IS(»I,AIM(>N. 1I)|;N1I1-|( A lloN, ( l l/ll\ All( »N , AND i'lM ;SI ;i!\ AI'lo.X 



lU 



Fkure 12. Cross-section of a typical actinoinvccte colony on an a^jar incdiuin 



of characterization and classification, one 

 must list the structure and subsequent 

 changes in the substrate or vegetative myce- 

 lium, the production and nature of the aerial 

 mycelium, the nature of the sporulating 

 branches or sporophores, and the size, shape, 

 and surface of the spores. 



Among the physiological and cultural 

 properties essential for characterization of 

 actinomycetes, pigmentation of the sub- 

 strate growth and of the aerial mycelium is 

 most important; the formation of soluble 

 l)igments, both in synthetic and in organic 

 media, is also significant. Among the other 

 properties that make possible proper species 

 identification of the organisms are hydroly- 

 sis of proteins including gelatin and milk 

 casein, hydrolysis of starch, in\'ersion of 

 sucrose, digestion of cellulose, and formation 

 of specific antibiotics. The utilization of 

 sugars and related compounds, with and 

 without the formation of acids, can supply 

 additional information for species dif!"eren- 

 tiation. The antagonistic activities and the 

 ability to produce antibiotics have recently 

 come into popular use for the characteriza- 

 tion of specific organisms. The sensitivity of 

 actinom^'cetes to specific phages and to 

 known antibiotics is also of consideral)l(> im- 

 portance in establishing specific differences. 

 Among the other supplementary character- 



Fkuke I'.i. (icrminationof actiiioniycctc spores 

 (Reproduced from: L\ct<ke, H. MorplwIo</ic imd Bi- 

 ologic der Slrahlenpilze. Verlag von Ciohri'ider 

 Borntraeger, Leipzig, 1921, p. 86, 87). 



