LUX-in-Space - the long and stony way to Low Earth Orbit

Abstract

Experiments conducted in space are a rarity, making the opportunity to perform one on the International Space Station (ISS) exceptionally thrilling. However, apart from having a significant scientific query to address and a hypothesis that can only be tested in space, there are other essential elements required for success - dedication, patience, and resilience. The experiment known as LUX-ln-Space serves as an exemplary case study, highlighting the various stages involved in its preparation, the timeline, and its current progress. In space, all organisms are exposed to and affected by space radiation and microgravity. Radiation and microgravity were identified as two of the five most important hazards for manned spaceflight. Therefore, the knowledge of biological space radiation effects as well as the impact of microgravity on enzymatic repair processes is mandatory for risk assessment,especially in view of long duration missions to Mars or permanently inhabited bases on the Moon. The repair kinetics of radiation induced DNA damages will be investigated with the SOS-Lux Test. Bacteria serve as model organisms. They possess the same type of nucleotide excision repair as all other living organisms including humans. Salmonella enterica subsp. enterica cells are transformed with the pBR322-derived plasmid pPLS-1, carrying the promoterless lux operon of Photobacterium leiognathi as the reporter element controlled by a DNA damage-dependent SOS promoter as sensor element. In response to exposure to radiation the SOS promoter is activated. Due to the genetic modification, the connected socalled lux genes are expressed, resulting in the emission of measurable bioluminescence proportional to the applied dose of radiation. The DNA repair kinetics are followed by bioluminescence and optical density measurements. LUX-in-Space is the first space experiment where the whole series of events from DNA damage induction in metabolically active cells to the different steps of enzymatic repair will take place in real microgravity and the repair kinetics will be monitored in situ by optical measurements. The effects of microgravity will be clearly separated from other spaceflight factors by comparison with parallel samples on an onboard 1g centrifuge in the Biolab facility on the ISS and in a parallel ground control experiment with identical samples in flight-identical hardware.