CHARACTERISTICS OF A FACTOR PROTECTING THE VIABILITY OF LYOPHILIZED BRUCELLA ABORTUS CELLS'

The ability of some microorganisms to survive a stress treatment such as freeze drying has been shown to improve when aging the cells is done before drying. Hutton and Shirey (1951) de-scribed the beneficial effects of adding filtrates from aged cultures to cell paste of Brucella abortus before freeze drying. Record and Taylor (1953) showed that an exudate of Escherichia coli offered protection to Escherichia coli and to other organ-isms as well. These investigators have suggested that this biological activity is due to a substance from bacteria and that it is effective in relatively small concentrations. We have studied the action of this viability protective factor (VPF) and have separated it from other constituents of the bacterial exudate. Also it has been partially characterized. The work reported here concerns the extraction of VPF from Brucella abortus and the measurement of its activity upon the survival of this organism during freeze drying. MATERIALS AND METHODS The culture employed was Brucella abortus BAI strain A-19 grown in a tryptose-cerelose broth at 32 C. This medium had the following composition in g/L: tryptose (Difco), 20.0; cere-lose, 10.0; NaCl, 5.0; and 10 ml of a Seitz filtered solution containing 25 mg of thiamin hydrochlo-ride (per L) which was added aseptically after the other ingredients had been autoclaved. Two per cent agar was added when a solid medium was desired. In order to obtain cell paste for the production 1 The major portion of this investigation wa