Using Electron Paramagnetic Resonance Spectroscopy to Determine the Role of Free‐Radical Protection in Tardigrade Survival Mechanisms
Authors: Crislip Jessica Ray , Smythers Amanda , Kolling Derrick Richard 
Published: April 2020

As aeronautic technology advances, so does the possibility of long‐term space travel and exploration. However, in order to make significant strides, it is first necessary to determine how to survive the antagonistic space environment, including temperature extremes, UVC radiation, and vacuum pressures, among others. Tardigrades are microscopic invertebrates that possess the ability to adapt to extreme environments through the formation of a tun, a dormant structure resulting from the downregulation of metabolism. This ability to survive under extreme conditions, including arctic temperatures, extreme heat, and a pure vacuum, makes tardigrades a useful model organism for space survival. By increasing our understanding of their survival mechanisms on a fundamental level, we may be able to generate technologies that protect humans in space from diseases caused by ROS and the damaging effects of oxidative stress.

Previous research has examined the physiological response of tardigrades subjected to freezes and irradiation that model outer Earth conditions. In these studies, tardigrades were shown to enter tun formation through cryptobiosis, especially in response to physical stressors causing desiccation. Another study assessed tardigrades’ intergalactic survival capability by sending a culture into the vacuum of space, after which the cultures showed no loss of viability. We hypothesize that tardigrades have a specific, protective mechanism to respond to oxidative stress through the increased expression of superoxide dismutases (SODs) to break down potentially harmful ROS, which is supported by previous studies showing both the formation of superoxide radicals as well as an increase in SODs in desiccated animals.

In this study, X‐band continuous wave electron paramagnetic resonance (EPR) spectroscopy was used to measure the presence of superoxide radicals in the tardigrade Hypsibius exemplaris before and after exposure to environmental stressors. Tardigrades were subjected to a combination of UVA and UVB irradiation before the addition of a spin probe, and the resulting EPR spectrum was compared to a nonirradiated H. exemplaris control. Results show that the tardigrades generated less ROS following environmental stress exposure, supporting the hypothesis of a protective mechanism to mediate radical production when subject to harsh conditions. Studies concerning other physical and chemical stressors, as well as examining radical production in tardigrades upon inducing tun formation, are ongoing. Further experiments also include determining specific activities of proteinaceous antioxidants like SOD before and after these exposures.

Support or Funding Information

J.R.C was supported the SURE Program funded through the West Virginia Research Challenge Fund, and administered by the West Virginia HEPC, DSR, Award Number DSR.17.09,the WV NASA Space Grant Consortium's NASA WV Space Grant Undergraduate Fellowship Program and from a Marshall University Creative Discover & Undergraduate Research Award.

D.R.J.K. and A.L.S. were supported by the National Science Foundation under Cooperative Agreement No. OIA‐1458952.