Assessment of DNA damage by cosmic rays and radiation

Abstract

We stand at the dawn of an extraordinary new space era, fuelled by ambitious plans to send humans not only to the Moon and Mars but also on deep space missions. As astronauts venture into the vast unknown for increasingly prolonged periods, the implications of long-term space travel remain obscure. The hostile environment of space poses a significant challenge, as high-energy radiation and microgravity conditions can cause DNA damage in astronauts. In August 2021, Malta sent its first bioscience experiment to the International Space Station. Building upon this milestone, a follow-up experiment was scheduled for July 2022 aiming to investigate the adaptation and changes in the microbiome induced by spaceflight. This undergraduate thesis aimed to explore the DNA damage caused by the radiation environment of low-Earth orbit. Skin microbiome samples from diabetic foot ulcers of type 2 Diabetes Mellitus patients were collected and split into three: Day 1 samples, ISS experimental samples and Earth-bound controls. Immediately after collection, Day 1 samples were processed for culture and analysed by 16S NGS. The ISS samples were sent to space and back. These remained in orbit for approximately 30 days aboard the ISS. During the same time duration, Earth-bound controls from the same specimen were exposed to the same temperature as that on the ISS. After returning to the ground, the microbiome samples were cultured and analyzed for radiationinduced DNA damage by the quantitative measurement of 8-OH-dG followed by variant analysis of 16S NGS. The concentration of 8-OH-dG was the same across both missions (p = 0.218) and even separately for Maleth I (p = 0.818) and for Maleth II (p = 0.057). However, there was a higher prevalence of DNA variations in the ISS samples compared to Earth samples, specifically single nucleotide polymorphisms as observed in the 16S region tested in the microbiomes. This raises concerns about the potential of microbial adaptation in space resulting in increased virulence. Oppositely, bacterial variations acquired through space-based experiments have the potential to contribute to the treatment of diabetic foot ulcers which are considered a burden both for diabetic patients, as well as for healthcare facilities.