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THERMAL INACTIVATION KINETICS FOR CALCULATING SPORE LONGEVITY.    Grant J. Boyadjian1, Wayne Nicholson2, Ph.D., and Patricia Fajardo-Cavazos2, Ph.D. 1Johns Hopkins University, Baltimore, MD 2University of Florida, Gainesville, FL / SLS Lab, Kennedy Space Center, FL

   Spore forming bacteria are the longest-lived cells known, have been isolated from ancient geological samples, and have been studied as candidates for interplanetary transfer by natural impacts and human spaceflight activities. In order to investigate extreme spore longevity, thermal inactivation kinetics were used to “speed up” the bacterial aging process.  Spores of Bacillus subtilis strain 168, suspended in either pure water or brine (saturated NaCl) were inactivated at various temperatures. Inactivation curves were plotted and D-values (decimal reduction values) calculated. The results revealed that spores suspended in brine exhibited increased longevity over spores suspended in pure water, suggesting that spores entrapped in hypersaline or evaporitic environments can potentially remain viable during the long periods of time often required by natural interplanetary transport.

(Supported by NASA's 2005 Spaceflight and Life Sciences Training Program.)   (Supported by NASA: SLSTP)