Radiotolerance of microorganisms isolated from radiation fields on a university campus: Implications for shallow subsurface growth of microorganisms on Mars

摘要

The surface of Mars is exposed to higher levels of solar and galactic cosmic ray irradiation than Earth due to its very weak magnetic field. Thus, microorganisms that could possibly survive in the shallow subsurface of Mars would likely be radiotolerant. To better understand microorganisms that might reside in this environment of Mars, a number of isolates were obtained from the area around a gamma-radiation source, ~(137)Cs, located on the UMR campus. Radiation sensitivity assays were performed on the isolates as well as on the common bacterium, E. coli. All the organisms tested were able to withstand exposures up to 20 Gy. The E. coli control did not survive exposures of 200 Gy, while the isolate designated 1B-1 could. Another isolate, Cont-1, also withstood this exposure. Each of the isolates produced white growth on solid medium and their cells are rod-shaped. The study of these isolates and similar organisms could enhance our knowledge of these unique extremophilic bacteria and might provide insight into the microorganisms that could be present in the shallow subsurface of Mars.