Development of Martian saline seep models and their implications for planetary protection

Madelyn K Mettler; Hannah M Goemann; Rebecca C Mueller; Oscar A Vanegas; Gabriela Lopez; Nitin Singh; Kasthuri Venkateswaran; Brent M Peyton

doi:10.1016/j.bioflm.2023.100127

Development of Martian saline seep models and their implications for planetary protection

Biofilm. 2023 May 13:5:100127. doi: 10.1016/j.bioflm.2023.100127. eCollection 2023 Dec.

Authors

Madelyn K Mettler^{1

2}, Hannah M Goemann^{1

3}, Rebecca C Mueller^{1

4}, Oscar A Vanegas⁵, Gabriela Lopez⁶, Nitin Singh⁷, Kasthuri Venkateswaran⁷, Brent M Peyton^{1

2

8}

Affiliations

¹ Center for Biofilm Engineering, Montana State University, Bozeman, MT, USA.
² Department of Chemical and Biological Engineering, Montana State University, Bozeman, MT, USA.
³ Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA.
⁴ USDA Agricultural Research Service, Western Regional Research Center, Albany, CA, USA.
⁵ University of Georgia, Athens, GA, USA.
⁶ Georgia State University, Atlanta, GA, USA.
⁷ NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
⁸ Thermal Biology Institute, Montana State University, Bozeman, MT, USA.

Abstract

While life on Mars has not been found, Earth-based microorganisms may contaminate the Red Planet during rover expeditions and human exploration. Due to the survival advantages conferred by the biofilm morphology to microorganisms, such as resistance to UV and osmotic stress, biofilms are particularly concerning from a planetary protection perspective. Modeling and data from the NASA Phoenix mission indicate that temporary liquid water might exist on Mars in the form of high salinity brines. These brines could provide colonization opportunities for terrestrial microorganisms brought by spacecraft or humans. To begin testing for potential establishment of microbes, results are presented from a simplified laboratory model of a Martian saline seep inoculated with sediment 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 MgSO₄ or 1 M NaCl. Biofilms were established within the first sampling point of each experiment. Endpoint 16S rRNA gene community analysis showed significant selection of halophilic microorganisms by the media. Additionally, we detected 16S rRNA gene sequences highly similar to microorganisms previously detected in two spacecraft assembly cleanrooms. These experimental models provide an important foundation for identifying microbes that could hitch-hike on spacecraft and may be able to colonize Martian saline seeps. Future model optimization will be vital to informing cleanroom sterilization procedures.

Keywords: Biofilm; Drip flow reactor; Halophile; Mars; Next-generation sequencing.