^36 J- D. WATSON, O. MAAL0E VOL. 10 (1953) 



of Table III further shows that with increasing intervals between primary and secondary 

 infection, the amount of ^^p which stays attached to the bacteria decreases. Since the 

 labelled phages adsorb at the normal rate, most of the ^^p in the supernate of the 

 infected cells must initially have been adsorbed onto the cells. The observed increase 

 in unadsorbed material is probably an expression of the breakdown of secondarily 

 adsorbed particles described by Leslie, French, Graham, and Van Rooyen^. These 

 authors observed that a primary infection stimulates within a few minutes the infected 

 cell in such a way that, if a new phage particle adsorbs, it is broken down extensively 

 on the surface of the bacterium, releasing about 50% of its phosphorus into the medium 

 in the form of material soluble in 5 % trichloroacetic acid. 



This stimulation phenomenon is of further importance for transfer experiments, 

 since we must assume that early released progeny particles which adsorb on unlysed 

 cells will be broken down and release half their phosphorus into the medium. In most 

 of the previous work adsorption of progeny particles was not prevented and the break- 

 down effect presumably decreased the transfer values. Since in our experiments ad- 

 sorption was blocked by antibacterial serum, the 50% transfer values can be taken as 

 a good estimate of the transfer to all the progeny particles. 



TABLE III 



DISTRIBUTION OF ^^P FOLLOWING SECONDARY INFECTION OF B/l BY LABELLED T^T 



Growing bacteria concentrated to 1.3-10® cells/ml in broth were infected at i = o, with an 

 average of 5 unlabelled T4r particles. At various intervals, labelled T4r was added at a ratio of 

 I particle per bacterium. Several minutes after the addition of the labelled phage, unadsorbed ^^P 

 was removed by low speed centrifugation and the infected bacteria resuspended in nutrient broth 

 at a concentration of 10* cells/ml. 



Minutes between 



primary and secondary 



infection 



% of parental radioactivity in 



05 



* This material must initially have been adsorbed but has been released again because of the 

 breakdown effect described by Lesley et al.^. 



Isotope transfer from parental to progeny Tj 



At the salt concentration usually employed in growth media, T3 phage adsorbs 

 rather slowly. To ensure the necessary rapid adsorption of the labelled T3 particles, 

 the NaCl concentration in the adsorption tube had to be lowered to 0.05%. At this 

 low salt concentration, over 99% of the infecting particles adsorbed within two minutes. 

 Except for this modification, the experiments were like the T4 experiments and included 

 characterization of the progeny by serum precipitation and adsorption on sensitive 

 bacteria. Table IV shows that about 40% of the parental ^ap was transferred. Since 

 nearly simultaneous adsorption of the infecting phage particles and isolation of the 

 entire progeny were achieved, we may consider the transfer value of about 40% as a 

 maximum value. As in the case of the phages T2 and T4, the transfer of phosphorus 

 is incomplete. 

 References p. 442. 



109 



