The Drying and Preservation of Bacterial Cultures

Abstract

A method is given which was found satisfactory for preserving dried cultures of some 1500 strains of bacteria. The organisms are suspended in nutrient broth in small cotton plugged tubes; frozen by immersion in a bath of glycerol and solid CO2 within a desiccator which is evacuated overnight; dry N2 is run in; the samples are redried under vacuum over P2O5 at room temp. for 7 days, after which dry N2 is admitted and the tubes sealed. Traces of moisture were found to be very deleterious, oxygen less so. The survival rate of such dried bacteria after heating at 80[degree] for 1 hr. was found to be a simple measure of the capacity of the particular batch to remain viable for extended periods of time under ordinary storage conditions.