Mode of action of bacteriophage phi 149 on cholera and El Tor vibrios.

Bacteriophage phi 149 which was propagated in Vibrio cholerae (classical) OGAWA 154 strain, killed Vibrio cholerae (El Tor) strain MAK 757 without phage propagation. El Tor vibrios underwent a small degree of lysis only when infected by the phage phi 149 at a high multiplicity of infection and lost their viability at a rate-dependent multiplicity of phage infection. Evidence was obtained with 32P-labelled bacteriophage phi 149 for penetration of phage DNA into both bacterial strains. In host strain (OGAWA 154) phage particle synthesis occurred normally. In El Tor strain MAK 757 the phage DNA was not degraded but its expression was blocked. The killing effect of phi 149 on El Tor strain MAK 757 is supposed to be due to damage of the cytoplasmic membrane, which could not be repaired under the influence of phage information. This was indicated by a blockage of cellular respiration and RNA and protein synthesis.