HR: 1330h
AN: B52B-1034    [PDF]
TI: Bugbuster: Survivability of Living Bacteria Upon Shock Compression
AU: * Willis, M J
EM: mjwillis@gps.caltech.edu
AF: California Institute of Technology, Seismological Laboratory (252-21), Pasadena, CA 91125 United States
AU: Ahrens, T J
EM: tja@gps.caltech.edu
AF: California Institute of Technology, Seismological Laboratory (252-21), Pasadena, CA 91125 United States
AU: Bertani, L E
EM: lebert@its.caltech.edu
AF: California Institute of Technology, Division of Biological Sciences (156-29), Pasadena, CA 91125 United States
AU: Nash, C Z
EM: nascz@gps.caltech.edu
AF: California Institute of Technology, Division of Geological and Planetary Sciences (170-25), Pasadena, CA 91125 United States
AB: Survivability of bacteria during impact events has implications both for the transport of life between planets and development of organisms on Hadean Earth and other planets during the period of heavy bombardment which ended 3.5 Gyr before the present [1]. We envision that life existed within internal rock surfaces immersed in the early ocean. We performed shock recovery experiments on live {\it E. coli} bacteria to determine survival rate vs. shock pressure. Samples of 2x10$^{7}$ cells were suspended in $\sim$10$^{-5}$ l of a buffer solution (TE: a 10:1 solution of Tris and EDTA), sealed into stainless steel chambers that are impacted by 1.5 mm thick flyer plates at 670-760 m s$^{-1}$ using a 20 mm gun. Recovered liquid was mixed with a nutrient broth (LB: growth medium containing tryptone, yeast extract and NaCl) and spread on a Petrie dish containing agar (a polysaccharide growth medium extracted from marine algae {\it Rhodophyceae}). Recovered samples were cultured for $\sim$16 hours at $37\deg$ C. In addition, sample bacteria studied under an optical microscope with DAPI fluorescent stain to verify presence of bacteria in shock recovered samples. Initial and reverberated shock pressures in H$_{2}$O varied from 0.2 to 2.0 and 2.4 to 14.9 GPa respectively. We modeled the bacteria cell walls with stilbene, $\rho$$_{0}$=1.16 g cm$^{-3}$, U$_{S}$=2.866+1.588u$_{P}$ and the cell interiors as water. Upon initial loading the net strain imposed on {\it E. coli} that just caused non-survival for 10$^{-6}$ s duration stress was 2.8. If this strain is characteristic of that tolerable by {\it E. coli}, we predict that shock stresses of 25 MPa, 25 kPa and 25 Pa are sustainable upon shock loading by 0.1 ms, 0.1 s and 100 s shock duration pulses. Such shock durations are induced by 2.5 m, 2.5 km and 2,500 km diameter silicate impactors. {\bf References:} [1] Maher K.A. \& Stevenson D.J., {\it Nature}, {\bf 331}, pp.612-614, 1988
DE: 0400 Biogeosciences
DE: 1630 Impact phenomena
DE: 3944 Shock wave experiments
SC: Biogeosciences [B]
MN: 2003 Fall Meeting