The rapid loss of viability ofAzotobacter in aqueous solutions

When a low number ofAzotobacter vinelandii 12837 log phase vegetative cells (2 × 10³ cells/ml) were removed from the culture liquid to water of the same temperature, a rapid loss of viability occurred depending on the procedure of washing and suspending. Death was not accompanied by visible lysis and the rate of loss of viability was less at lower temperatures, and in the presence of salts or cell-free filtrates from heavy cell suspensions in water. The die-off was erratic at increased cell concentrations and was accelerated by utilizable energy sources. Cells standing in a favorable ionic solution (0.1% NaCl) do not lose their viability while cells washed by a series of centrifugations with the same ionic solution show a progressive loss of viability with each washing. Phospholipids were found to leach from the cells into the aqueous solutions. Such cell death suggests instability of the cell membrane and the loss of osmotic or ionic control in the cells.This work was supported by grants AI-02830 and GM 600 from the U.S. Public Health Service.