Long-term multi-generational evolutionary studies of bacteria in the spaceflight environment — Abstract: Understanding how organisms adapt to the spaceflight environment is an essential component of future space exploration, and informs how life co-evolves with unique environments. Microbes will play fundamental roles in the development of biologically-based closed-loop regenerative life support, in-situ resource utilization, and will have extensive interactions with human and plant hosts. Further, microbes will pose challenges through disease and contamination, e.g., as nuisance factors such as biofilms in water supply, ventilation systems, as well as through growth in condensates and on surfaces. Understanding adaptive evolution of microbes to space and spaceflight will also deepen our understanding of the limits of life and of habitability. Previous spaceflight experiments with microbes have documented striking physiological and phenotypic changes in response to microgravity in the spaceflight environment including differences in growth rates, enhanced antibiotic resistance and virulence, and mutation of specific phenotypic traits. However, understanding the underlying evolutionary process at the molecular level presents a unique challenge due to the requirements for long-term multi-generational studies.
By developing methods for continuous growth and selection on cells, and approaches that allow us to accelerate the natural rates of de novo evolution with mutator phenotypes and native competence for DNA-uptake, we can maximize the number of generations grown within the constraints of hardware currently available onboard the International Space Station. Using the model organism Bacillus subtilis 168, these methods will allow us to test hypotheses regarding the rates and nature of adaptive evolutionary change and fitness in microbes in response to microgravity and spaceflight conditions, compared to 1-g and ground controls.