Bacteria misbehaving in space

ILLU_0432_Microbial_EscherichiaColi

Tougher and more virulent?

Human biology presents numerous limitations when it comes to space travel. Bacteria are more adaptable, robust and resilient, and are known to thrive in even the most extreme environments. But how do they fare in space? To date, numerous bacterial experiments have been conducted in Earth’s orbit. We know that bacteria grown in space exhibit a number of differences relative to their behavior on Earth.

What are the observed differences? A reduced lag phase and increased final population density have been consistently reported for non-motile, suspension cultures (1). Improved biofilm formation (2-3), higher specific productivity of secondary metabolites (4), a thicker cellular envelope (5) and enhanced conjugation efficiency (6) have also all been documented. Aside from these altered growth characteristics, there have also been reports of increased virulence (7–8) and a reduced susceptibility to antibiotics (9–15). Radiation worries aside, these findings are clearly alarming for crew on manned missions, for example on the International Space Station, as these health-related findings present new challenges when it comes to treatment of potential infections. The key question is what are the underlying molecular mechanisms responsible for the “strange” behavior exhibited by bacterial cells in space?

Microgravity is to blame. Changes in bacterial behavior are thought to be due to reduced mass transport in the local extracellular environment. In the absence of gravity-dependent convection, movement of molecules consumed and excreted by the cell is limited to diffusion. In order to test this hypothesis, a new study by Zea et al. evaluated differential gene expression in E. coli suspension cultures grown in space and on Earth (16). The team extracted RNA using QIAGEN’s RNeasy Mini Kit for use in RNA-seq library preparation, and performed data analysis with QIAGEN’s CLC Genomics Workbench. They aimed to demonstrate an overexpression of genes linked to a reduction in extracellular mass transport. These included genes associated with starvation and the utilization of alternative energy sources, increases in metabolism, enhancement of acetate production and other systematic responses to acidity. The team’s gene expression data confirmed that reduced extracellular mass transport is the primary underlying gravity-dependent, physical mechanism responsible, at least in part, for the altered behavior that bacteria typically exhibit in space (16).

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References

  1. 1. Horneck, G., Klaus, D.M., and Mancinelli, R.L. (2010) Space microbiology. Microbio. Molec. Bio. Rev. 74, 121.
  2. 2. Kim, W. et al. Spaceflight promotes biofilm formation by Pseudomonas aeruginosa. PloS One 8, 4.
  3. 3. McLean, R.J.C., Cassanto, J.M., Barnes, M.B., and Koo, J.H. (2013) Bacterial biofilm formation under microgravity conditions. FEMS Microbio. Let. 195, 115.
  4. 4. Benoit M. R. et al. (2006) Microbial antibiotic production aboard the International Space Station. Appl. Microbio. Biotechnol. 70, 403.
  5. 5. Tixador, R. et al. (1985) Preliminary results of cytos 2 experiment. Acta Astro. 12, 131.
  6. 6. Ciferri, O., Tiboni, O., Di Pasquale, G., Orlandoni, A.M., and Marchesi, M.L. (1986) Effects of microgravity on genetic recombination in Escherichia coli. Naturwissensch. 73, 418.
  7. 7. Crabbé A. et al. (2011) Transcriptional and proteomic responses of Pseudomonas aeruginosa PAO1 to spaceflight conditions involve Hfq regulation and reveal a role for oxygen. App. Env. Microbio. 77, 1221.
  8. 8. Wilson, J.W. et al. (2007) Space flight alters bacterial gene expression and virulence and reveals a role for global regulator Hfq. Proc. Natl Acad. Sci. 104, 16299. doi: 10.1073/pnas.0707155104. pmid:17901201
  9. 9. Ricco, A.J. et al. (2010) PharmaSat: drug dose dependence results from an autonomous microsystem-based small satellite in low Earth orbit. Tech. Dig. Solid-State Sens. Act. Microsys. Workshop, 110.
    10. Kitts, C. et al. (2009) Initial flight results from the PharmaSat biological microsatellite mission. Proc. 23rd Ann. AIAA/USU Conf. Small Sat., Logan UT.
  10. 11. Parra, M., Ricco A.J., Yost, B., McGinnis, M.R., and Hines, J.W. (2008) Studying space effects on microorganisms autonomously: genesat, pharmasat and the future of bionanosatellites. Gravit. Space Bio. 21, 9.
    12. Tixador, R. et al. (1994) Behavior of bacteria and antibiotics under space conditions. Aviat. Space Env. Med. 65, 551.
    13. Lapchine, L., Moatti N., Gasset, G., Richoilley, G., Templier, J., and Tixador, R. (1986) Antibiotic activity in space. Drugs under Exp. Clinic. Res. 12, 933.
  11. 14. Moatti, N., Lapchine, L., Gasset, G., Richoilley, G., Templier, J., and Tixador, R. (1986) Preliminary results of the “Antibio” experiment. Naturwissensch. 73, 413.
  12. 15. Tixador, R. et al. (1985) Study of minimal inhibitory concentration of antibiotics on bacteria cultivated in vitro in space (Cytos 2 experiment). Aviat. Space Env. Med. 56, 748.
  13. 16. Zea, L. et al. (2016) A molecular genetic basis explaining altered bacterial behavior in Space. PLoS ONE 11, e0164359. doi:10.1371/journal.pone.0164359
Devika Mathur

Devika Mathur is a Senior Technical & Marketing Writer at QIAGEN. Devika joined QIAGEN in 2008 and has been responsible for creating literature for numerous QIAGEN products, including the REPLI-g and QIAseq product lines, and has written extensively on various scientific topics ranging from next-generation sequencing and single cell analysis to PCR and sample preparation. Devika is a graduate from University College Cork, Ireland, and has a microbiology research background, focusing primarily on the molecular characterization of the replication module of the lactococcal bacteriophage Tuc2009.

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