Iron and Acid Adapted Strains of Halobacterium sp. NRC-1 obtained by Experimental Evolution. Halobacterium salinarum NRC-1

Haloarchaea are polyextremophiles capable of surviving a wide range of conditions inhibitory to most other microbial life. These conditions include but are not limited to salt stress, relatively high levels of UV irradiation, and desiccation. Their hardiness makes them an important model organism for the astrobiological community, and feasibility of microbial life on Mars has been brought into question. The purpose of this experiment was to assess haloarchaeal adaptation to iron and acid stress to better model how these microbes may adapt to some soil conditions that would be found on the surface of Mars. We conducted a laboratory evolution project in which we evolved Halobacterium sp. NRC-1 for 500 generations in a set of four conditions, with four evolving populations per condition. The four conditions correspond to a neutral pH control, mild acid stress (pH 6.3), iron and acid stress (600 μM ferrous sulfate, pH 6.3), and a iron stress condition (600 μM ferrous sulfate). 16 clones from generation 500 of evolution were isolated and their genomes sequenced, revealing patterns of high variability due to ISH element activity, large deletions, and loss of function mutations in proton pumps or transporters in multiple strains.