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Bugbuster — survivability of living bacteria upon shock compression

Willis, M. J. and Ahrens, T. J. and Bertani, L. E. and Nash, C. Z. (2006) Bugbuster — survivability of living bacteria upon shock compression. Earth and Planetary Science Letters, 247 (3-4). pp. 185-196. ISSN 0012-821X. doi:10.1016/j.epsl.2006.03.054.

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Shock recovery experiments were conducted on suspensions of 10^6/ml E. coli bacteria contained in a water-based medium that is emplaced within stainless steel containers. The water is shocked and recovered. These experiments simulate the environment of bacteria residing either in surface bodies of water or in subsurface water-filled cracks in rocks. Early Earth life is likely to have existed in such environments. However, the E. coli are not believed to be representative of early life and are merely used here for initial experiments. Some 10^(− 2) to 10^(− 4) of the bacteria population survived initial (800 ns duration) shock pressures in water of 220 and 260 MPa. TEM images of shock recovered bacteria indicate cell wall rupture and delamination. This appears to be the mortality mechanism. The TEM images indicate cell wall indentations may be occurring as would be consistent with Rayleigh–Taylor or Richtmyer–Meshkov fluid instabilities. In the present case, we consider the experiments as representing three layers of fluids: (1) The water-based medium, a stronger and possibly denser cell wall medium, and the interior of the cell cytoplasm. Variations of only 10–15% are expected in density. (2) A second mechanism that may cause cell wall failure is the multiple shock (nearly isentropic) compression freezing of liquid water medium into ice VI or ice VII high pressure phase that are 20% to 25% denser than the liquid. The decrease in volume associated with the transformation is expected to induce overpressures in the still liquid cell cytoplasm. Cell dynamic tensile wall strength thus appears to be a critical parameter from either of the above failure modes. Because the strain rate dependence of cell wall tensile strength is unstudied, we utilize the Grady and Lipkin [D.E. Grady, L. Lipkin, Criteria for impulsive rock fracture, Geophys. Res. Lett. 7 (1980) 255–258] model of tensile failure versus time scale (strain rate). Our single datum is fit to this law and we assume that at low strain rates, overpressures exceeding the cell Turgor pressure require on the order of ∼10^3 s. This model which has been applied to brittle media and metals for describing failure may permit application of short duration laboratory experiments as in the present ones to infer responses of organisms to much lower shock pressures, but for longer time scales (10^0 to 10^3 s) of planetary impacts. Using the present data for E. coli and applying the Grady and Lipkin model, we find that a 1.5 km diameter impactor will cause mortality of bacteria within a radius of 10^2 km but upon stress related attenuation the subsurface bacteria outside of this radius should survive.

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Additional Information:© 2006 Published by Elsevier B.V. Received 2 April 2005; received in revised form 31 March 2006; accepted 31 March 2006; Available online 16 June 2006. This research is supported by the National Aeronautics and Space Administration under Grant No. NNG04GI07G issued through NASA/Goddard Space Flight Center. We thank Editor Kenneth Farley for his encouragement and patience, reviewer, Rachel Maestra, an anonymous reviewer, for a series of helpful comments and suggestions, and Professor Carrine Blank. Professors Joseph Kirschvink and Dianne Newman also proffered comments and advice. Division of Geological and Planetary Sciences contribution #9089.
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Subject Keywords:bacteria; shock compression; origin of life; astrobiology
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Caltech Division of Geological and Planetary Sciences9089
Issue or Number:3-4
Record Number:CaltechAUTHORS:20141022-080700248
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Official Citation:M.J. Willis, T.J. Ahrens, L.E. Bertani, C.Z. Nash, Bugbuster—survivability of living bacteria upon shock compression, Earth and Planetary Science Letters, Volume 247, Issues 3–4, 30 July 2006, Pages 185-196, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50658
Deposited By: Tony Diaz
Deposited On:22 Oct 2014 16:42
Last Modified:10 Nov 2021 18:58

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