332 BACTERIOLOGICAL CHEMISTRY 



Tobacco mosaic vims has tlie composition of a 

 nucleoprotein of the yeast type, containing ribose, 

 guanine, cytosine, adenine and uridylic acid. The 

 protein portion contains 9-0 per cent, arginine, aspartic 

 acid, cysteine, glutamic acid, leucine, lysine, 6-7 per 

 cent, of phenylalanine, 4-7 per cent, of proline, 6-4 per 

 cent, of serine, 5-3 per cent, of threonine, 4-5 per cent, of 

 tryptophane and 3-9 per cent, of tyrosine. Alanine, 

 glycine and histidine appear to be absent. No lipoid 

 material could be detected. 



Besides the proteins, the protoplasm of micro-organ- 

 isms contains the nucleoproteins and nucleins which 

 constitute the nuclear material of the cell. This may be 

 dispersed more or less uniformly throughout the cell 

 contents, as in most bacteria, or it may be collected in 

 granules as in the metachromatic or volutin granules of 

 the diphtheria bacillus, or in true nuclei as in the yeasts. 



The nucleoproteins are soluble in dilute alkali, and are 

 precipitated from such solutions by dilute acids. They 

 constitue about 2 or 3 per cent, of the dry weight of 

 bacteria. 



The nucleoproteins are complex molecules which break 

 down on hydrolysis to yield a basic protein — histone or 

 protamine — and nuclein. Nuclein on hydrolysis breaks 

 down further to yield another protein and a nucleic 

 acid. Nucleic acids on hydrolysis with cold alkali are 

 degraded into nucleotides. There are two main types of 

 nucleotide (a) those derived from yeasts and plants and 

 (6) those derived from animals. The yeast nucleic acids 

 are made up of guanylic acid, 



CH C— N 



adenylic acid, ! li % 



CH, -' II li CH 



II II / 



N (3— N.R 



