490 SELMAN A. WAKSMAN 



fungi than of the bacteria; and the fungi, as was shown elsewhere 

 (Waksman, 1916), produce as a group a great deal naore anunonia 

 than do the other microorganisms under the same conditions. 

 Thus we see that by producing a slight change in the environ- 

 mental conditions, we not only change the conditions for micro- 

 organic activities, but stimulate a change in the active soil flora. 

 The influence of any one factor is so important in controlhng 

 the amount of ammonia accumulated in the medium, that the 

 ammonification studies, which occupy such an important place 

 in many bacteriological investigations, particularly with soils, 

 will have to be carefully revised. The very study of ammoni- 

 fication seems to be of doubtful importance, firstly due to the 

 fact that all the controlling factors can hardly be taken into 

 consideration in any one experiment (this refers particularly 

 to mixtures of microorganisms) ; secondly, because it has not been 

 proven as yet that ammonia is an end product in protein metab- 

 olism and under exactly what conditions it is formed as a waste 

 product; thirdly, the ammonia produced by mixtures of micro- 

 organisms will be differently affected by different conditions 

 which do not affect alike the different groups of microorganisms; 

 and fourthly, if the production of ammonia by microorganisms 

 is studied, it should not be studied by itself but in connection 

 with the other activities of the microorganisms. 



SUMMARY 



1. Different organisms behave differently in their power to 

 attack proteins and in the production of amino nitrogen and 

 ammonia. 



2. Most of the molds which grow very rapidly, as manifested 

 by the increase in weight of their mycelium, allow a small amount 

 of amino nitrogen to accumulate in the medium, while the 

 amount of ammonia accumulated increases with the period of 

 incubation. 



3. Certain molds, particularly the slower growing ones, the 

 actinomyces studied, and B. mycoides favor a large accumulation 



