METABOLISM OF ACTINOMYCETES 15 



A. asteroides splits proteins and uses amino acids only to a 

 very limited extent, although it produces an abundant growth 

 on certain inorganic media (particularly with glucose as a source 

 of carbon). Certain organisms, such as A. verne, using only 

 small quantities of amino acids when grown on amino-acid- 

 containing media, allow a large accumulation of amino-nitrogen- 

 rich substances when grown on protein containing media, show- 

 ing that there is no necessary correlation between the amount of 

 growth and the protein split. 



The production of amino acids and other amino-nitrogen-rich 

 substances is not a waste resulting from the growth of the organ- 

 isms, but is a definite step in the metabolism of the organisms, 

 since in many cases these substances do not accumulate in the 

 medium, but tend to decrease, either due to their transforma- 

 tion into other substances, such as ammonia (which was not the 

 case) , or to their assimilation as such or as transformation prod- 

 ucts, by the organism, as indicated by the increase in growth. 



Fibrin, casein, egg-albumin and peptone allow a very good 

 growth of nearly all the actinomycetes studied, the second and 

 the fourth leading, as to the actual amount of growth. Small 

 quantities of amino-nitrogen are present in the proteins; these 

 are equivalent to one-half of the lysin nitrogen, as shown by 

 Van Slyke and Birchard (1914). Some organisms seem to start 

 using this lysin nitrogen at first, particularly the species which 

 are weak proteolytically, such as A. asteroides on the casein 

 medium. In most cases, the accumulation of amino-nitrogen 

 becomes prominent only when the organism has made most of 

 its growth. This may be due either to the fact that during the 

 period of its active growth, the organism uses all or most of the 

 amino-nitrogen that it can split, or to the fact that the splitting 

 is accomplished by means of a proteolytic enzyme, which is 

 absent in the early stages of growth or present in only minute 

 quantities. 



The amino acids studied, particularly glycocoll, were also well 

 utilized by most organisms. The progress of growth can also be 

 followed by the decrease in the amino-nitrogen present in the 

 medium, either due to its assimilation by the growing organ- 



