The adsorption of bacteriophages by sensitive and resistant cells ofEscherichia colistrain B

Abstract

The adsorption isotherms of T2 and a tryptophan-requiring strain of T4 have been measured on Escherichia coli B and on mutant strains resistant to these bacteriophages. The susceptible host adsorbs the phages and each cell becomes saturated with approximately 300 particles of phage. L-Tryptophan is necessary for the adsorption of the T4 strain. The isotherms are of the general Langmuir type showing that phage adsorption is reversible, and it is concluded that the irreversible step of adsorption is suppressed in this system because of the occurrence of lysis from without. Resistant strains adsorb no bacteriophage at all, which shows that resistance is due to external exclusion of the bacterial virus. This type of resistance is compared with other types in which the agent has access to the cell and in which internal exclusion operates.