Survival of Serratia marcescens in concentrates and suspensions stored at 5C.

From time to time, large volumes of bacteria may be required for purposes such as the isolation and identification of cellular components of metabolic products. Frequently a large quantity of one particular lot of cells is necessary so that enough replicates of an experiment may be performed to ensure a statistically valid result. For many reasons, replicate experiments may extend over considerable time, and therefore the stability of organisms becomes an important consideration in planning research problems. Reports on the survival of Serratia marcescens have been concerned either with the ability of stock cultures to yield viable subcultures after years of storage (Deacon, 1932) or with the quantitative recovery of dried cells (Rahn, 1945; Naylor and Smith, 1946). A search of the literature revealed no reports on the quantitative recovery of vegetative bacterial cells stored in an untreated condition. Such data on the quantitative recovery of S. marcescens stored as concentrates and as suspensions in several types of diluents were acquired as part of an experimental program not primarily concerned with storage of vegetative cells. The observations on the storage problems are presented to serve as a guide for those who have reason to store cells for experimental purposes and to stimulate the interest of other investigators in the problem.