COMPOSITION OF BACTERIA 103 



CHEMICAL COMPOSITION 



This varies greatly, not only between different species, but even 

 in the same species grown on different media ;^ in this respect bacteria 

 are much more modified by their environment than are higher or- 

 ganisms. On the other hand, they can develop in solutions containing 

 only a few of the simplest organic and inorganic compounds and syn- 

 thesize the complex components of their cells, as well as enzymes, 

 toxins, pigments.^ They usually contain between 80 and 90 per cent, 

 of water. Grown on a salt-rich medium they yield much ash; grown 

 on a peptone-rich medium they contain much protein; grown on a fat- 

 rich medium they contain much material solulile in ether. Cholera 

 vibrios grown on a bouillon medium contained 69.25 per cent, of pro- 

 tein, and 25.87 per cent, of ash, whereas the same organism grown on 

 Uschinsky's medium, which contains no proteins but only various 

 simple chemical compounds, contained but 35.75 per cent, of protein 

 and 13.7 per cent, of ash (Cramer). Even in the same medium two 

 different strains of the same organism may show equally great dif- 

 ferences: Two strains of cholera vibrios grown on the same medium 

 showed respectively 65.63 per cent, and 34.37 per cent, of protein. 

 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. The specific gravity of bac- 

 teria, generally between 1.12 and 1.345, also varies wdth media and 

 age.^ In an electric field they move towards the anode. ^"^ 



Qualitatively the variations are not so great — all bacteria contain 

 proteins, lipoid substances, and salts, of which phosphates are most 

 prominent in the ash. The character of the proteins and fats of 

 bacteria grown on peptone bouillon is quite the same as when they 

 are grown on protein-free media.'' The older analyses of bacterial 

 constituents are of little value. Recent studies prove that the chief 

 constituent of the cell contents is a true nucleoprotein (Iwanoff^^) con- 

 taining some sulphur and iron; probably many of the "pyogenetic pro- 

 teins," "bacterial toxalbumins," "bacterial caseins" of earlier investi- 

 gators are true nucleoproteins.^^ The stainable substance of anthrax 

 bacilli behaves as if it were a chromatin, while the spores resemble 



^ See Dawson, Jour. Bact., 1919 (4), 133. 



^ Concerning fundamentals of nutrition of bacilli see Koser and Rettger, Jour. 

 Infect. Dis., 1919 (24), 301; Long, Amer. Rev. Tuberc, 1919 (3), 86. 

 9 Stigell, Cent. f. Bakt., 1907 (43), 487. 



'" Buxton, Zeit. physikal. Chem., 1906 (57), 47; Girard and Audubert, Compt. 

 Rend. Acad. Sci., 1918 (167), 301. Concerning the decirical condxiclivity of 

 bacteria see Thornton, Proc. Royal Soc, London, Sec. B., 1913 (85), 331. 



" Tamura, Zeit. physiol. Chem., 1913 (88), 190. 



'- Hofmeister's Beitr., 1902 (1), 524; bibliography by Lustig, KoUe and Wasser- 

 mann'8 Handbuch, 1913 (ii), 1362. 



' ' The purity of many of the preparations worked with as bacterial nucleopro- 

 teins, is very doubtful. (See Wells, Zeit. Immunitat., 1913 (19), 599.) 



