60 BACTERIOLOGICAL CHEMISTRY 



as judged by its ability to stain with those aiiihne dyes 

 which stain cliromatin in the higher plants. The nitro- 

 genous constituents of protoplasm fall into three groups : 

 (a) simple proteins, (b) amino -acids derived by the break- 

 down of proteins and (c) the nucleoproteins. 



The bacteria and yeasts appear to contain proteins 

 of the globulin and albumin types if solubility in buffer 

 solutions of laiown pH. and the concentrations of 

 ammonium sulphate required to precipitate the fractions 

 are used as criteria. Globulin is precipitated from 

 solution by the addition of ammonium sulphate to 50 

 per cent, of saturation. Albumin is soluble in this 

 concentration of ammonium sulphate, but is precipitated 

 when solutions are saturated with the salt. Globulin 

 can be separated into euglobulin, which is insoluble in 

 distilled water, and pseu do -globulin which is soluble. 

 Partially degraded proteins, protamines, peptones and 

 polypeptides are also present, as well as such conjugated 

 proteins as glycoproteins, phosphoproteins, lecitho- 

 proteins and nucleoproteins. 



The amino -acids obtained on hydrolysis of bacterial 

 and yeast proteins include all the common ones found in 

 proteins from other sources. The amino-acids proline, 

 phenylalanine and tyrosine appear to be absent from 

 the proteins of moulds. 



The nucleoproteins, which are all soluble in dilute 

 alkali and which are precipitated from such solution by 

 acid, constitute about 2 to 3 per cent, of the dry weight 

 of bacteria. On hydrolysis those of the tubercle bacillus 

 give a mixture of the pyrimidine and purine types of 

 nucleic acid, but those of most other bacteria give the 

 purine type only. The yeast nucleoproteins are like those 

 of the tubercle bacillus in yielding both types of nucleic 

 acid. The nucleoproteins of the moulds appear to have 

 escaped examination. The metachromatic granules or 

 volutin found in many bacteria, yeasts and moulds 

 (particularly in the diphtheria bacillus) appear to be 



