Abstract
The synthesis of protein and nucleic acids in cells of ultraviolet irradiated Escherichia coli were studied with or without infection of bacteriophage T2r+ using 35S or 32P as tracer. The synthetic capacity of host cells was lost at considerably lower doses of irradiation than the synthetic capacity for bacteriophage particles. The synthesis of RNA by infected cells appeared to be little inhibited by irradiation of relatively high dose.
The experiments were performed in which bacteriophage T2 was infected to either unirradiated or heavily irradiated (15w, 30cm, 5 minutes) bacteria and incorporation of isotopes was studied with the following results;
(1) The RNA which is synthesized in irradiated bacteria-phage system is quite similar to that produced by normal infection in its quantity, turnover, and nucleotide composition.
(2) The rate of synthesis of protein and DNA by irradiated coliphage system is reduced to about one half to one third of normal infection.
(3) The amount of non-phage protein which is synthesized by irradiated cell-phage system is apparently less than that by normal infection, at least during the first 15 minutes' incubation. Later, however, the former exceeds the latter.
(4) Nearly the same amounts of phage antigenic protein and of DNA are accumulated at the time of the appearance of intracellular bacteriophage (13 minutes by unirradiated cell-phage system and 35 minutes by irradiated cells-phage system).
The following may be concluded from these results.
(i) Phage maturation occurs after the accumulation of certain amounts of phage precursors in host cells. The pool size of phage precursors in bath systems are the same at that time.
(ii) Since the sysnthesis of precursors does not occur in excess, inactive phage particle does not appear to be formed.
(iii) Inhibition at the step of maturation cannot be expected by irradiated coli-phage system.
(iv) The observed increase in latent period and decrease in burst sized by irradiation of host cells may result from the reduction in the rate of synthesis of phage constitutents.
The reduction in the rate of synthesis of phage constituents has not been fully explained until now. This may be, however, attributed to either the reduction in the amount of nonphage protein synthesized in the early period or to the reduction in biological activity of this protein. This must be clarified by future studies.
