Growth of Methanogens in the Presence of Perchlorate Salts: A Study for Possible Life on Mars

The Phoenix Lander collected soil samples from Mars, and it detected perchlorate salts in its analysis [1]. As oxidizing agents, perchlorates pose a threat to the hypothesis that there may be microbial life on Mars. Since Mars is very dry, perchlorate may continue to accumulate in the soil. If anaerobic methanogens inhabit Mars, then they must be able to grow in the presence of perchlorate salts. There were four species of methanogens tested in this project. The methanogens were first exposed to small concentrations of calcium perchlorate, and then they were gradually tested at higher concentrations. Growth was measured by the production of methane, which is a biomarker for metabolic activity. Each species responded in a unique way to the increasing concentrations of calcium perchlorate salts. The results showed that microorganisms that grow in minimal media had the lowest tolerance; while microorganisms that grow under increased levels of salt in their media could tolerate higher concentrations of calcium perchlorate