Microbiology of extreme radiation environments

This seminar will be an overview of my PhD work covering microbial survival in high and ultra-low radiation environments. 

The high-radiation experiments focus on the radiation environments and resulting photochemistry in space and the Martian surface and how this might influence habitability. Photochemical reactions involving Martian compounds iron oxide, hydrogen peroxide and perchlorate were irradiated with shortwave UV in the presence of microbes to evaluate the effect on their viability. Iron and hydrogen peroxide are known components of the Photo-Fenton reaction which produces reactive oxygen species, whilst perchlorates are strong oxidants that can be activated by ionising radiation. The results of the photochemical experiments tie in to the post-flight analysis of the European Space Agency’s EXPOSE-R2 mission, which enabled us to send microbes to the outside of the International Space Station. These experiments were focussed on testing microbes’ ability to survive the multiple stresses of space, some of which in the presence of Martian analogue soil. 

At the opposite end of the spectrum, not much is known about the effect of ultra-low radiation on cells’ viability. Ongoing experiments in the underground lab at Boulby mine are testing the current Linear Non-Threshold and Hormetic models by measuring the effect of ultra-low radiation environments on microbial growth and stress recovery. Understanding biological effects of the ‘Z-axis’ of radiation is important not only from a fundamental research point of view but also informs us on potentially universal physical limits to life and habitability.