Chaffer 11 



IDENTIFICATION AND DESCRIPTIONS 

 OF IMPORTANT TYPES 



Classification of Actinomycetales: — The following classification of 

 the actinomycetes is based entirely upon material included in Bergey's 

 Manual of Determinative Bacteriology (34). For more detailed infor- 

 mation as well as for literature references, the reader is referred to that 

 Manual. 



Order Actinomycetales 



Organisms forming elongated, usually filamentous cells, with defi- 

 nite tendency to branching; hyphae not exceeding 1.5[x in diameter, 

 mostly about \\i or less. Usually producing a characteristic' branched 

 mycelium. Multiply by means of special spores, as well as by oidio- 

 spores or by conidia. The special spores are formed by fragmentation of 

 the plasma within the spore-bearing hyphae, the latter being straight or 

 spiral-shaped. The oidiospores are formed by segmentation, or by sim- 

 ple division of hyphae by means of transverse walls, in a manner similar 

 to the formation of oidia among the true fungi. The conidia are pro- 

 duced singly, at the end of special, simple or branching conidiophores. 

 They grow readily on artificial media and form well developed colonies. 

 The surface of the colony may become covered with aerial mycelium. 

 Some of the organisms are colorless or white, whereas others form a 

 variety of pigments. They are either saprophytic or parasitic. In rela- 

 tion to temperature, most are mesophilic, though some are thermophilic. 

 Certain forms are capable of growing at low oxygen tension. 



Key to the families of order Actinomycetales:— 



A. Mycelium rudimentary or absent, no spores formed— Family Mycohacteriaceae. 



I. Acid-fast organisms Mycohacteriwn. 



B. True mycelium produced: 



I. Vegetative mycelium divided by segmentation into bacillary or coccoid 

 elements Family Actinomycetaceae. 



1. Anaerobic or microaerophilic, usually parasitic, non-acid-fast 



Actinomyces. 

 Type species— Acfinowyces hovis. 



2. Aerobic, partially acid-fast or non-acid-fast Nocardin. 



Type species— Nocard/a farcinica. 

 II. Vegetative mycelium normally remaining undivided— Family 



Stre^tomycetaceae. 



