Abstract
Microorganisms perform countless tasks on Earth and they are expected to be essential for human space exploration. Despite the interest in the responses of bacteria to space conditions, the findings on the effects of microgravity have been contradictory, while the effects of Martian gravity are nearly unknown. We performed the ESA BioRock experiment on the International Space Station to study microbe-mineral interactions in microgravity, simulated Mars gravity and simulated Earth gravity, as well as in ground gravity controls, with three bacterial species: Sphingomonas desiccabilis, Bacillus subtilis, and Cupriavidus metallidurans. To our knowledge, this was the first experiment to study simulated Martian gravity on bacteria using a space platform. Here, we tested the hypothesis that different gravity regimens can influence the final cell concentrations achieved after a multi-week period in space. Despite the different sedimentation rates predicted, we found no significant differences in final cell counts and optical densities between the three gravity regimens on the ISS. This suggests that possible gravity-related effects on bacterial growth were overcome by the end of the experiment. The results indicate that microbial-supported bioproduction and life support systems can be effectively performed in space (e.g., Mars), as on Earth.
Highlights
Microorganisms such as bacteria are the foundation of Earth’s biosphere, including the human body, and will necessarily follow humans on their journey during space exploration
The samples launched to the International Space Station (ISS) were exposed to three different gravity regimens, while the reference experiment was conducted on Earth at 1 × g (Figure 2)
This is in contrast to the lack of significant difference observed for final cell counts
Summary
Microorganisms such as bacteria are the foundation of Earth’s biosphere, including the human body, and will necessarily follow humans on their journey during space exploration. Since they play many important roles in biological processes on Earth, they are expected to be essential in space. They have been shown to pervasively inhabit space stations such as the former Mir (Novikova, 2004) and the International Space Station (ISS) (Ichijo et al, 2016; Mora et al, 2019; Sielaff et al, 2019), with both negative effects and positive uses. In addition to being useful, they present challenges, e.g., through the formation of corrosive biofilms (Gu et al, 1998) and altered virulence in space (Wilson et al, 2007; Rosenzweig and Chopra, 2012)
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