Lysin production by phi C2(W), a prolate phage for Streptococcus lactis C2.

A bacteriophage, phi C2(W), which attacked Streptococcus lactis strains C2, ML3 and 712, is described. It had a prolate head and non-contractile tail and produced large haloes around plaques. Infection of eight paired-strain cultures, each containing Str. lactis C2, with phi C2(W) resulted in marked inhibition of acid production for six cultures. Direct phage-nonhomologous "host' contact was not required for inhibition. Lysates of phi C2(W) contained a phage-induced lysin. Evidence is presented that the inhibitory effect of phi C2(W) against paired and multi-strain cultures is due to the lysis of phage-insensitive strains by phage lysin. An isometric phage, phi 712, was shown not to produce such a lysin.