106 CHEMISTRY OF BACTERIA AND THEIR PRODUCTS 



been demonstrated. (The chemotactic influence of bacteria upon 

 leucocytes is discussed in Chapter x.) 



CHEMICAL COMPOSITION 



This varies greatly, not only between different species, but 

 even in the same species grown on different media ; in this re- 

 spect bacteria are much more modified by their environment than 

 are higher organisms. Grown on a salt-rich medium they yield 

 much ash ; grown on a peptone-rich medium they contain much 

 proteid ; grown on a fat-rich medium they contain much material 

 soluble in ether. Cholera vibrios grown on a bouillon medium 

 contained 69.25 per cent, of proteid, and 25.87 per cent, of 

 ash, whereas the same organism grown on Uschinsky's medium, 

 which contains no proteids but only various simple chemical 

 compounds, 1 contained but 35.75 per cent, of proteid and 13.7 

 per cent, of ash (Cramer). Even in the same medium two 

 different strains of the same organism may show equally great 

 differences : Two strains of cholera vibrios grown on the same 

 medium showed respectively 65.63 per cent, and 34.37 per 

 cent, of proteid. It is evident, therefore, that quantitative 

 analyses of bacteria show nothing as to their nature, and on 

 account of the extreme limits of their variation are practically 

 valueless. 



Qualitatively the variations are not so great all bacteria 

 contain proteids, lipoid substances, and salts, of which phos- 

 phates are most prominent in the ash. The older analyses of 

 bacterial constituents are of little value. Recent studies prove 

 that the chief constituent of the cell contents is a true nucleo- 

 proteid (Iwanoff 2 ) containing some sulphur and iron ; probably 

 many of the " pyogenetic proteids," " bacterial toxalbumins," 

 " bacterial caseins " of earlier investigators are true nucleopro- 

 teids. In a water bacillus Nishimura found xanthin, guanin, 

 and adenin, indicating the presence of nucleoproteid ; others 

 have found that bacterial nucleoproteid s split off pentoses, as do 

 the nucleoproteids of higher cells. Mary Leach 3 found evidence 

 that the colon bacillus is largely made up of nuclein or glyco- 

 nucleoproteids, but contains no cellulose. Other proteids, 

 namely, globulins and nucleo-albuinins, have also been described 



1 Uschinsky's medium is: Water, 1000 parts; glycerin, 30-40; sodium 

 chloride, 5-7 ; calcium chloride, 0.1 ; magnesium sulphate, 0.2-0.4; di-potas- 

 sium-phosphate, 0.2-0.25 ; ammonium lactate, 6-7 ; sodium asparaginate, 3-4 

 parts. 



2 Hofmeister's Beit., 1902 (1), 524. 



3 Jour. Biol. Chem., 1906 (1), 463. Full bibliography on Chemistry of Bac- 

 teria. 



