Action of Synthetic Polylysine on the Growth and Phagocytosis of Bacteria in Vitro

reviewed the biological properties of synthetic poly-a-amino acids. Katchalski, Bichowski-Slomnitzki, and Volcani, (1953) found that polylysine, polyarginine, and polyornithine had antibacterial action. Bichowsky-Slomnicki et al., (1956) synthesized a series of amino acid copoly-mers containing the amino acids in gramicidin S and found that basic residues were necessary for antibacterial activity and that lysine could be substituted for ornithine. Burger and Stah-mann (1952) earlier had studied the effect of synthetic lysine polypeptides on bacteria and found that growth was inhibited, the cells agglutinated, and respiration decreased. Polyly-sine was also found to inhibit various viruses and to increase the phagocytosis of starch par-ticles in vitro (Sela and Katchalski, 1959). The work described here is a study of the effect of polylysine on various pathogenic bacteria. MATERIALS AND METHODS Polylysine. Poly-L-lysine preparations were obtained from ammonia initiated polymerizations (Becker and Stahmann, 1952) in which molar ratios of anhydride to ammonia were 20, 40, 50, 160, and 240. One preparation was a poly-DL-lysine with 83 lysine residues. Another was ob-tained from a sodium methoxide initiated poly-merization with a ratio of anhydride to initiator of 320. Polylysine hydrochloride was dissolved in saline or distilled water, neutralized with sodium bicarbonate, and sterilized by filtration. Growth experiments. A defined or semidefined medium was used because polylysine combines readily with albumin and agar and gives pre-cipitates with nutrient broth, tryptose broth and serum. Davis minimal medium (Davis and