44 METABOLISM 



1937a, h). The presence of various amino-acids in detectable amounts, and their quanti- 

 tative relationship, might be largely influenced by the media employed for growth. The 

 cultural conditions, for example, which lead to a diminution in the capsule formation 

 of the anthrax baciUus would markedly diminish its content of c?(-)-glutamic acid, and 

 with certain strains, growth in an atmosphere containing 20 per cent.COg markedly increases 

 capsule formation (Ivanovics 1937). But Tamura (19136) records closely similar figures 

 for the mono-amino-nitrogen and basic amino-nitrogen in cultures of an acid-fast bacillus 

 grown in nutrient broth and on a synthetic medium. In any case the findings recorded 

 above give a very incomplete picture. Detailed and comprehensive analyses have, for 

 the most part, still to be made. 



There is one further point in connection with the nitrogenous constituents of bacterial 

 cells, on which all observers are agreed — their high content in nucleo-proteins. (See 

 Nishimura 1893, Galeotti 1898, Aronson 1900, Stoklasa 1908, Tamura 1913a, Schaffer 

 et al. 1922, Buchanan and Fulmer 1928-30, Boivin and Mesrobeanu 1934, Sevag, Smolens 

 and Lackman 1940, Stokinger, Ackerman and Carpenter 1944.) The presence of nucleins 

 had been suspected by many of the earUer bacteriologists because of the affinity of bacterial 

 cells for nuclear stains ; and the work of the observers quoted above, and of others, has 

 confirmed this conclusion by direct chemical analysis. Such substances as guanine, 

 xanthine, hypoxanthine and adenine have frequently been demonstrated, and the high 

 content of phosphorus has been noted above. Boivin and Mesrobeanu (1934) and Mesro- 

 beanu (1936) report that the purine nitrogen of undried cells varied from 0-18 to 0-29 

 per cent, among six species examined, being about 10 per cent, of the total bacterial 

 nitrogen. Of this purine nitrogen 73-94 per cent, was in the form of nucleic acid, the 

 rest being made up of nucleotides, nucleosides and free purine bases. 



Both ribonucleic acid (the " yeast " type nucleic acid) and desoxyribonucleic acid 

 (the "thymus" type of nucleic acid) have been isolated from bacteria. Coghill (1931) 

 isolated ribonucleic acid from Myco. 'pJiIei, Heidelberger and Kendall (1931) from strejDto- 

 cocci, and Thompson and Dubos (1938) from pneumococci, of which it constituted 

 2-5 per cent, of the dry weight. Nucleic acid of the desoxyribose type occurs in Bad. coli 

 (Schaffer et al. 1922) and Myco. tuberculosis (Johnson and Brown 1922). Sevag, Smolens 

 and Lackman (1940) found 20 per cent, of the dry weight of Str. pyogenes to be nucleic 

 acid, and identified 10-30 per cent, of it as of the desoxyribose type (see also p. 306). 

 The gonococcus also contains about 20 per cent, of nucleic acid (Stokinger et al. 1944). 



Carbohydrate Constituents of Bacterial Cells. — Buchanan and Fulmer quote 

 total carbon figures ranging from a little below to a little above 50 per cent, dry 

 weight for various bacterial species, with one widely discrepant finding. The 

 significance of this figure in relation to carbohydrate content is dubious. The 

 actual carbohydrate content is probably a great deal lower, and the content of 

 polysaccharides is certainly lower. In their analysis of the gonococcus, Stokinger, 

 Ackerman and Carpenter (1944) found 5-9 per cent, of the dry weight was carbo- 

 hydrate. We have ourselves observed crude polysaccharide yields of between 

 5 and 20 per cent, from over thirty different strains of Proteus vulgaris. 



There is very little evidence that bacteria share with the majority of vegetable 

 cells the capacity of forming a cellulose envelope, or that cellulose enters in any 

 way into their composition (see Buchanan and Fulmer 1928-30.) They do, how- 

 ever, form a variety of polysaccharide gums ; and the .studies of recent years 

 have shown quite clearly that complex polysaccharides are of common occurrence 

 in the surface layers of bacterial cells, and in their capsules when these are present. 

 These polysaccharides play an important, often a dominant, part in determining 

 antigenic specificity (see Chapter 8). 



We have noted in the preceding chapter that certain bacteria may contain 

 granules that have been variously identified, on the basis of staining reactions, 



