48 



VIRAL PROTEIN AND NUCLEIC ACID IN BACTERIOPHAGE GROWTH 



this way may be related to those responsible for the release of bacterial com- 

 ponents from infected bacteria (Prater, 1951; Price, 1952). 



A variant of the preceding experiments was designed to test bacteria at a 

 later stage in the growth of phage. For this purpose infected cells were aerated 

 in broth for 5 or 15 minutes, fixed by the addition of 0.5 per cent {v/v) com- 

 mercial formalin, centrifuged, resuspended in 0.1 per cent formalin in water, 

 and subsequently handled as described above. The results were very similar 

 to those already presented, except that the release of P^^ from the cells was 

 slightly less, and titrations of infected cells could not be made. 



The S^^-labeled material detached from infected cells in the manner de- 

 scribed possesses the following properties. It is sedimented at 12,000 G, though 

 less completely than intact phage particles. It is completely precipitated by 



TABLE V 



Eifect of Mulliplicily of Infection on Elution of Phage Membranes from Infected Bacteria 



The infected bacteria were suspended at 10' cells per ml. in water containing per liter 

 1 mM MgSO^, 0.1 mM CaCla, and 0.1 gm. gelatin. Sampjes were withdrawn for assay of 

 extracellular isotope and infected bacteria before and after agitating the suspension. In 

 either case the cells spent about 15 minutes at room temperature in the eluting fluid. 



antiphage serum in the presence of whole phage carrier. 40 to 50 per cent of 

 it readsorbs to sensitive bacteria, almost independently of bacterial concen- 

 tration between 2 X 10^ and 10^ cells per ml., in 5 minutes at 37°C. The ad- 

 sorption is not very specific: 10 to 25 per cent adsorbs to phage-resistant bac- 

 teria under the same conditions. The adsorption requires salt, and for this 

 reason the efficient removal of S^^ from infected bacteria can be accomplished 

 only in a fluid poor in electrolytes. 



The results of these experiments may be summarized as follows: — ■ 



1. 75 to 80 per cent of the phage sulfur can be stripped from infected cells 

 by violent agitation of the suspension. At high multiplicity of infection, nearly 

 50 per cent elutes spontaneously. The properties of the S^^-labeled material 

 show that it consists of more or less intact phage membranes, most of which 

 have lost the ability to attach specifically to bacteria. 



2. The release of sulfur is accompanied by the release of only 21 to 35 per 



96 



