SUMMARY

The specificities of adsorption and multiplication of phages attacking some strains of lactic streptococci (serological group N) were investigated. At multiplicities of infection (m.o.i.) of o. I to I p.f.u./coccus, the specificity of adsorption was similar to that of multiplication, but some strains also ad-sorbed one or more h¢terotogous phages. At m.o.i. ~ IOO both homologous and heterologous strains of streptococci were lysed from without. The specificity of adsorption to cell walls was the same as to whole cocci and, with the exception of 2 phages, was irreversible at 3o °. Three types of phage receptors, with different specificities, were recognized in the cell wall. Extrac-tion of streptococci with lipid-solvents did not affect he adsorption of those phages which were irreversibly adsorbed to cell walls but reduced the adsorp-tion of other phages. The plasma membrane of Streptococcus lactis strain ML 3, but not the cell wall, inactivated phage ml 3 but not heterologous phages in the presence of electrolytes. The plasma membrane of a phage-resistant mutant of this strain did not inactivate phage although it was similar in chemical composition to that of the parent strain