INTRACELLULAR MULTIPLICATION OF BACTERIAL VIRUSES 249 



III. Synthesis of the Bacteriophage Progeny Substance 



In a well-ordered kitchen, the basic cooking is done before the first course is served. 

 Liiria (1950). 



A. Incomplete Bacteriophages 



The premature lysis experiment of Doermann followed the intracellular 

 growth of the bacteriophage by assay of the intracellular number of infective 

 phages, i.e., of progeny structures already endowed with the power of self- 

 reproduction, the most complex of all the properties of the virus particle. 

 Further insight into the process of phage multiplication was gained by the 

 discovery of a variety of "incomplete" phage structures in premature lysates 

 of phage-infected bacterial cultures. These structures are incomplete in 

 the sense that they possess one or another of the properties of the virus 

 without being endowed with the ability to cause plaques when plated for 

 assay on a plate seeded with sensitive indicator bacteria. Two possible 

 interpretations offer themselves as to the nature of the incomplete bacterio- 

 phages. They could, on one hand, be phage precursors, i.e., represent develop- 

 mental stages in the ontogeny of the virus particle. In order to qualify for 

 consideration as a phage precursor, any given type of incomplete structure 

 should appear before the mature phage particles and later be incorporated 

 into them in the subsequent course of intracellular growth. Some of the 

 incomplete structures, on the other hand, could also represent by-products of 

 phage reproduction or abortive attempts to construct intact phages, in which 

 case they would not be destined to form part of the future infective progeny. 



1. Sedimentation, Adsorption, and Precipitation 



Three properties which set bacteriophages apart from other structures 

 present in the host bacterium are their sedimentability , their adsorbability, and 

 their antiserum precipitability. Because of their size, shape, and density, 

 T-even bacteriophages move in centrifugal fields with sedimentation 

 velocities unlike those of any other materials present in the host bacterium. 

 Hence, phage particles can be readily separated from the general debris 

 present in lysates by differential centrifugation (cf. Chapter 3, Vol. I). 

 Second, because of the attachment organs resident in their tail, bacteriophages 

 are specifically adsorbed to bacterial cells, so that if a suspension of sensitive 

 bacteria is introduced into a phage lysate, only the phage particles but not the 

 host-cell debris will be fixed (cf. Chapter 6, Vol. II), Finally, because bacterio- 

 phages are generally good antigens and exhibit a rigorous serological 

 autonomy, they can be precipitated specifically with antiphage serum, so that 

 if antiphage serum previously exhausted against bacterial host material is 

 added to a phage lysate, the phage particles but not the debris will be precipi- 

 tated by the antigen-antibody reaction (cf. Chapter 10, Vol. I). It is, therefore, 



