The effect of temperature on lysis of cells and cell walls of Bacillus psychrophilus

Cells of Bacillus psychrophilus lysed rapidly when suspended in carbonate or phosphate buffer at a temperature above the maximum growth temperature (30C). This lysis was found to be temperature dependent. The effect of various inhibitors of whole cell lysis was examined. D-Serine, CaCl2, sucrose, and polyethylene glycol were found to be quite effective in inhibiting lysis at 37C. However, this inhibition seemed to be nonspecific. Lysis of isolated cell walls of this psychrophile was also found to be temperature dependent. Lysis was linear and zero order throughout the growth range of this organism. However, as the temperature was increased (37 and 45C) the rate of lysis increased rapidly and zero-order kinetics was lost at these elevated temperatures. D-Aspartic acid was the most effective inhibitor of cell wall lysis. However, its action was only apparent at temperatures above the maximum growth temperature. These results suggest that the cell wall of B. psychrophilus is unusually heat labile and indicate a novel mechanism of lysis.