The Distribution of Parental Phosphorus Atoms Among Bacteriophage Progeny

Approximately half the deoxyribonucleic acid (DNA) contained in a population of T2, T4, or T6 bacteriophage particles reappears among the descendants ultimately issuing from phage-infected bacterial host cells. [1,2] This transfer is not due to the reincarnation of entire, intact parental DNA units in progeny guise, since at least half the DNA of each of those descendant particles which harbor the transferred atoms must be of nonparental origin. [3] For an understanding of the mechanisms involved in the reproduction of the hereditary structures of the bacteriophage, it is desirable to know the distribution of the parental atoms among the progeny population, i.e., the extent to which the atomic identity of the parental DNA has been conserved or destroyed. It is the purpose of this communication to present the results of experiments which indicate that most of the transferred phosphorus atoms of the parental DNA are distributed over at least 8 but no more than 25 of the progeny. A more detailed description of these results will be presented elsewhere. The basis of these experiments is that the bacteriophages lose their infectivity upon decay of radiophosphorus P32 incorporated in their DNA, the rate of inactivation being proportional to the number of P32 atoms per particle. [3] The fraction of P32 disintegrations which inactivate the T2 or T4 particles in which they occur is 0.10 at 40 C., this "efficiency of killing" having been established for "nonparental" radiophosphorus atoms, i.e., for those assimilated into the phage DNA from the phosphorylated constituents of host cell or growth medium. [3,4] Since neither the transferred phosphorus atoms nor those whose decay leads to inactivation appear to reside in any "special fraction" of the bacteriophage DNA, [4,5] it would seem reasonable that the decay of transferred P32 atoms should similarly inactivate the progeny particles harboring them. We have adopted this at present unprovable assumption and have endeavored to detect the presence of parental P32 atoms in the descendant phages by observing the lethal effects of the decay of these atoms on the progeny population