Free-Radical Formation during Storage of Freeze-dried Serratia marcescens

Abstract

BACTERIA which have survived freeze-drying retain the capacity to regenerate colonies after prolonged storage under vacuum, in contrast to their rapid loss of this capacity when stored in air. The question of whether bacteria stored under such conditions are dormant or whether some metabolic activity continues to maintain the bacilli in a living state is of fundamental importance to a further understanding of the physiology of life in low-moisture environments. Heckly¹ has reviewed many of the problems associated with freeze-drying. Results of preliminary work on freeze-dried cells had indicated a slow gaseous uptake when the material was stored in dry air and a greater uptake if stored under moistened air. Because the results were not reproducible, other techniques were examined, specifically that of electron paramagnetic resonance, in the hope of finding an indirect measurement of respiration. The fundamental theory and practice of electron paramagnetic resonance has been reviewed by Ingram², while a review of biological applications of the phenomenon has been given by Sands³.