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Independent Functions of Viral Protein and Nucleic Acid in Growth of Bacteriophage. September 20, 1952.

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Title:	Independent Functions of Viral Protein and Nucleic Acid in Growth of Bacteriophage [8 of 18]
Creator:	Chase, Martha
Contributor:	Hershey, Alfred Day, 1908
Publisher:	Journal of General Physiology
Date:	1952-09-20
Subject:	Molecular biology Molecular genetics
Description:	From the Journal of General Physiology Vol. 36, No. 1.
Type:	Text
Format:	text/plain
Language:	en
Identifier:	hersheychase-pg08.jpg
Source:	Master scanned with Epson GT-10000+ flatbed scanner at 600 dpi.
Rights:	http://osulibrary.orst.edu/specialcollections/coll/pauling/dna/copyright.html
Full Text:	46 VIRM. PROTEIN AND NUCLEIC ACID IN BACTERIOPIIAGE GROWTH 1. The unadsorbed fraction contained only 5 per cent of the original phage particles in infectioe form, and only 13 per cent of the total sulfur. (Much of this sulfur must be the material that is not adsorbable to whole bacteria.) 2. About 80 per cent of the phage was inactivated. Most of the sulfur of this phage, as well as most of the surviving phage, was found in the sediment fraction. 3. The supernatant fraction contained 40 per cent of the total phage DNA (in a form labile to DNase) in addition to the DNA of the unadsorbed surviving phage. The labile DNA amounted to about half of the DNA of the inactivated phage particles, whose sulfur sedimented with the bacterial debris. 4. Most of the sedimentable DNA could be accounted for either as surviving phage, or as DNA labile to DNase, the latter amounting to about half the DNA of the inactivated particles. Experiments of this kind are unsatisfactory in one respect: one cannot tell whether the liberated DNA represents all the DNA of some of the inactivated particles, or only part of it. Similar results were obtained when bacteria (strain B) were lysed by large amounts of UV-killed phage T2 or T4 and then tested with P3:-labeled T2 and T4. The chief point of interest in this experiment is that bacterial debris saturated with UV-killed T2 adsorbs T4 better than T2, and debris saturated with T4 adsorbs T2 better than T4. As in the preceding experiment, some of the adsorbed phage was not inactivated and some of the DNA of the inacti- vated phage was not released from the debris. These experiments show that some of the cell receptors for T2 are different from some of the cell receptors for T4, and that phage attaching to these spe- cific receptors is inactivated by the same mechanism as phage attaching to unselected receptors. This mechanism is evidently an active one, and not merely the blocking of sites of attachment to bacteria. Remo--eal of Phage Coats from Infected Bacteria.-Anderson (1951) has ob- tained electron micrographs indicating that phage T2 attaches to bacteria by its tail. If this precarious attachment is preserved during the progress of the infection, and if the conclusions reached above are correct, it ought to be a simple matter to break the empty phage membranes off the infected bacteria, leaving the phage DNA inside the cells. The following experiments show that this is readily accomplished by strong shearing forces applied to suspensions of infected cells, and further that in- fected cells from which 80 per cent of the sulfur of the parent virus has been removed remain capable of yielding phage progeny. Broth-grown bacteria were infected with Sas- or P'2-labeled phage in ad- sorption medium, the unadsorbed material was removed by centrifugation, and the cells were resuspended in water containing per liter 1 mm MgS0a, 0.1 m3I CaC11, and 0.1 gin. gelatin. This suspension was spun in a \'faring