Purified slime polysaccharide B and lipopolysaccharide of Pseudomonas aeruginosa strain BI were shown to possess receptor-like properties in inactivating Pseudomonas phage 2, whereas lipoprotein and glycopeptide fractions were devoid of activity. On a weight basis, slime polysaccharide B was more effective than lipopolysaccharide in inactivating phage. The specificity of the reaction with slime polysaccharide B was indicated by the fact that slime polysaccharide A of P. aeruginosa strain El failed to inactivate phage 2. Electron micrographs showed phage 2 in typical, tail-first position of attachment on intact cells of strain BI, slime polysaccharide B, and lipopolysaccharide. Tail fibers were discernible during phage attachment. The concept of specific phage receptor sites in the bacterial cell wall is well established. Inactivation of phages by isolated cell walls and purified receptor components of the cell wall has been

Phage 2 adsorbed to Pseudomonas aeruginosa strain BI in 5 mM Tris buffer, providing that cations like Na+, Mg2+, or Ca2+ were present. Adsorption was observed over a broad pH range, reaching a maximum level around pH 7.5, which coincided with the pH required for maximal activity of the phage 2-associated slime polysaccharide depolymerase. Mutants of strain BI and other strains of P. aeruginosa possessing slime layers that were devoid of phage 2 depolymerase substrate were incapable of adsorbing phage 2. On the other hand, those strains containing substrate for the phage 2 depolymerase in the slime layer were capable of adsorbing phage 2. The same relationship of phage depolymerase-substrate interaction to phage adsorption was observed with Pseudomonas phage 8, which possesses a depolymerase that differs in its specificity from the phage 2 depolymerase. The receptor-like activity of purified slime containing the specific substrate for the phage-associated depolymerase was demonstrable by its ability to inactivate phage. However, receptor-like activity or phage inactivation was not observed with those slimes that were devoid of the depolymerase substrate.