CLASSIFICATION OF THE ACTINOMYECTES 35 



10. Growth yellowish to golden brown. 



42. Nocardia fordii 



11. Growth yellow to reddish brown; soluble pigment brown to red. 



43. Nocardia kuroishi 



The Genus Micromonospora 



The genus Micromonospora is characterized by the production in nutrient 

 media of a well-developed vegetative mycelium, 0.3-0.6 n in diameter, 

 partly penetrating into the medium. The vegetative hyphae are straight or 

 curved, branching, without cross walls. Aerial mycelium is not produced 

 at all or only in rudimentary, nonsporulating form, the hyphae arising 

 upward from vegetative mycelium. 



Multiplication takes place by means of fragments of mycelium and special 

 conidia produced singly, at the ends of sporophores arising upward from 

 substrate mycelium. The sporophore produces a swelling at the end, and 

 later the swelling is separated by a cross wall giving rise to spherical, oval, 

 or oblong conidia 1.0-1.5 by 0.8-1.2 n. The conidiophores are often 

 branched, each branch forming a conidium at the end, giving rise to a 

 grape-like bunch of conidia. The conidia germinate in a manner similar to 

 the spores of Streptomyces. The mycelium and conidia are gram-positive, 

 non-acid-fast. 



The colonies are similar to those of Streptomyces. They are compact, 

 leathery, smooth or lichnoid, raised or flat. They are frequently colored red 

 or orange or yellow, occasionally brown or green to almost black or blue. 

 The pigments, except the dark brown, are not dissolved into the medium. 



They are aerobic and grow readily at 35-37°C. 



They utilize various carbon and nitrogen sources, both organic and in- 

 organic. 



Two systems of classification of this genus are presented here. 



Classification System of Krassilnikov 



A. Sporophores long, branched. 

 I. Spores spherical. 



1. Spores singular, or sporophores with little branching. 



Micromonospora chalceae 



2. Spores produced on numerous branches. 



a. Cultures colorless; spores appear in mass as brown-pig- 

 mented Micromonospora globosa 



b. Cultures pigmented. 



a 1 . Cultures dark green; spores blue. 

 Micromonospora coerulea 



