Preservation of Microbiological Assay Organisms by Direct Freezing

Abstract

'rhe effects of freezinig on bacterial cultures have been investigated by numerous workers. The most commonly used method of preserving microorganisms is lvophilization (drying from the frozen state), but this is a drastic procedure for in most instances comparatively few organisms (2 to 3 per cent) survive the freeze drying process. Cultures preserved in this way have remained viable for as long as 35 years (Engley, 1956). However, the viability of the surviving organisms is low so that frequent serial transfers for 1 to 3 weeks are needed in order to reactivate the culture before use. It was felt that the adaptability, speed, and efficiency of microbiological assay procedures could be increased if a method of preservinig test organisms in a ready state could be developed.