PgmNr Y3020: NASA’s BioSentinel mission: using the power of yeast genetics in deep space.

Authors:
S. R. Santa Maria; D. Marina; S. Bhattacharya


Institutes
NASA Ames Research Center, Moffett Field, CA.


Keyword: Cell Cycle/Growth Control/Metabolism

Abstract:

Ionizing radiation presents a major challenge to human exploration and long-term residence in space. The deep-space radiation spectrum includes energetic particles that can generate a series of DNA lesions, including DNA double strand breaks (DSBs). DSBs represent a major disruption in the integrity of the genome, which can lead to cell death or the onset of carcinogenesis. DSBs can be repaired without errors via homologous recombination (HR), a conserved pathway in all eukaryotes from yeast to humans. While progress identifying and characterizing biological radiation effects using Earth-based facilities has been significant, no source duplicates the unique space radiation environment.

We are currently developing a biosensor-based nanosatellite to fly aboard NASA’s Exploration Mission 1 (EM-1) in 2018. Our biosensor uses S. cerevisiae to measure DSBs in response to ambient space radiation. The BioSentinel payload will contain a series of yeast strains, including: (1) a wild type strain as a control for yeast health and unrepairable DNA damage, (2) DNA repair defective strains that cannot repair DSBs and serve as radiation sensitive controls, and (3) a DSB BioSensor strain that can only grow in the presence of DSBs via heteroallelic HR repair. The BioSensor strain contains genetic defects that prevent growth until and unless a radiation-induced DSB near a reporter gene activates the yeast’s HR repair mechanisms. Thus, cell growth indicates a successful DSB-and-repair event. In BioSentinel, desiccated cells will be carried within microfluidic cards, and each card will be activated by medium addition at different time points over 18 months. Cell growth and metabolic activity will be tracked continuously via optical density. One reserve set will be activated only if a solar particle event (SPE) occurs during the mission. Biological measurements will be compared to data provided by onboard dosimeters and to Earth-based experiments.

BioSentinel will conduct the first study of biological response to space radiation outside Low Earth Orbit in over 40 years. BioSentinel will thus address strategic knowledge gaps related to the biological effects of space radiation and will provide an adaptable platform to perform human-relevant measurements in multiple space environments, including the International Space Station (ISS), on and around other planetary bodies, and other exploration platforms.