Adsorption of phage P22 to Salmonella typhimurium

Adsorption of phage P22 to its receptor in the lipopolysaccharide (LPS) of the envelope of Salmonella typhimurium is accompanied by a hydrolytic cleavage of the O polysaccharide chain. The enzyme, and endorhamnosidase, is found in the phage tail. Propagation of a mutant of phage P22, containing two amber mutations, under restrictive conditions permitted isolation of phage tail parts with endorhamnosidase activity. The tail parts, purified by ion exchange chromatography, were shown to be homogenous by polyacrylamide gradient gel electrophoresis, isoelectric focusing in polyacrylamide gel electrophoresis and crossed immunoelectrophoresis. The mol. wt. was estimated to 240000. The optimal pH range for glycosidase activity was 5 to 7 and optimal temperature 37 degrees C. Hydrolysis of the O polysaccharide chain, when estimated with whole bacteria as the substrate, did not seem to be influenced by the cation concentration. Eclipse of P22 phage particles to whole bacteria was likewise uninfluenced by the cation concentration in the reaction mixture, but eclipse by isolated receptor containing LPS required cations. The optimal concentration for divalent cations was 2 X 10(-3) M, for trivalent cations 1 X 10(-3) M.