Requirement for calcium ions in mycobacteriophage I3 DNA injection and propagation

Ca²⁺ ions are absolutely necessary for the propagation of mycobacteriophage I3 in synthetic medium. These ions are required for successful infection of the host and during the entire span of the intracellular development of the phage. A direct assay of the phage DNA injection using ³²P] labelled phage, showns that Ca²⁺ ions are necessary for the injection process. The injection itself is a slow process and takes 15 min to complete at 37°C. The bacteria infected in presence of Ca²⁺ tend to abort if the ions are subsequently withdrawn from the growth medium. The effect of calcium withdrawal is maximally felt during the early part of the latent period; however, later supplementation of Ca²⁺ ions salvage phage production and the mature phage progeny appear after a delayed interval, proportional to the time of addition of Ca²⁺.Abbreviations moi multiplicity of infection - PFU plaque forming units - EGTA ethylene-glycol-bis (-aminoethyl ether) N,N-tetraacetic acid