PROTEOLYTIC ACTIVITIES OF SOIL MICROORGANISMS 483 



of ammonia as a waste product ; it is characteristic that these two 

 organisms are very rapid growers and are closely allied. At the 

 other extreme we find organisms, such as the two strains of 

 Act. violaceus-ruher , Act. penicilloides, and B. mycoides, which, 

 without producing a very strong growth upon the medium used, 

 showed a large accumulation of amino nitrogen containing com- 

 pounds with the production of a rather small quantity of am- 

 monia. Organisms, like Citr. glaber and P. chrysogenum, seem 

 to allow an accumulation of amino nitrogen and ammonia, but 

 neither in a great excess. 



An experiment was started using A. niger, for the purpose of 

 testing the influence of sugar upon the formation of decomposi- 

 tion products from proteins. Czapek's solution containing 2 

 per cent peptone in place of the NaNOs, without the sugar, was 

 divided into two portions: to one half 3 per cent of cane sugar 

 was added and the second half was left without sugar, so that 

 the peptone would have to supply to the organism both nitrogen 

 and carbon. These solutions were distributed in 100 cc. portions 

 in 200 cc. Erlenmeyer flasks, sterihzed and inoculated with an 

 approxunately equal number of spores, then incubated at 28°C. 

 At the end of every twenty-four hours one flask from each set 

 was taken out from the incubator for the determination of amino 

 and ammonia nitrogen. From the ninth day till the end of the 

 experiment, after the ammonia had been expelled by the action 

 of Na2C03, the aeration was further continued upon the addition 

 of NaOH. Two grams of Na2C03 were added to 50 cc. of medium 

 and aeration continued for three hours. After fhat period 1 

 to 2 grams of NaOH and 10 grams of NaCl were also added to 

 the medium, and aeration continued further, for one hour, into a 

 fresh quantity of standard 0.1 n H2SO4. The data obtained from 

 these determinations are given in table 3. The second quantity 

 of ammonia is either due to the decomposition of magnesium- 

 ammonium-phosphate crystals that might have been formed in 

 the medium and were not decomposed by the Na2C03, or to the 

 decomposition of the amide nitrogen present in the medium, as 

 was pointed out before. Both of these may account for the 

 large quantities of ammonia expelled by the NaOH; it might be 



