Evidence for heterogeneity in populations of T5 bacteriophage.

Each T5 stock contains a population of particular phages that, just after adsorption onto the host bacteria. release their entire chromosome outside the bacterial membrane in a place where it is sensitive to bacterial enzymes. This release takes place before the sensitization step to deprivation of calcium and before the transfer of the first-step DNA fragment. Secondarily, this released DNA is degraded by bacterial enzymes, mainly by the endonuclease I; the products of degradation are spontaneously released in the surrounding medium. Thus, in each T5 phage stock it seems that there is a minor population that is deficient for the mechanism of controlled DNA injection into the bacteria.