366 



STATE BOARD OF AGRICULTURE. 



AMMONIA PRODUCTION IN PEPTONE SOLUTION. 



The mixed culture is taken from a similar peptone solution de- 

 composed by soil bacteria; the pure culture was obtained by plating 

 from this mixture. It was tried several times without success to get a 

 stronger ammonifying bacterium. This experience agrees with that of 

 others that in many fermentations the natural mixed culture is more 

 effective than the isolated pure cultures. The straight lines of these 

 curves are evident. 



I have only one plausible explanation for these lines. Instead of 

 the point of inflection we have a straight line. The point of inflection 

 is the moment where the organisms have reached their highest number. 

 In the first curves, the activity of bacteria soon decreased after this 

 point and the curve approached more and more the horizontal direction. 

 In these last experiments with soil bacteria, the bacteria maintained 

 their activity for quite a while after they had reached their highest 

 number. The abundance of food in milk, cheese, and similar products 

 made the bacteria less resistant to their own products than the scanty 

 food of soil extracts. 



This goes even so far that the bacteria in a poorer medium produce 

 a higher final concentration of fermentation products. We have sev- 

 eral experiments on record, e. g., the following with CO, production in 

 dextrose solution in which CaCOg is in excess. This dextrose solution 

 is inoculated with soil. The one series contained some potassium phos- 



Fig. 15. Ammonid Production in Peptone Solution. 



