The Preservation of Bacterial Cultures. I

Abstract

The maintenance of a large collection of stock cultures of bacteria for ready availability is a major task. The method of frequent transfer on a suitable culture medium, as commonly employed, requires not only a great expenditure of time, materials and effort, but also involves the possible loss of certain biological, immunological and cultural characteristics; not to mention the occasional loss of the strain through such agencies as contamination , drying of the medium and contact with accumulating metab-olites. It is the purpose of this paper to present (a) a review of the literature on the preservation of bacteria, (b) a comparison of three of the methods commonly employed for preserving bacterial cultures and (c) an emphasis on an inexpensive and practical method for preserving such cultures as are required to be available at all times for frequent subcultures. To preserve cultures, and at the same time to maintain them in as nearly as possible their original state, various technics have been advocated. All, however, appear to be based upon one of two principles: First, the prevention of slow-drying of the cultures , or, second, the use of rapid desiccation. A review of the literature has revealed that most of the methods of preservation have been tried only on a limited number of bacterial species; practically none have been subjected to critical study. It is difficult to determine, therefore, whether they would be applicable to a large and varied stock culture collection. It is our object to evaluate three representative methods by testing them against most of the species commonly maintained 163