1923] 



KLOTZ — NITROGEN METABOLISM IN FUNGI 



303 



duction of nitrates to nitrites by the various fungi. The solution 

 was tested qualitatively with Trommsdorfs reagent and meta- 

 phenylendiamin. Nitrite was considered an intermediate product 

 in nitrate assimilation. Ammonia, however, evolving from 

 further reduction could not be demonstrated. Because am- 

 monia is a product of autolysis he warns against the error of 

 interpreting the presence of this as an indication of further re- 

 duction, as was done by Schlosing and Miintz (78), Hagem ('10), 



and others. 



Ritter ('14) grew Aspergillus niger on a medium containing 

 10 per cent cane sugar as the carbon source, and NH 4 NOi in 

 concentrations of 0.4, 0.8, 1.6 per cent as the source of N. After 

 incubation the mat was filtered off, washed, and dried, and on the 

 filtrate and washings, made to volume, were determined NH, by 

 distillation with MgO, RNO, by reduction with Zn and Fe, and 

 acidity in terms of 0. 1 AT NaOH. The acidity was also calculated 

 from the difference between the amounts of RNOi and NH t 

 found in the culture. He found that the extent of the acidity 

 attained in 3 to 4 days was such as to render further development 

 of the fungus impossible, as shown by the dry weights. The 

 quantity of acid produced in the media containing 0.8 and 1.6 

 per cent NH«NO, approached 0.1 normality but in those having 

 only 0.42 per cent it reached only 0.04 A" in 2 days and fell to 

 0.002 A in 8 days, indicating, he thought, a utilization of HNOt 

 by the fungus. Parallel experiments with the N sources, am- 

 monium tartrate, and HNO» in the strength equivalent to 11.35 

 mg. of N per culture, showed that the free acid after 6 days of 

 incubation at 32° C. was superior for Aspergillus niger and a 



Penicillium. 



Hagem ('10) investigated many species of Mucor and divided 

 them into 2 classes with respect to their ability to assimilate N 

 from nitrates and nitrites. All forms that were capable of as- 

 similating nitrates could also obtain their N from the NOj ion. 

 Because of this and because all thrived on N supplied as am- 

 monium salts, and because in all cultures ammonia accumulated 

 in the culture medium, he assumed that in the process of nitrate 

 assimilation nitrates are reduced to nitrites and further to am- 

 monia. Species thriving on sucrose could not utilize this sugar 



