors, low pressure and low-concentration magnesium perchlorate increased its growth rate compared to Earth controls, while the Martian atmosphere significantly inhibited proliferation. Notably, it tolerated low pressure down to 200 Pa and exhibited a high perchlorate tolerance threshold of 200 mM. Even under combined stressors (700 Pa + 95% CO₂ atmosphere + 20 mM perchlorate), it survived by maintaining basal metabolic activity, breaking through the survival limitations of Martian multidimensional extremes. Mechanistic studies demonstrated that E. faecalis achieved environmental adaptation through synergistic effects of low pressure, hypoxia, and high-salt stress: low pressure alleviated perchlorate toxicity by enhancing membrane permeability, the Martian atmosphere induced metabolic remodeling (e.g., enhanced glycolysis) to compensate for energy supply, and perchlorate improved stress resistance by activating oxidative damage repair and osmotic pressure regulation systems. This "cross-protection" effect reveals microbial evolutionary strategies under multiparameter stress—utilizing molecular pre-adaptation triggered by individual environmental pressures to synergistically resist the cumulative damage of combined stressors.
This discovery not only challenges the current single-factor assessment framework for microbial tolerance thresholds in spacecraft sterilization standards but also provides scientific evidence for Martian life detection.

Enterococcus faecalis,Martian environmental simulation,Survival threshold,Planetary protection