Chapter 6 



Series and Species of the Genus 

 Streptomyces 



The genus Streptomyces was created in 

 L943, to separate certain aerial mycelium- 

 producing actinomycetes from the rest of 

 the order Actinomycetales. Although there 

 is considerable overlapping between species 

 placed in this genus and those of Nocardia 

 and Mime of the thermophilic groups, there 

 are certain important properties that may 

 be said to characterize this genus, thus 

 separating it, if not for any other reason 

 than thai of convenience, from the other-. 



The major important characteristic prop- 

 erties that distinguish the genus Streptomy- 

 ces from the others can he briefly summar- 

 ized as follows: 



1. A more or less branched, nonseptate, 

 substrate or vegetative mycelium (stromal 

 is produced. 



2. Growth takes place either on the sur- 

 face of agar or gelatin media or penetrates 

 deep into the medium, forming a compact, 

 often leathery mass, designated as a colony. 



3. During growth in stationary liquid 

 media, no turbidity is produced except on 

 lysis; the masses of growth appear as clumps 

 or compad masses. 



4. The surface colony gradually becomes 

 covered with an aerial mycelium, though 

 this occasionally may not occur. 



5. The aerial mycelium produce.- sporo- 

 genous hyphae or fruiting bodies, which are 

 straight, or in the form of tufts, or curved, 

 spiral-shaped, or verticillate. 



(i. The sporophores carry chains <>l single- 

 celled spores (or conidia), which vary in 

 shape from spherical to oblong or cylindrical, 

 and also in surface appearance when viewed 

 with the electron microscope. 



7. The vegetative growth, the aerial my- 

 celium, and the spore- < u masse frequently 

 are colored in a characteristic manner; the 

 color may also dissolve into the medium, 

 producing a "soluble pigment." 



8. The species are aerobic and meso- 

 philic, nonacid-fast and gram-positive. 



The genus Streptomyces comprise-, by tar. 

 the largesl number of species of actinomy- 

 cetes now known to occur in nature. The 

 various specie- belonging to this genus differ 

 greatly in their morphological, cultural, 

 physiological, and biochemical properties. 

 They include the majority of antibiotic- 

 producing actinomycetes. The growing eco- 

 nomic importance of these organisms has 

 tended to increase the need tni- the separa- 

 tion of the "-enus into groups, each of which 

 would contain one or more species. This 

 need ha- recently been further emphasized 

 by the creation of numerous additional spe- 

 cies. 



The color of the aerial and substrate my- 

 celium, the morphology of sporophores, mid 

 the formation of melanin pigments have 

 been largely used for the separation of the 

 genus Streptomyces into series and species. 

 For the supplementary characterizati f 



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