Extreme colds provoke the synthesis of DNA protection proteins that have unique structures that grant stability

For worlds beyond Earth, potentially habitable regions will likely share environmental hallmarks of the Arctic Ocean where subzero conditions have driven the evolution of organisms capable of withstanding extreme cold temperatures and high salinities. Understanding the role of these environmental pressures on the genetic structure and translational capacity of microorganisms occupying these areas could yield methods for identifying potential biosignatures on other planets, providing insight on ice-covered refugia during Snowball Earth scenarios and understanding on how microbes overwinter in Arctic sea ice. One marine organism of interest is the cold-loving bacterium Colwellia psychrerythraea strain 34H (Cp34H), with activity reported down to -20°C, a wide range of growth temperatures (18°C to -12°C), and an array of unique cold-adapted proteins. Here I present results on how Colwellia reprioritizes its cellular functions through proteomic expression after incubations of up to 6 months in either seawater or high-salinity brines at temperatures of -5°C and -10°C. Data was obtained for activity (by tritiated leucine incorporation assay), viability (by most probable number (MPN) viability testing) and proteomic signature (by mass spectrometry). Based on identified proteomic signatures, Cp34H prioritizes DNA stability and protection as temperature decreases, with the variable of salinity influencing the cellular response to iron acquisition. Thermal proteome profiling was also conducted on these cells to identify stable proteins that are prioritized to maintain a functional cell, through structural stability and or DNA integrity maintenance. These findings yield insight into how the genetic structure of microbes influences their whole cell functionality in extreme cold environments, shaping the search for potential biosignatures on extraterrestrial environments.