DFR Model Saline Seep to explore the potential for Martian colonization by Earth microorganisms

While life on Mars, extinct nor extant, has not been found, there exists the possibility of Earth-based microorganisms contaminating the Red Planet during rover expeditions and human exploration. To begin testing for potential establishment of microbes on Mars, a simplified drip flow reactor (DFR) laboratory model of a Martian saline seep was designed and inoculated with soil from Hailstone Basin, a terrestrial saline seep in Montana (USA). The seep was modeled as a sand-packed drip flow reactor at room temperature fed media with either 1 M NaCl or 1 M MgSO4 and high- or low-carbon conditions. The effects of growth under ambient air vs. CO2 and light vs. dark conditions were also investigated. Endpoint 16S rRNA gene community analysis was conducted using the Illumina Miseq paired-end v3 600-cycle kit and universal 16S V4 primers 515f/r806b. Sequencing results indicated significant selection of halotolerant microorganisms by the media. Model communities were dominated by Halomonas sp., and several known opportunistic pathogens to humans. These models provide an important foundation for identifying microbes that may contaminate spacecraft and be able to colonize Martian saline seeps and will be vital to informing spacecraft assembly cleanroom sterilization procedures.