The adsorption of phage to group N streptococci. The specificity of adsorption and the location of phage receptor substances in cell-wall and plasma-membrane fractions.

Abstract

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 0.1 to 1 p.f.u./coccus, the specificity of adsorption was similar to that of multiplication, but some strains also adsorbed one or more heterologous phages. At m.o.i. ≈ 100 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 30°. Three types of phage receptors, with different specificities, were recognized in the cell wall. Extraction of streptococci with lipid-solvents did not affect the adsorption of those phages which were irreversibly adsorbed to cell walls but reduced the adsorption 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.