Binding of bacteriophage P22 tail parts to cells.

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.