892 MANUAL OF DETERMINATIVE BACTERIOLOGY 



FAMILY II. ACTINOMYCETACEAE BUCHANAN.* 



(Jour. Bact., 3, 1918, 403.) 



Mycelium is non-septate during the early stages of growth but later may become 

 septate and break up into short segments, rod -shaped or spherical in shape, or the 

 mycelium may remain non-septate and produce spores on aerial hyphae. The or- 

 ganisms in culture media are either colorless or produce various pigments. Some 

 species are partially acid-fast. This family is distinguished from the previous one 

 by the formation of a true mycelium. As compared with the next family, it is charac- 

 terized by the manner of spore formation. 



Key to the genera of family Actinomycetaceae. 



I. Obligate aerobic. The colonies are bacteria-like in nature, smooth, rough or 

 folded, of a soft to a dough-like consistency, sometimes compact and leathery 

 in young stages. Most forms do not produce any aerial mycelium; a few pro- 

 duce a limited mycelium, the branches of which also break up into oidiospores 

 or segmentation spores. Some species are partially acid-fast. 

 Genus I. Nocardia, p. 892. 

 II. Anaerobic or microaerophilic, parasitic; non-acid -fast, non-proteolytic and non- 

 diastatic. 



Genus II. Actinomyces, p. 925. 



Genus I. Nocardia Trevisan. 



(Trevisan, I generi e le specie delle Batteriacee, 1889, 9; Actinomyces Gasperini, 

 Cent. f. Bakt., 15, 1894, 684 and Atti dell' XI congresso med. internaz. Roma, 6, 

 1895, 82; not Actinomyces Harz, Jahresber. d. Miinch. Thierarzneischule for 1877- 

 1878, 1879, 125; Actitiobacter i2im Haas , Cent. f. Bakt., I Abt., Orig., 40, 1906, 180; Sam- 

 pietro, Ann. d'Igiene, Roma, 18, 1908, 331; Actinococcus Beijerinck, Folio Microbiol., 

 Delft, 3, 1914, 196; not Actinococcus Kiitzing, Species Algarum, 1849; Brevistrepto- 

 thrix Lignieres, Ann. Parasit. hum. et comp., 2, 1924, 1 ; Asteroides Puntoni and Leo- 

 nardi. Boll, e Atti d. R. Accad. Med., 67, 1935, 90; Proactinomyces Jensen, Proc. Linn. 

 Soc. New So. Wales, 56, 1931, 345.) Named for Prof. E. Nocard who first described 

 the type species. 



Slender filaments or rods, frequently swollen and occasionally branched, forming a 

 mycelium which after reaching a certain size assumes the appearance of bacterium- 

 like growths. Shorter rods and coccoid forms are found in older cultures. Conidia 

 not formed. Stain readily, occasionally showing a slight degree of acid-fastness. 

 Non -motile. No endospores. Aerobic. Gram-positive. The colonies are similar 

 in gross appearance to those of the genus Mycobacterium. Paraffin, phenol and 

 m-cresol are frequently utilized as a source of energy. 



In their earlj- stages of growth on culture media (liquid or solid), the structure of 

 nocardias is similar to that of actinomyces in that they form a tj'pical mycelium 

 hyphae branch abundantly, the branching being true. The diameters of the hyphae 

 vary between 0.5 and 1 micron, usually 0.7 to 0.8 micron, according to the species. 

 The mycelium is not septate. However, the further development of nocardias differs 

 sharply from that of actinomyces : the filaments soon form transverse walls and the 

 whole mycelium breaks up into regularly cylindrical short cells, then into coccoid 



* Completely revised by Prof. S. A. Waksman, New Jersey E.xperiment Station, 

 New Brunswick, New Jersey and Prof. A. T. Henrici, University of Minnesota, 

 Minneapolis, Minnesota, May, 1943. 



