Space agencies, such as NASA, abide by Planetary Protection policies dedicated to preserving the scientific integrity of missions, as well as avoiding contamination of foreign bodies and adverse changes to Earth. Thus, the NASA Standard Assay quantifies heat-tolerant microbes to meet bioburden requirements. Microorganisms collected by the Assay are cultivated to purity and stored in frozen stocks. Bacteria collected from the Mars Exploration Rover and Phoenix missions were revived, then their genomic DNA extracted, 16S rRNA gene amplified and sequenced. Based on the sequences, 101 isolates from the MER craft and 52 isolates from the Phoenix Fairing were identified. Bacillus and Bacillus-like genera comprise over 50% (77 isolates), and Staphylococcus comprise 23% (35 isolates) of the studied isolates. Additionally, low sequence identity (<97%) suggests 4 putative novel species in the Bacillus, Paenibacillus, and Virgibacillus genera. Further biochemical tests will be performed to understand their metabolism and characterize novel species. Novel Paenibacillus species have an uncommon ridge cellular morphology, are able to grow at temperatures ranging from 25°C to over 50°C, and demonstrate unique carbon utilization. The elucidated diversity and physiology enhance microbial reduction techniques and build a bank of false-positives for future missions.

Contributors: Garrett Smith, Wayne Schubert, Stephanie Smith, Andrzej Paszczynski, James N. Benardini Affiliation: Jet Propulsion Laboratory, California Institute of Technology