The Role of Calcium in the Penetration of Bacteriophage T5 Into Its Host

Certain peculiarities of the early phases of in-fection of Eseheichia coli, strain B, with phage T5 were observed by Lanni (1954). Separation of phage desoxyribonucleic acid from phage protein and penetration of desoxyribonucleic acid into the host cell, as observed with phage T2 (Hershey and Chase, 1952), do occur under the conditions of a one-step growth experiment, but fail to take place if the cells are infected and kept in nutrient broth at high bacterial concentrations (over 2 X 109 cells per ml). Like many other phages, T5 re-quires calcium (or magnesium, or strontium) ions for growth (Adams, 1949; Kay, 1952). Calcium deficiency arrests phage development at an early stage following adsorption. The obvious guess, that calcium is required for the penetration of the phage desoxyribonucleic acid, was verified by ex-periments reported here. MATERIALS A " METHODS E. coli, strain B, phage T5, and the routine methods in phage experiments were employed (Adams, 1948a). Adsorption generally was car-ried out with bacteria from young cultures con-centrated to a density of 2 to 8 X 109 per ml. It was over 95 per cent complete in four minutes. The basal synthetic medium used (Kay, 1952)