Effect of Environmental and Physiological Conditions on the Phase of Adjustment of Pseudomonas fragi

The duration of the phase of adjustment of Pseudomonas fragi was affected by the physiological age and growth temperature of the inoculum, as well as by the temperature at which the growth curve was determined. Cultures in the exponential phase of growth gave shorter lags than stationary-phase and resting-phase inocula. Inocula from the latter phase gave the longest lags. Inocula grown at the temperature at which the growth curve was determined usually gave the shortest lags: the greater the difference between the incubation temperature of the inoculum and the incubation temperature of the growth curve, the longer the lag. Inocula grown at temperatures below the incubation temperature of the culture tended to produce longer lags than inocula grown at temperatures above the incubation temperature. The combined effect of physiological age and incubation temperature of the inoculum was additive. The effect of the incubation temperature of the culture upon the duration of the lag depended upon the method used to determine this phase. Lags that were measured in physical time (i.e., Lockhart's lag) decreased as the incubation temperature of the culture was increased, within the temperatures used. But Monod's lag, which measures physiological time, did not decrease as the temperature of growth increased but rather appeared to vary around some constant value dependent upon the physiological condition of the culture.