Astrobiology Workshop, Macquarie University July 12-13 2001

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Tolerance of Microbes to Simulated Space Conditions

Paul Martin (University of Southern Queensland)

Over the last few years examples of bacteria have been shown to survive the conditions of space, for example Bacillus subtilis survived for 6 years on the LDEF and Streptococcus mitus survived after 3 years after exposure to the conditions on the moon (Horneck, 1995; McKay 1998).

This study has two parts. The first is the design and integration of new and existing components to make an experimental chamber to simulate as far as practical space like conditions. The second is to test the viability of 4 chosen bacterial strains to these conditions. The 4 strains chosen were Bacillus subtilis (wild strain), Staphylococcus aureus ATCC 49476, Escherichia coli ATCC 25922 and Staphylococcus epidermidis ATCC 49134.

Each strain was air dried onto an aluminium or glass surface and exposed to a combination of vacuum (<2x10-5Pa), ultraviolet (UV) radiation and extremes in temperature (-184oC to +194oC). After exposure each microbe was tested for viability by recovering the air dried microbe from the inanimate surface and cultured onto nutrient media. Samples were kept for polymerase chain reaction (PCR) techniques in the cases of no growth. PCR is able to determine if any DNA has survived the exposure to space conditions.

It was found that they could survive the conditions of hard vacuum and extreme cold. However, unprotected bacteria when exposed to the UV and thermal radiation did not survive.