246 G. S. STENT 



they yield a very liigh burst of progeny phage particles, which can sometimes 

 attain an average of more than a thousand per cell. "Rapid lysis," or r, 

 mutants of the T-even strains occur, however, which do not produce lysis 

 inhibition, in that bacteria primarily infected with such r mutants lyse at the 

 normal time, whether or not superinfected with additional phage particles 

 prior to the end of the latent period, even if the superinfecting particles are 

 of the wild r+, or lysis-inhibiting type (Doermann, 1948a). Bacteria primarily 

 infected with r+ phages, however, will manifest lysis inhibition even if 

 superinfected with rapid lysis r mutants (Stent and Maah^e, 1953). One may 

 infer, therefore, that the intracellular growth of the r+ wild type bacterio- 

 phage causes the host cell to degenerate in a way different from that engender- 

 ed by the growth of the r mutants, so that in the former case the adsorption 

 of r+ or r particles at late stages of the latent period strengthens the cell, or at 

 least retards further degeneration, thus postponing the moment of ultimate 

 disruption by the internal pressure. Lysis inhibition, although its mechanism 

 is still poorly understood, has been an extremely useful tool in both genetic 

 and biochemical studies of bacteriophage reproduction, since it allows harvest 

 of additional infective progeny particles constituted from bacteriophage 

 substance abeady present in an "incomplete" form at the time of normal 

 lysis (Levinthal and Visconti, 1953; Stent and MaaWe, 1953). 



D. The Eclipse 



Although the one-step growth experiment demonstrated clearly the general 

 nature of the process by which bacterial viruses multiply within cultures of 

 susceptible bacteria, it only brought into focus rather than answered the 

 question of more fundamental biological interest, namely, what is actually 

 going on inside of the infected cell during the latent period whUe the parental 

 phage particle manages to cause its own several hundredfold reduplication. 

 One important point relevant to this question is naturally the manner in 

 which the number of phage particles present within the infected cell increases 

 from the moment of infection until the time of lysis. This information can be 

 obtained by breaking open the infected cells at various times during the 

 latent period and assaying the infectivity of the material released by 

 premature lysis. Such an experiment was undertaken by Doermami (1948b, 

 1952), who infected bacteria with T4 phages under the conditions of the one- 

 step growth experiment and induced lysis-from-without of aliquots of the 

 infected culture at various times after infection by addition of cyanide and a 

 large excess of T6 phages. Doermann then assayed these artificial lysates for 

 their content of infective T4 particles by use of indicator bacteria resistant 

 to the action of the T6 employed for lysis-from-without. The result of 

 Doermann's experiment was that the infectivity associated with the original 



