Biological Activity and Mode of Action of a Specific Antiphage Substance,AFS

Purified AFS (anti-filamentous phage substance) produced by Streptomyces lavendulae AM–7a showed specific antiphage activity against the male specific, deoxyribonucleic acid-containing filamentous phages of Escherichia coli without any activity against other DNA-phages nor the male-specific ribonucleic acid-containing phages of E. coli. AFS brought about no inactivation of free particles of filamentous phage, fl, nor the receptor of the host cells for the phage, while it showed strong killing effect against the fl-infected host cells at the concentration below 0.01 μg/ml. Antiphage activity of AFS might be due to its highly specific killing effect only on the E. coli cells infected with the filamentous DNA phages, while it exerted no effect on the growth of the unifected E. coli nor other microorganisms. Killing by AFS seemed to require the energy metabolism of the phage-infected host cells. Macro-molecular synthesis and respiration of the infected host cells were inhibited soon after the addition of small amounts of AFS without any cell lysis.