Microbial virulence and resistance in low-shear environments/microgravity

 

Space travel, and potential colonization are an important part of NASA's agenda. Yet, how bacteria might behave under conditions of diminished gravity has been little studied. We are studying bacteria grown in microgravity, using specially designed reactors. Bacteria acquire increased virulence and resistance during such growth. These characteristics resemble the general stress response of bacteria under normal gravity conditions. However, the molecular mechanisms of the two phenomena are radically different. Since human immune system becomes weakened in low gravity, the increased bacterial virulence and resistance are of concern for space travel and habitation. Our attempts to determine the molecular basis of this response should identify targets to address this problem. Our recent findings show that microgravity drastically alters regulatory processes that are influenced by folding patterns of macromolecules. Whether microgravity influences folding patterns is now being directly investigated.

Low-shear environments are encountered by pathogens on Earth and these studies are thus relevant to combating diseases on Earth.

Recently, we grew E. Coli biofilms under simulated microgravity conditions; they were more resistant than normal gravity biofilms of this bacterium, further underscoring the potential danger posed by microbes in space exploration. Mathematical analysis confirms that low-shear/microgravity conditions are generated for the biofilms growing in these HARVs. See Biofilm section for further details.

 

Biofilms on microcarrier beads (top right images), and respective high resolution rendering of Z-stacks from 24 h normal gravity (A) and simulated microgravity (B) biofilms, demonstrating increased coverage under the latter conditions.

Lynch, S.V., K. Mukundakrishnan, P. Ayyaswami, and A. Matin. 2006. Escherichia coli biofilms formed under low shear simulated microgravity in a ground-based system. Applied & Environmental Microbiology 72 (12): 7701-7710 [PDF]

Matin, A., and S. Lynch, and M. R. Benoit. 2006. Increased bacterial resistance and virulence in simulated microgravity and its molecular basis. Gravitation and Space Biology 19(2): 31-42 [PDF]

Lynch, S.V., E.L. Bradie, and A. Matin. 2004. Role and regulation of sigmaS in low shear microgravity-conferred general resistance in Escherichia coli. Journal of Bacteriology 186(24): 8207-8212 [PDF]

Matin A., and S.V. Lynch. 2005. Investigating the Threat of Bacteria Grown in Space. ASM News 71(5): 235-240 [PDF]

Lynch S.V. and A. Matin. 2005. Travails of microgravity:man and microbes in space. Biologist 52(2): 80-87 [PDF]

The Synthecon bioreactor for growing cells in microgravity.