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The E. coli mutant B/2, resistant to phages T 2 in free suspension, could be infected with T 2 using a „close packing“ technique. The experiments indicate that the first, electrostatic step of phage adsorption is dispensable and can be circumvented, the second, enzymatic step taking place immediately under conditions of forced contact between phage particle and resistant cell. Mutation to phage resistance in this case seems to have altered nothing but the electrostatic surface pattern of the bacterial cell wall.

Weak alkali extracts from the intact coli-B-cell a lipo-glycoproteid which after purification shows receptor activity against the phage T5 only. Purification of this material is described and data are given on physicochemical, chemical and functional properties of the T5 receptor substance as well as of receptor-inactive material extracted from B/1,5. From all the data available it is tried to form a picture of the entire structure of the coli cell wall and to connect it with the phage infection mechanism.

In an attempt to gain more in-vitro-knowledge on the process of adsorption between bacteriophage and susceptible host cells, empty cell membranes of E. coli B have been prepared by enzymatic digestion procedures and exposed to the phages of the T-series. It was found, that T 2, T 4 and T 6 are adsorbed specifically by isolated membranes. The kinetics of adsorption on membranes resemble in every detail those obtained with living bacteria. Electron micrographs and observations with the phase contrast microscope give strong evidence of drastic alterations occurring to both phage particle (T 2) and membrane on which it is adsorbed. Enzymatic activities on the part of the phage paralleling those encountered with viruses of the Mumps-NDV-Influenza Group may be involved. But the process of adsorption becomes irreversible with T 2 and membranes. It is hoped to have a system at hand allowing further study under simplified conditions of the mechanism of penetration of certain types of phages through the intact cell wall of their host.

Quantitative precipitin tests indicate the absence of serological differences between the receptor substance for the bacteriophage T5 and its inactive analog from B/1,5. The implications of this result are discussed.

Highly purified T 5-receptor substance was irradiated with X-rays, and a one-hit dose response was obtained. By comparing quantitatively the results of two independent tests, both of which measure “survival“ of receptor after irradiation, it was possible to conclude that the receptor-active site of one receptor particle must be larger than the cross-section of a T 5-phage tail. However, since receptor particles were never definitely observed to have combined with more than one T 5-particle, secondary processes must be involved in the binding reaction, leading to a rapid inactivation of any surplus receptor-active areas on the receptor particle undergoing the reaction.

Receptor-triggered DNA-ejection of T5-phage is made directly visible. The DNA leaves the phage particle through its tail and emerges from the narrow gap between tailtip and receptor particle, appearing as a single thread of 34 ± 1.7 u length, equivalent to a molecular weight of 66 x 106.

It is shown that attachment of the T5 tailtip to its specific receptor requires an activation energy of 11 kcal/M and is irreversible. It is this reaction which, probably through formation of covalent bonds between phage and receptor, causes inactivation of the phage particle. The subsequent ejection of its DNA is merely accessory in this respect. In contrast, the bonds between phage T1 and its specific receptor are easily dissociable, the phage is released intact, and the binding requires an activation energy of only 4 kcal/M.

Dissociation in 90% phenol uncovers a layer of the Coli B-cell membrane showing the typical antiviral specificity of the receptor for phages T3, T4 and T7. Chemical analysis proved glucose, glucosamine and a yet unknown carbohydrate, probably a heptose, to be components of the receptor material, which amounts to about 13% of the dry weight of the whole membrane.