Chap t e r 9 



The Genus Micromonospora 



The genus Micromonospora is character- 

 ized by the production in nutrienl media of a 

 well developed substrate mycelium, 0.2 to 

 0.6 n in diameter, partly penetrating into 

 the medium. The substrate or vegetative 

 hyphae arc straight or curved, branching, 

 without cross walls. Aerial mycelium is not 

 formed at all or only in a rudimentary, non- 

 sporulating form, when the hyphae arise 

 upward directly from the substrate myce- 

 lium. 



Multiplication occurs by means of frag- 

 ments of mycelium and special spores formed 

 singly. A swelling takes place at the end of 

 the sporophore; later the swelling is sepa- 

 rated by a cross wall, giving rise to spherical, 

 oval, or oblong spores, 1.0 to 1.5 by 0.8 to 

 1.2 m- The sporophores are often branched, 

 each branch forming a spore at the end, 

 giving rise to a grape-like bunch of spores. 

 These germinate in a manner similar to the 

 spores of Streptomyces. The mycelium and 

 >poivs are gram-positive, not acid-fast (Fig. 

 52). 



The colonies of Micromonospora are simi- 

 lar to those of Streptomyces. They are com- 

 pact, leathery, smooth or lichenoid, raised or 

 flat. They are frequently colored red or 

 orange or yellow, occasionally brown or green 

 To almost black or bine. The pigments, ex- 

 cept the dark brown, are not dissolved into 

 the medium. 



In characterizing species of Micromono- 

 spora, T'ao Bo and Potter (1960) considered 

 morphological properties as primary criteria 

 for identification of the organisms. The 



important physiological characteristics in- 

 cluded the disintegration of cellulose, in- 

 version of sucrose, and the reduction of 

 nitrate. The investigators emphasized that 

 the color of the growth and the form of the 

 colony could not serve as basic characteris- 

 tics. Certain strains may show different 

 colors for the mass of growth and for the 

 spores. Reproducibility of colony color for a 

 given organism could not be obtained on the 

 same medium. The color itself was not con- 

 sistent, varying through every shade of yel- 

 low, orange, pink, red, and brown. Many 

 species gave more than one colonial form. 

 The large spores of M. globosa were very 

 helpful in differentiating it from .1/. fusca or 

 M. chalcea. 



Micromonospora species are aerobic or 

 anaerobic, and mesophilic. They grow- 

 readily at 25-40°C. Thermal death point of 

 the mycelium is 70°C in 2 to 5 minutes; 

 spores resist 80°C for 1 to 5 minutes. They 

 utilize various carbon and nitrogen sources, 

 both organic and inorganic (Fig. 5:!). 



The type Species is Micromonospora chair, a 



(Foulerton) 0rskov. 



The genus Micromonospora comprises nine 

 species, which can be classified as follows: 



Classification of the genus Micromonospora 



A. Aerobic. 



I. Sporophores lnn^- 



1. Sporophores showing Hi lie branching, 

 a. No aerial mycelium. 



'_'. Micromonospora chalcea 

 1). Rudimentary aerial mycelium. 

 (i. Micromonospora gallica 



