114 



THE ACTIXOMYCETES, Vol. I 



given organism is discussed, whenever its 

 mode of nutrition and growth characteristics 

 are examined, and its biosynthetic reactions 

 analyzed, it is essential to keep in mind that 

 the conclusions reached hold true for a given 

 environment and for a given set of nutri- 

 tional conditions. Changing the environ- 

 ment, as by raising or lowering the tempera- 

 ture of growth, by modifying the conditions 

 of aeration, or by changing the reaction, or 

 changing the composition of the medium, as 

 by introducing different nutrients and in 

 different concentrations, will change the 

 growth characteristics and metabolic pat- 

 tern of the particular organism. Not the 

 least important among these considerations 

 is the recognition of the strain specificity of 

 an organism, whereby certain reactions are 

 limited not to a genus or even a species, but 

 to a certain race or strain. 



The metabolism of an organism represents 

 a special phase of its physiology. To com- 

 prehend it, we must understand the food- 

 stuffs necessary for the maintenance of its 

 growth and activities; the manner of obtain- 

 ing the required energy ; the products formed 

 as a result of such activities ; and the various 

 intermediary reactions through which the 

 nutrients pass when they are used for cell 

 synthesis. Normal metabolism of an or- 

 ganism, when it grows under natural condi- 

 tions similar to those it finds in a natural 

 environment, is often differentiated from ab- 

 normal metabolism, when the growth of an 

 organism is made to deviate from the nat- 

 ural path of life to which it has been accus- 

 tomed. Such a deviation occurs in virtually 

 all methods used for growing microorgan- 

 isms on artificial media and under controlled 

 conditions. It is only seldom that a microbe 

 grows in nature in a pure culture. Once it 

 has been isolated and made to grow in an 

 artificial substrate, its metabolism may be 

 considerably modified. 



Among the factors influencing the metab- 

 olism of microorganisms, the following ai"e 



most significant: 



1. The nature of the energy sources 



2. The nature and concentration of the 

 nutrients used for cell synthesis, especially 

 carbon and nitrogen compounds, mineral re- 

 quirements, and the need for certain rare 

 elements. 



3. The need for specific growth-promoting 

 substances or vitamins. 



4. The particular oxygen tension of the 

 medium. 



5. Optimum temperature and reaction. 



6. Influence of other organisms, with the 

 resultant associative and antagonistic effects 

 exerted by them and upon them. 



These factors influence the extent of 

 growth of the microbial cell, its chemical 

 composition, and the nature and concentra- 

 tion of specific metabolic products produced. 



Metabolism of Actinoniycetes 



Any comprehensive discussion of the met- 

 abolic activities of a group of organisms 

 must consider their utilization of various nu- 

 trients, decomposition of these nutrients into 

 simpler compounds, the various mecha- 

 nisms of transformation of these nutrients, 

 involving those concerned with both break- 

 down and synthesis, formation of waste 

 products, and a variety of other reactions 

 involved in the life of living cells. 



In the very early studies on the growth of 

 actinoniycetes, it was found that these or- 

 ganisms vary greatly in their mitrient re- 

 quirements. Some were found able to con- 

 sume simple elements and compounds; 

 others required complex organic materials. 

 Considerable adaptation to various nutri- 

 ents also w^as observed. The amount of cell 

 material synthesized depended on the avail- 

 ability of the nutrients and on the effect of 

 the accumulated products. 



Beijerinck first studied an organism he 

 considered to be a bacillus {B. oligocarbo- 

 philus), later found to be an actinomycete, 

 that was capa))k' of deriving its carbon and 



