224 PROTEIN (NITROGEN) METABOLISM OF BACTERIA 



coli, but the greater ease with which glucose is broken up enables the organism to 

 draw upon the glucose more easily for most of its carbon supply, and to this extent 

 leave the nitrogenous substrates intact. 



Berman and Rettger' and later Slanetz and Rettger- observed that while B. subtil- 

 is readily attacks glucose in ordinary broth, the glucose does not prevent or materially 

 retard nitrogen metabolism of this organism. In fact, the proteolytic activity seems 

 to be accelerated by the glucose. This may be explained by the very active proteolytic 

 property of B. suhtilis, and the simultaneous production of acid and alkali in pro- 

 portions which tend to neutralize each other, and thus permit proteolysis to continue. 



Other members of the subtilis group, B. cereiis and B. megatherium, are greatly 

 retarded in their nitrogen metabolism by glucose, even in the presence of i per cent 

 phosphate buffer, and in this respect they resemble Bact. coli, Bad. typhosum, and 

 the paratyphoids, to a certain degree. 



PROTEIN SYNTHESIS BY BACTERIA 



Chlorophyll-bearing plants synthesize their cell substance with the aid of the 

 sun's energy. Bacteria must obtain their energy by purely chemical action. Syn- 

 thesis involves energy utilization. Analysis or katabolism is accompanied by the 

 liberation of energy. Carbon plays the chief role in these processes; in some instan- 

 ces the necessary energy is provided by the oxidation of nitrogen (nitrification) and 

 of sulphur. 



Amino acids serve as a common source of nitrogen for bacteria. The exact nature 

 of the process is still little understood, but it must be assumed that it takes place 

 in the cell, and that the amino acids are deaminized to furnish ammonia directly, and 

 that a very intensive selective action takes place in which the necessary chemical 

 elements are used for energy and the building up of the complex cell substance, par- 

 ticularly proteins, and whereby those elements or atomic groups which are useless are 

 eliminated or rejected and constitute the so-called "metabolic waste products" of 

 the bacterial cell. 



Simple amino acids often serve as the only source of organic nitrogen, as, for ex- 

 ample, asparagin in the synthetic medium of Jordan^ and the same amino acid in 

 Frankel's modification of the Uschinsky medium. Glycocoll and other simple amino 

 acids have also been used to furnish the necessary conditions. Thus a single amino 

 acid may supply the nitrogen needs for building up the complex nitrogenous substan- 

 ces of the cell which themselves contain simple and complex amino acids of almost 

 endless description, and the purin bases which characterize the nuclear substance. 



Turin bases serve as sources of nitrogen in some instances. Koser^ found that the 

 aerogenes type of the coli-aerogenes group can attack uric acid and hypoxanthine, 

 whereas the coli type cannot. There is no reason to assume, however, that these purin 

 bases are converted directly into the nuclear substance of the cell. 



On the other hand, there are many organisms which require the most complex 



' Ihid. 



' Manuscript in preparation. 



3 Jordan, E. O.: /. Expcr. Med., 4, 627. 1899. 



* Koser, S. A.: J. Infect. Dis., 23, 377. 1918. 



