Abstract
The present paper describes some new host-range phenotypes of T4 phage, and their genetic control, regarding to the infectivity Of the virus against two different Shigella flexneri (which are originally resistant to T4), BI and BIII strains.
Fine structure of some genetic regions of T4 phage which control different host-range phenotypes of the phage was investigated by means of recombination procedure.
It has been demonstrated that the inheritance of the host-specificity of T4 is controlled by many genetic loci distributed fairly widely in T4 genome. They have been found being clustering at several different genetic regions, and all the mutations arising anywhere within one of these regions lead to similar phenotypic effect, whereas each region controls different phenotypes, respectively.
Some of the h mutants have a very favorable property which allows the study on the fine genetic structure of the h region by a selective technique. The smallest recombination value so far as observed was about 0.05-0.1 per cent recombination units, suggesting that the size of the elementary unit controlling the host-specificity of the virus is not larger than roughly 10 nucleotide pairs length.
All the h mutants descrived here did not invade K12 (λ)/4 and B/4 bacteria.
