-358 



Mr. H. S. Fremlin. 



[Feb. 23, 



Liquid Media containing Organic Matter. 



I made a series of experiments with "ammonia solutions" contain- 

 ing peptone beef broth, Witte's powdered peptone, and urea. 



Beef Broth. 



This was added in quantities varying from 1 in 11000 to 10 in 100. 



Cultures of nitroso-bacteria grew well when inoculated from 

 inorganic solutions into the lower percentages of beef broth, and on 

 transferring them to higher percentages they were able to continue 

 their nitrification. If cultures of nitroso-bacteria were taken from 

 inorganic solutions and placed directly into solutions containing beef 

 broth to the extent of 1 in 1000 they failed to show oxidation. 



Peptone. 



This was used in solutions containing 1 in 11000 and 1 in 5000. 

 The nitroso-bacterium was able to grow in these solutions ; its 

 development being satisfactory, as shown by the formation of nitrite. 



Urea. 



" Ammonia solutions " were prepared which contained from 1 in 

 11000 to 1 in 1000 of urea. 



The nitroso-bacterium although developing in the presence of small 

 quantities of urea failed to do so when the solution contained as much 

 .as 1 in 1000. 



The above experiments show that the nitroso-bacteria can grow in 

 the presence of organic matter. The addition of small quantities of 

 -organic matter to ammonia solution containing the nitroso-bacterium 

 does not apparently check the formation of the nitrous acid. 



The addition of larger percentages of organic matter to " ammonia 

 solutions " does tend to check and finally stop the action of these 

 bacteria if they are introduced directly from soil, or from inorganic 

 media. 



The experiments also show that, where nitroso-bacteria have oxidised 

 ammonia in solutions which contain small quantities of organic matter, 

 they are able to continue this work when transferred to solutions of 

 ■ammonia containing amounts of organic matter that entirely arrest 

 their oxidising action when they are transferred thereto direct from 

 inorganic solutions. 



