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THE A.CTINOMYCETES, Vol. II 



gelatin liquefaction, coagulation and pep- 

 tonization of milk, and hemolysis of blood; 

 utilization of carbon compounds; antagonis- 

 tic properties and formation of antibiotics; 

 effect of temperature, aeration, and reaction 

 upon growth; formation of specific enzymes, 

 such as oxidase, lipase, invertase, diastase, 

 mannase and protease; reduction of nitrate, 

 and formation of H 2 S. There is no sharp line 

 of demarcation between cultural and physio- 

 logical properties, on the one hand, and be- 

 tween physiological and biochemical activi- 

 ties, on the other. 



4. Ecology. The ability of the organism to 

 cause animal or plant diseases, and its occur- 

 rence in a natural environment are important 

 characteristics. 



5. Supplementary characteristics. Addi- 

 tional characteristics that may be utilized 

 for descriptive purposes include: (a) sero- 

 logical reactions, (b) phage sensitivity, and 

 (c) sensitivity to specific antibiotics. 



In describing the various species, one has 

 to depend frequently upon the information 

 supplied in published reports, since type 

 cultures often are not available. Where the 

 desired information is lacking or where the 

 description, for various reasons, is inade- 

 quate, the species may be placed in the list 

 of incompletely described forms. 



Recently there has been a tendency to 

 overlook earlier described species, and to 

 emphasize and often give new names to 

 newly isolated cultures. One cannot con- 

 demn this tendency too strongly. While, in 

 most cases, it is difficult to establish synon- 

 ymy because of a lack of type cultures or a 

 possible change in such cultures upon pro- 

 longed cultivation on artificial media, every 

 effort must be made to give credit to the 

 earlier investigator. One has no patience, 

 therefore, with those attempts to set aside, 

 willfully or unwillfully, older descriptions 

 or to consider such organisms as varieties of 

 newly isolated and newly named cultures. 



When n culture is freshly isolated, a study 



should be made both of its position in a 

 particular group in the genus and of its 

 classification as a species. Only by a com- 

 bination of properties described under both 

 can one determine the identity of the new 

 culture. Obviously, no conclusions should be 

 drawn that such a culture represents a new 

 species merely on the basis of certain super- 

 ficial observations, such as a delay in coag- 

 ulation and peptonization of milk or in 

 liquefaction of gelatin, or because of a differ- 

 ence in the intensity of coloration of the 

 potato plug, or in the shade of pigmentation 

 of growth on a particular medium, or even 

 in the degree of curvature of the sporophores. 

 Any attempt to create new species on the 

 b;ois of such minor variations must be con- 

 sidered both unscientific and confusing. The 

 tests must be repeated again and again to 

 confirm the recorded observations. 



The need for a knowledge of the exact 

 composition of the media used for descrip- 

 tive purposes can hardly be overemphasized. 

 Some species show their most characteristic 

 property upon only one particular medium, 

 and unless such a medium is used, the prop- 

 erties of a new isolate can easily be over- 

 looked. S. fradiae, for example, shows the 

 characteristic color (seashell-pink) of its 

 aerial mycelium upon potato-starch agar. 

 Certain synthetic agar media, notably 

 nitrate-sucrose, glucose-asparagine, and cal- 

 cium malate, are among those which alone 

 bring out characteristic properties of certain 

 other species. Growth on potato is quite 

 characteristic, although the variety of the 

 potato, the manner of crop fertilization, and 

 other factors may influence the nature of the 

 growth of the organism and pigment formed. 



In view of the great interest at the present 

 time in the screening programs for antibi- 

 otics, when literally many thousands of cul- 

 tures are being isolated and tested, there is 

 naturally a tendency on the part of some 

 investigators to consider the ability of a 

 particular culture to form a specific anti- 



