METABOLISM OF ACTINOMYCETES 11 



The chemicals used throughout the work were chemically pure, 

 usually Kahlbaum's or Merck's. The casein was purified by the 

 method of Hammarsten. 



In glancing through table 1, one can readily see that most of 

 the organic nitrogenous substances both proteins and amino 

 acids, form a readily available source of nitrogen for the actino- 

 mycetes; while the amides, namely acetamide and urea used in 

 this investigation and the inorganic nitrogenous substances form 

 a much poorer source of nitrogen for this group of microorgan- 

 isms. Nearly all the organisms studied, with very few excep- 

 tions, notably A. asteroides, made a fair to excellent growth upon 

 the proteins, but grew rather poorly on the amides and on the 

 inorganic nitrogenous substances. The quantity of growth is not 

 absolute, but since the record was made by the same investigator 

 under as nearly identical conditions as possible, it lends itself to 

 comparison. The ammonium salts, both the sulfate and car- 

 bonate, were found to be the poorest sources of nitrogen under 

 the conditions of the experiment and for the organisms studied; 

 only A. aureus and A. ruber made a fair growth on these sub- 

 stances, as the only source of nitrogen, while all the others pro- 

 duced no growth or hardly any noticeable growth at all. This 

 held true when these substances were studied in solution; a 

 better growth might have been obtained on solid media. This 

 fact has been brought out by Krainsky (1914), who stated that, 

 with NH4NO3 as a source of nitrogen, the nitrate radical was 

 used up in a comparatively short time, while the ammonia per- 

 sisted for a long period. This relative inability of the actino- 

 mycetes to use ammonia compounds as a source of nitrogen may 

 help to explain the fact that in their action upon proteins and 

 amino acids the actinomycetes produce at first very little am- 

 monia, especially when compared in this respect with the bac- 

 teria and molds. This brings up the whole question of the 

 relative nitrogen metabolism of these groups of microorganisms, 

 which will be taken up later. 



Nitrates are readily used as a source of nitrogen, although the 

 actual amount of growth, particularly on liquid media, is far 

 inferior for most organisms to that produced on the proteins and 



