Date of Graduation


Document Type


Degree Name

Bachelor of Science in Biology

Degree Level



Biological Sciences


Ivey, Mack

Committee Member/Reader

Lessner, Daniel

Committee Member/Second Reader

Reeber, Joy

Committee Member/Third Reader

Wheeler, Jill


The NASA Office of Planetary Protection regulates the safe scientific exploration of other planets. Specifically, the office enacts rules to discourage interplanetary mission practices that would lead to the contamination of Earth-originating microbial life on other planets. Interplanetary contamination jeopardizes the potential to obtain reliable scientific evidence for extraterrestrial life. In coordination with this office, the biosignatures of potential colonizers of other celestials bodies are studied. Several organisms of Earth qualify as potential colonizers of other planets.

This experiment focused on the environment of Mars in particular. Two organisms were tested: Desulfovibrio arcticus and Desulfotalea psychrophila. Both are psychrotolerant or psychrophilic anaerobic bacteria isolated from the arctic circle that metabolize by reducing sulfates to sulfide. Due to these characteristics, they are prime candidates to survive on the Martian surface, where sulfates and carbon sources are present. Four carbon sources were tested in different percentages: 0.5%, 1%, 2%, 3% and 4% of dextrose, glycerol, sodium acetate, and isobutyric acid. The carbon sources on Mars are not yet known, but these represent four different lengths of carbon sources that could be found on Mars.

Based on the results of the experiment, the evidence supports the notion that D. arcticus was not able to metabolize any of the four carbon sources presented in any of the five different percentages. This could be due to suboptimal growth conditions or the complexity of the carbon sources themselves being incompatible with the growth of D. arcticus. However, the evidence indicates that D. psychrophila was able to metabolize some percentages of all carbon sources except for isobutyric acid. It was able to metabolize higher percentages of dextrose and lower percentages of glycerol and sodium acetate. The next project should be the investigation of other Martian conditions, such as temperature and pressure, in order to test the viability of the organisms in the Martian environment.


Mars, astrobiology, microbiology, molecular biology