CHAPTER XV 

 PROTEIN (NITROGEN) METABOLISM OF BACTERIA 



LEO F. RETTGER 

 Yale University 



Although single-celled and among the smallest known living organisms, bacteria 

 can effect the most elaborate syntheses, and through a multiplicity of enzymatic and 

 catalytic processes reduce to their elements the most complex organic substances: 

 proteins, fats, and polysaccharides. Their range of activities may be said to be almost 

 unlimited. 



PROTEINS AND THE LIVING CELL 



Protoplasm defies analysis, for when it is subjected to chemical study it is no 

 longer protoplasm, but dead tissue. Our knowledge of the internal structure and of 

 the chemical composition of the bacterial cell is as yet very meager. However, suf- 

 ficient studies have been made of the chemistry of bacteria to leave no doubt of the 

 importance of proteins and protein-like substances, and to show that the bacterial 

 cell is in this respect not very unlike those of the higher forms of life, both animal and 

 vegetable. 



According to the observations of Nicolle and Allilaire,' and of various other in- 

 vestigators, organic nitrogenous material (protein) in bacteria greatly preponderates 

 over the non-nitrogenous. It has been found, however, that the quantitative chemical 

 composition varies markedly among different organisms, and even within the same 

 species. 



Cramer^ has shown that the amount of total solids, ash, protein, and non-nitrog- 

 enous matter present in bacterial cells varies with the composition of the culture medi- 

 um, though not in direct proportion; also with the age of culture, and incubation tem- 

 perature. For example, he determined the protein content of the cholera vibrio to 

 be 65 per cent of the total solids, when grown in plain infusion peptone broth, as com- 

 pared with 45-50 per cent in Uschinsky's medium. 



It appears to be an established fact that different bacterial species or groups 

 possess certain chemical entities which distinguish them from all other forms. For in- 

 stance, the acid fast group contains a relatively large proportion of ether-soluble, 

 fat-like substances, and the different pathogens elaborate intracellular toxins and 

 antigenic substances which distinguish them from each other. 



Nicolle and Allilaire^ determined the nitrogen content of certain organisms to be 

 as follows (in per cent): V. cholerae, 9.79; Bact. dysenteriae, 8.89; Bad. typhi, 8.28; 

 Bad. colt, 10.32; P. vulgaris, 10.73; B. anthracis, 9,22; E. prodigiosus, 10.55; -^•^• 



' Nicolle, M., and Allilaire, E.: Ann. de VInst. Pasteur, 23, 547. 1909. 

 * Cramer, E.: Arch. f. Ilyg., 16, 151. 1893; 22, 167. 1895. 

 3 Nicolle, M., and Allilaire, E. : loc. cil. 



218 



