MICROBIOLOGICAL EXPERIMENT ON SPACE STATION ABOUT GENE EXPRESSION-1 AND 2
(MESSAGE-1 AND MESSAGE-2), TWO INVESTIGATIONS
Research Area: Microbiology
Expedition(s): 5, 7 and 8
Principal Investigator(s): ● Max Mergeay, DSc, Belgium Nuclear Research Center, Mol,
Belgium
● Natalie Leys, Belgium Nuclear Research Center, Boeretang,
Belgium
RESEARCH OBJECTIVES
The main objective of the Microbiological Experiment on Space Station About Gene Expression-
1 and 2 (MESSAGE-1 and MESSAGE-2) experiments is to study the effects of space conditions
aboard the International Space Station (ISS) on physiological and metabolic processes in
bacteria. Ralstonia metallidurans CH34 is a proteobacterium that can survive in harsh
environmental conditions. Rhodospirillum rubrum S1H (only used in MESSAGE-2) is of major
importance for a future bioregenerative life support system called MELiSSA under development
at the European Space Agency (ESA).
RESULTS
The results showed that space conditions can significantly change the physiology and metabolism
of bacteria. The differences in bacterial survival and growth observed between space and ground
cultures of R. metallidurans CH34 in the MESSAGE-1 experiment were not observed in MESSAGE-
- Also the R. rubrum S1H cell survival count indicated no significant difference between space
and ground-grown cultures. It should be noted that a more stable temperature control was
possible in the MESSAGE-2 experiment. The motility of R. metallidurans CH34 showed no
significant differences between ground and space cultures, though this was based on pure visual
analysis and did not allow good quantitative analysis. Flow cytometry data did not show any
significant difference between R. metallidurans CH34 cells grown in space or on ground for cells
size and shape, membrane integrity and potential, intracellular pH, and intracellular
concentrations of reactive oxygen species. For R. rubrum S1H, significant differences in cell
physiology were observed. Space-grown cells showed a change in cell size and shape in space
conditions. Cell permeability was increased and membrane potential was reduced under space
conditions, indicating a lower viability of cells grown in space conditions. The transcriptomic
analysis of R. rubrum S1H showed 372 genes that were significantly up-regulated under space
conditions. Typical genes related to oxidative stress were identified: H 2 O 2 detoxification, SOS
response (a global response to DNA damage in which the cell cycle is arrested and DNA repair and
mutagenesis are induced), iron transport, and metabolism. Induction of genes related to
chemotaxis, flagellum structure and metabolism, cobalamin metabolism, and nitrogen regulation
system were also observed.