Summary. During early exponential growth of Escherichia coli in the absence of phenol there is a natural death rate at 20, 30, and 44° but at the optimum temperature around 37° there is little if any significant death. The influence of a rise in temperature from 20 to 44° is to decrease the generation time and at 44° the lower generation time compensates for a reduced generation index. The main effect of sub‐bacteriostatic concentrations of phenol is to increase the generation time but at 30, 37 and 44° there is a significant reduction in the generation index at the higher concentrations resulting in a dynamic bacteriostasis. At 20° bacteriostasis is due mainly to a large generation time but there is a little growth and so bacteriostasis is essentially dynamic. There is also evidence to suggest that the effect of a particular concentration of phenol on the generation index is not merely influenced by the temperature but by the generation time under the particular set of conditions. If phenol is added to rapidly growing cultures of E. coli the effect of a rise in temperature is to reduce the concentration required for bacteriostasis but if it is added during the lag phase there is a maximum in the bacteriostatic concentration between 20 and 37°.
SUMMARY: Different suspensions of Bacterium coli in distilled water, prepared by a routine technique and adjusted nephelometrically with reference to a ground glass screen, showed no significant difference in their viable counts at the 5% level.
In a study of the inhibition by phenol of cultures grown in peptone water from inocula of such suspensions the regression line obtained by plotting the probit of the percentage inhibition against the logarithm of the concentration was rectilinear. From this the concentration needed for 95% inhibition was calculated.
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