38. BIOSYNTHESIS OF PROTEINS IN BACTERIAL CELLS 419 



wall by the action of lysozyme, 48, 49 or by penicillin, 80 or by treatment with alkali. 81 

 The membrane is a lipoprotein, the structure of which has been studied by Mandel- 

 stam et al.* 2 The wall or the pure membrane contains no nucleic acids but it includes 

 pentose -containing substances such as ribityl phosphates. 83 - 84 



The synthesis of the mucopeptides of the wall and the synthesis of cytoplasmic 

 protein are two completely independent and dissociable processes in bacteria. Thus, 

 on the one hand, the synthesis of cytoplasmic protein, can take place in bacteria 

 lacking their cell walls (protoplasts), 85 or in bacteria in which synthesis of the cell 

 wall is blocked by penicillin. 86 The converse is also true; the formation of mucopep- 

 tides can be observed in the absence of synthesis of cytoplasmic proteins. 87 



III. Synthesis of Macromolecular Components during Normal 

 Bacterial Growth 



Since each metabolic process in the cell is integrated in a very precise 

 manner, it is difficult to obtain information about the relationship between 

 nucleic acid and protein synthesis from a study of the normal cell. To ob- 

 tain such information one has to interfere specifically with the synthesis 

 of a particular component by the use of an inhibitor or by selective modifi- 

 cation of the medium; this type of experiment will be considered later in 

 this review in the study of the "uncoupled synthesis." 



However, the study of the behavior of normal bacteria does reveal some 

 important aspects of the biosynthesis of macromolecules, such as the de- 

 gree of metabolic renewal of the protein and of the nucleic acids, the rate 

 of their formation, and the nature of the intermediate steps. 



1. Metabolic Stability of Proteins and Nucleic Acids 



Before considering the kinetics of protein and nucleic acid biosynthesis 

 in bacteria, it is necessary to discuss the question of "turnover" in these 

 macromolecules (see also Chapter 37). 



Monod and Cohn 88 and Hogness, Cohn, and Monod 89 showed a few years 

 ago that when bacteria are first labeled in their protein by growing in the 

 presence of S 35 , then washed and transferred to a nonradioactive medium 



80 J. Lederberg, Proc. Natl. Acad. Sci. U. S. 42, 574 (1956). 



8 ' N. D. Zinder and W. F. Arndt, Proc. Natl. Acad. Sci. U. S. 42, 586 (1956). 



82 J. Mandelstam and H. J. Rogers, Nature 181, 956 (1958). 



83 J. J. Armstrong, J. Baddiley, J. (1. Buchanan, B. Carss, and G. R. Greenberg, 

 J. Chem. Soc. p. 4344 (1958). 



84 J. J. Armstrong, J. Baddiley, J. G. Buchanan, and B. Carss, Nature 181, 1692 

 (1958). 



85 K. McQuillen, in "Bacterial Anatomy," p. 127. Cambridge Univ. Press, London 

 and New York, 1956. 



86 F. Gros and M. Macheboeuf, 6th Intern. Congr. Microbiol., Rome p. 38 (1953). 



87 A. R. Crathorn and G. D. Hunter, Biochem. J. 69, 47 (1958). 



88 J. Monod and M. Cohn, 6th Intern. Congr. Microbiol., Rome p. 4 (1953). 



89 D. S. Hogness, M. Cohn, and J. Monod, Biochim. et Biophys. Acta 16, 99, (1955). 



