The Influence of Temperature and Nutrients on Plaque Formation by Bacteriophages Active on Escherichia coli Strain B

Abstract

At 15 C, E. coli strain B, grown on an ammonium lactate agar (F), becomes resistant to some of the viruses to which it is sensitive at 37 C. These effects were not noted with strain B grown on complete nutrient (N) agar. In all cases tested the efficiency of plaque formation by the virus T4 on F agar at - 15 C was brought to unity by addition to F agar of 20 [gamma] per ml. of l-tryptophan, an adsorption cofactor T4. A consideration of these and previous results suggests that the metabolism of the bacteria in minimal medium furnishes sufficient cofactor for the activation and adsorption of those strains of T4 that are efficient in forming plaques on F at 37 C, but that these amts. of cofactor in many cases are not sufficient at 15 C. A survey of the other viruses of the T set disclosed similar inefficiencies at 15 C in the formation of plaques by our stocks of T1 and T7. These deficiencies were at least partially overcome by the addition of certain amino acids to the F agar. The possibility that resistance and sensitivity of host cells are at least in part detd. by their metabolism is discussed in the light of these results.