Phage Specificity

A deoxyribonuclease not normally present in E. coli is rapidly synthesized after infection with phage T5 (47). This DNase appears at approximately the same time as the other early phage-specific enzymes (DNA polymerase and deoxynucleotide kinase, etc.) induced following infection with this bacteriophage. 

The polysialic acid capsule of E. coli K1 is not only an essential virulence factor it also provides an attachment site for specialized K1 bacteriophages. Almost 30 lytic enterobacterial phages specific for E. coli K1 have been isolated, mainly from sewage samples. Interestingly, they have been found to exhibit different morphologies, thus belonging to the three different families of the Caudovirales (Table 1). 

Mycobacteriophage D4 is a phage specific for M. smegmatis and its adsorption onto cells of M. smegmatis can be inhibited by compounds... 

These morphogenetic problems consist essentially of regulation of the temporal sequence of synthesis of phage-specific proteins and formation of each protein in the amounts necessary for phage reproduction. In this case coat proteins or protein are formed in much larger amounts than enzyme proteins, both early (RNA-synthetase) and late (lysozyme). 

Synthesis of phage-specific RNA in the case of phage 0X174 evidently takes place under the influence of DNA-dependent RNA-polymerase. No repressor of synthesis of host RNA and DNA appears at the beginning of infection, for this synthesis continues parallel to phage formation, almost until the phase of lysis (Rueckert and Zillig, 1962). 

The existence of phage-induced inhibitors of DNA-dependent RNA-polymerase has also been demonstrated by more direct methods (Khesin, Shemyakin,etal, 1962 Skold and Buchanan, 1964). In phage A which contains a somewhat smaller DNA than the phages of the T group, differences between the nucleotide composition of phage-specific messenger RNA molecules formed in the early and late periods of phage reproduction have been clearly demonstrated (Skalka, 1966). 

Since synthesis of every protein is preceded by the formation of a specific template on DNA, in the form of molecules of messenger RNA reproducing the nucleotide code of the structural cistron of the particular protein, it is obvious that successive synthesis of different phage-specific proteins over a period of time implies that... 

Weiss and co-workers (1968) have showoi by the method of RNA/DNA hybridization that part of the leucyl and prolyl sRNA formed in E. coli cells after Infection with phage T4 is phage-specific. It may thus be assumed that these phages have genes for the synthesis of a number of phage-specific transfer RNA molecules which are the factors switching cell synthesis over to phage reproduction. 

Fig. 15. RNA-phage infection of a bacterial cell as a simple hyper-cyclic process. Using the translation machinery (T) of the host cell the infectious plus strand (I ) first instructs the synthesis of a protein subunit which associates with three host proteins to form a phage-specific RNA-replicase. This replicase complex (R) exclusively recognizes both phage-RNA strands, plus and minus, and replicates them.

The conversion of macromolecular syntheses of the host to phage specificity is a complicated but systematic process ... 

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