Molecular profile of micronutrient-producing microorganisms following Martian mission-relevant ionizing radiation dose rate exposure

This study evaluated the radiation tolerance, biomass production, vitamin biosynthesis, and whole-proteome response of three edible extremotolerant microorganisms, i.e., Debaryomyces hansenii DSM 3428, Bacillus subtilis DSM 10, and Limosilactobacillus reuteri DSM 20016, under a Martian mission-relevant ionizing radiation dose rate. Cultures were exposed to Martian cruise and Martian surface dose rates of gamma ionizing radiation, using γ-rays of a ⁶⁰Co source. Biomass yield and riboflavin content of irradiated cultures were analyzed. Proteomic analyses were conducted for the bacteria B. subtilis and L. reuteri, for which well-annotated reference genomes and proteomes were available. Also, post-irradiation regrowth characteristics were tested. D. hansenii and B. subtilis showed no significant impairment in growth rate post-irradiation, biomass production, or riboflavin synthesis during chronic exposure, and normal post-irradiation regrowth, similar to non-exposed cultures. In contrast, L. reuteri exhibited a higher radiation sensitivity, with a reduced biomass yield in the irradiated cultures, and an altered post-irradiation growth profile.