Methods for Increasing Survivability During Storage of Exponentially Growing Bacteria

Abstract.

A protocol has been developed for storing Gram (−) bacterial cells at 0°C, which allows greater than 90% of stored cells to retain colony-forming ability for up to 60 days. The protocol, which yields essentially identical results when used with Escherichia coli or Pseudomonas aeruginosa, does not enhance survivability of Bacillus cereus. The greatest and longest survival is enjoyed when exponentially growing cells in minimal-glucose medium are deprived of carbon for about 9 h, supplemented with 750 μg/ml chloramphenicol, and immediately placed at 0°C. By decreasing the period of carbon starvation from 9 to 5 h, or increasing the period of carbon starvation from 9 to 12 h, both the ultimate survival rate and kinetics of loss of culturability are affected. Survival enhancement induced by chloramphenicol is not similarly induced by kanamycin.