16 SELMAN A. WAKSMAN 



isms or to its transformation into other substances, such as 

 ammonia. It will be noticed that the organisms that made 

 the poorest growth on certain amino acids, used the least 

 nitrogen, while those that made a good growth caused a good 

 deal of the amino-nitrogen to disappear from the medium. For 

 example, in the case of asparagin, the medium containing orig- 

 inally 3.99 mgm. NH 2 -N in 10 cc, A. asteroides with a faint 

 growth caused a decrease in thirty days to 3.92 and in sixty 

 days to 3.86; while A. griseus with a very good growth, changed 

 it in fifteen days to 1.30, which seems to have accompanied the 

 maximum growth, since in thirty days there was a slight increase 

 in the amino nitrogen content, namely 1.48, which may be due 

 either to an individual variability of the cultures or to some 

 autolysis that might have set in. 



The production of ammonia does not seem to be a character- 

 istic property of this group of organisms, as was already pointed 

 out elsewhere (Waksman and Curtis, 1916). It is possible that 

 ammonia does not enter as a necessary step in their metabolism, 

 as some investigators claim for other microorganisms and that it 

 is not formed in large quantities as a waste product of metab- 

 olism, although we find individual variations between the 

 different species and with different substrata. These organisms 

 seem to assimilate the amino acids directly or indirectly, but not 

 necessarily only after reduction to ammonia. The question of 

 the function of ammonia as a protein split product in the metab- 

 olism of molds has been already discussed by the writer else- 

 where (Waksman, 1918). It need only be pointed out here that 

 the actinomycetes and molds seem to split the proteins with 

 different results; while most of the latter reduce the proteins to 

 ammonia very quickly and allow its accumulation in the me- 

 dium, the former seem to split the proteins chiefly to the amino 

 acid stage and only to a limited extent to ammonia. Most 

 ammonia was produced from the peptone and asparagin, least 

 from the egg-albumin and leucin. 



The change in the hydrogen-ion concentration of the media 

 are reported in the paper following this one. 



