FOOD RELATIONSHIPS OF BACTERIA 65 
up more than 7 to 10 per cent of the solid matter of the bacterial cell. 
The essential elements and the percentage of them found in the ash of 
certain bacteria have been referred to previously, and it was stated 
that the amount of inorganic salts found in the bodies of the bacteria 
bore a rather direct relationship to the salt concentration of the media. 
Of the inorganic elements, phosphorus is the most important, for it 
makes up nearly 50 per cent of the ash. Phosphorus in contradistinc- 
tion to any other inorganic salt is absolutely indispensable to bacterial 
growth. It is combined organically in nucleoproteins, glyco-nucleo- 
proteins and nucleic acids, which form the greater part of the protein 
of the bacterial cell. It is probable, although information is not avail- 
able at present upon this point, that phosphorus in combination with 
potassium and sodium as mono- and dihydrogen phosphates plays an 
important part in maintaining a reaction within the bacterial cell 
compatible with its viability.^ 
' Henderson, L. J.: Das Gleichgewicht zwischen Basen und Siiuren im tierischen 
Organismus, Ergeb. d. Physiol., 1909, 8, 254. 
