Purified base-plate parts of bacteriophage P22 can bind to the host cell, Salmonella typhimurium. Although the reaction is reversible, a stable equilibrium is not formed between bound and unbound base-plate parts. This is because the binding sites on the cell, presumably the O antigens, are destroyed. The destruction of binding sites does not kill the cells, and, in fact, the binding sites are soon regenerated. The site-destroying activity reacts with P22 heads to make active phage and with antiserum made against purified phage. Therefore site-destroying activity is a characteristic of the base-plate parts and not some contaminant of the preparation.

Adsorption↗

PubMed1972

New deoxyribonuclease activity after bacteriophage P22 infection.

Extracts from P22-infected and uninfected cultures of Salmonella typhimurium were subjected to deoxyribonucleic acid (DNA)-cellulose and diethylaminoethyl-cellulose chromatography. Comparison of the elution patterns revealed that in infected cells there is a decrease in the amount of nuclease activity specific for denatured DNA and an increase in the amount of nuclease activity specific for native DNA. The latter activity was shown to differ from a similar host enzyme in Mg(2+), Mn(2+), and pH optima. This new activity is not found after infection of a lysogen with a nonvirulent phage or after infection under nonpermissive conditions with P22ts25.1 (a mutant in gene 25 that carries out no known functions other than adsorption and injection) and thus appears to be specified by the phage genome.

Ammonium Sulfate↗

PubMed1972

Inhibitory effect of bacteriophage P22 infection on host cell deoxyribonuclease activity.

Infection of Salmonella typhimurium with phage P22 causes a decrease in the activity of host deoxyribonuclease which degrades single-stranded deoxyribonucleic acid (DNA). This decrease is reversed when the infecting phage is P22c(+); it is not reversed if the infecting phage kills the cell. The decrease does not occur in infections with P22ts25.1 (which only adsorbs and injects DNA) or in infections of a lysogen by a nonvirulent phage. It does occur, however, after infections with other phages which are blocked in phage DNA synthesis. Inhibiting protein synthesis with chloramphenicol does not in itself cause the decrease in uninfected cells, but it does prevent infected cells from showing this effect.

Chloramphenicol↗

PubMed1972