.}.->() 



(HAITI K 26 



E. coli have been isolated. Some of these 



arc ultraviolet inducible, others are not. All 

 (seven) of the viruses whose prophages arc 

 inducible occupj different chromosomal loci 



located in one region of the host chronic 

 some (Figure 26-10). These phages also 

 differ from each other in that a host lysogenic 

 for one can still be infected by any o\' the 

 others 



Hemophilus influenzal' is transformable 

 and can also be infected by the UV-inducible, 

 temperate phage HP1. The genetic material 

 o\ this phage can be introduced into nonlyso- 

 genic Hemophilus competent for transforma- 

 tion in three ways: by injection from intact 

 phage; by infection with pure phage DNA; 

 and by infection with pure bacterial DNA 



"' The preceding discussion is based primarily 

 upon work of F. Jacob and E. L. Wollman 

 (1957). of A. D. Kaiser and F. Jacob (1957). 

 and of F. Jacob and A. Campbell. 



carrying the prophage, isolated from lyso- 

 Lvns. In each case, the host cell either be- 

 comes lysogenic or lyses and liberates mature 

 phage progenj . 



Although the immunity properties oi' pro- 

 phage are controlled by a small portion of 

 the phage's total DNA content — the c, re- 

 gion — this region alone docs not include all 

 the genetic information or specifications 

 needed for prophage to become mature, in- 

 fective phage. Presumably most, if not all, 

 the other phage loci arc essential for the pro- 

 duction of mature phage, complete with its 

 protein parts. 



Using unlabeled host cells, crosses can be 

 made between genetically-different strains of 

 lambda, one unlabeled and the other labeled 

 with the isotopes C ,:: and N 15 . Following 

 density-gradient ultracentrifugation, the dis- 



11 See W. Harm and C. S. Rupert (1963). 



d2i 

 do 

 di8 

 di6 

 di4 



di7 



d34 d22 C CO I 



d32 d30/' / / 



im 



FIGURE 26-9. Diagrammatic representation of the linkage group of the tem- 

 perate bacteriophage X. The upper diagram shows the linear arrangement of 

 various markers for host range or plaque size or type. The d symbols refer 

 to specific defective mutants. The e region is marked by a thicker line and is 

 shown enlarged in the loner diagram. It is composed of three sub-regions, 

 (;,, (,, Co. Im refers to the segment controlling immunity. (After F. Jacob 

 and J. Monod. ) 



