174 PHYSIOLOGY OF BACTERIA 



large molecules are not always put into the cell as such, 

 but are split and reshaped before fitting into the cell 

 architecture. This shaping must cause some waste 

 products. In many cases, these waste products of cell 

 construction may be used as food for energy; but there 

 are some instances known where this is not the case. 

 The only definitely established example is probably that 

 of the fusel oils in alcoholic fermentation which is 

 discussed in detail on p. 43. The yeast needs ammonia 

 for building its own proteins, and takes it from leucin, 

 leaving the rest of the molecule in the form of amyl 

 alcohol. 



The main reason why more such examples are not 

 known, is the small amount of these products. The 

 total dry weight of the cells of Bad. coli in 1 liter of a 

 full grown broth culture is only 220 mg. (Appendix p. 

 397). The waste products from the construction of 220 

 mg. of cells are likely to be less in quantity than the cell 

 weight; this means less than 0.02% of the weight of the 

 medium. 



It seems probable that the carbon dioxide produced 

 by some streptococci belongs into this category of 

 products. Hucker (1928a) mentions that Strept. lactis 

 produces about 70 mg. CO2 per liter. The dry weight 

 of the cells probably does not exceed 200 mg. The CO2 

 comes from peptone, and not from sugar; it must 

 originate from the decarboxylation of amino acids. 

 With other species of streptococci which produce more 

 carbon dioxide, there seems to be a distinct protein 

 metabolism established, and more amino-acids are split 

 than are needed for growth. 



Balls and Brown (1925) and Claassen (1927) during 

 the production of bread yeast observed a small amount 

 of a reducing substance which was not sugar, nor was it 



