Fig 3.

Frequencies of mutation to 4-azaleu^r of spores of different strains exposed to the full suite of simulated Martian conditions shielded (white hatched bars) and including UV radiation (gray bars). Data are averages and standard deviations (n = 3). The lowercase letters above the bars denote groups significantly different by ANOVA (P < 0.05). The spontaneous frequency of mutation to 4-azaleu^r of the wild-type strain (i.e., the mean spontaneous 4-azaleu^r mutation frequencies of strains 168, PY79, and PS832 ± the standard deviation) was (9.7 ± 3.6) × 10⁻⁷, in good agreement with previous data (35).