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, 137Cs, 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.
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