Magnetotactic bacteria (MTB) biomineralize intracellular, nano-sized magnetic mineral crystals of magnetite (Fe₃O₄) and/or greigite (Fe₃S₄), termed magnetosomes. As one of the most complex prokaryotic organelles, magnetosomes conduct functions in magnetotaxis and potential detoxification. Moreover, the high density of magnetosomes leads to a hypothesis regarding their potential roles in gravity sensing (Urban, 2000). Microgravity represents a pivotal environmental stressor in space, exerting significant effects on microbial growth dynamics and physiological metabolism (Bijlani et al., 2021). Despite the pioneering study of Urban (Urban, 2000), our understanding of the effects of microgravity on MTB remains very limited. Here, we conducted an exposure experiment simulating microgravity condition using a Random Positioning Machine (RPM) on Magnetospirillum gryphiswaldense strain MSR-1 (MSR-1). We find that MSR-1 cultures grown under simulated microgravity exhibited a marked reduction in magnetosome synthesis, with smaller average size and more superparamagnetic particles. Five key magnetosome genes was significantly downregulated (FoldChange < -2, q < 0.05) which are potentially contributing directly to the impaired magnetosome synthesis observed under simulate microgravity. And the KEGG pathway enrichment analysis suggested that chemotaxis pathways were enriched in the microgravity group. Results of this research will improve our understanding of the effects of extraterrestrial microgravity environments on microbial biomineralization and biogenic nanomaterials synthesis.

References
Bijlani S, Stephens E, Singh N K, Venkateswaran K., Wang C.C.C., Advances in space microbiology. iScience, 24 (2021) 102395.
Urban J. E., Adverse effects of microgravity on the magnetotactic bacterium Magnetospirillum magnetotacticum. Acta Astronaut, 47 (2000) 775-780.
 

Magnetotactic bacteria,Simulate microgravity,Biomineralization,Space microbiology