Abstract
We have made screening for antiphage antibiotics using an assay system of a malespecific filamentous phage, fl, and Escherichia coli as its host, and found a proteinous active substance named AFS (anti-filamentous phage substance) which was produced by an Actinomyces belonging to the group of Streptomyces lavendulae. It was purified from the filtered broth of the strain by ammonium sulfate precipitation and chromatographies of SP-Sephadex, CM-Sephadex and Sephadex G-50. The purified preparation was judged to be homogeneous by several column chromatographies and electrophoresis. Its molcular weight was about 5100 and isoelectric point was pH 9.9. Fourty two residues of amino acids, rich in the hydrophobic ones, were contained in one mole of AFS, but no carbohydrate was detected.
