CLASSIFICATION OF THE ACTINOMYCETES 29 



b. Weakly proteolytic. 



a 1 . Produce a brown substance on synthetic media. 



Streptomyces calif ornicus 

 b 1 . Do not produce any brown substance on synthetic media. 

 a 2 . Grow at an acid reaction. 



Streptomyces acidophilus 

 b 2 . Grow at a neutral reaction. 

 Streptomyces albidus 

 II. Aerial mycelium produced in concentric rings. 

 Streptomyces annulatus 

 B. Aerial mycelium yellowish . 



Streptomyces albidoflavus 

 Various other species belonging to the genus Streptomyces can be classified 

 into groups, on the basis of their morphology (whorl-producers), physiology 

 (pigment-producers), activity (pathogenicity), or utilization (antibiotic- 

 producers). It is sufficient to mention particularly the very large Strepto- 

 myces scabies group, comprising cultures or species producing potato scab; 

 the Streptomyces coelicolor group, producing red and blue or violet pigments 

 on synthetic media; the Streptomyces viridis group, producing green pig- 

 ments; the Streptomyces globisporus group. 



The Genus Nocardia 



Nocardias represent a group of organisms which include both parasites 

 and saprophytes. Their relationship to the mycobacteria, on the one hand, 

 and to the streptomycetes, on the other, has already been indicated. The 

 fact that a culture has been isolated from a lesion in man or animal is no 

 proof that it is the causative agent of the particular infection; it may be a 

 secondary agent or a member of a mixed infection. 



Several systems of classification have been suggested for this group of 

 organisms. Of these, one by Krassilnikov and the other by Waksman and 

 Henrici are considered here in detail. 



Since nocardias occupy, so far, only a secondary place as producers of 

 antibiotics, no detailed descriptions of groups are presented. 



Classification System of Krassilnikov 

 A. Cultures colorless, some excreting a brown substance into the medium. 

 I. Aerial mycelium and spore-bearing hyphae produced in culture 

 media. 



1. Substrate and aerial mycelium occasionally forming septae; the 

 hyphae break up into long rods, 15-30 /x; spherical bodies not 

 formed. 



a. Saprophytes, found on dead substrate. 



Nocardia actinoides /S> ^boS ^^-f 



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 MASS. A 



