FAMILY ACTINOMYCETACEAE 893 



cells. On fresh culture media, the coccoid cells germinate into mycelia. The whole 

 cycle in the development of nocardias continues for 2 to 7 days. Most frequently the 

 coccoid cells are formed on the third to fifth day, but in certain species (e.g., Nocardia 

 rubra) they can be found on the second day. 



Numerous chlamydospores may be found in older cultures of nocardias. They are 

 formed in the same way as the chlamydospores in true fungi: the plasma inside the 

 filaments of the nn'celium condenses into elongated portions. In older cultures of 

 nocardias many coccoid cells are changed into resistant cells. The latter are larger 

 than the vegetative coccoid cells ; the plasma of these cells is thicker than the plasma 

 of vegetative cells ; on fresh media they germinate like the spores of actinomyces ; 

 they form 2 to 3 germ tubes. Besides the cells mentioned, numerous involution 

 forms can often be found in older cultures of nocardias ; the cells are thin, regularlj^ 

 cylindrical or coccoid, are often transformed into a series of spherical or elliptical 

 ampules and a club-like form (2 to 3 microns and more) . 



The multiplication of nocardias proceeds by fission and budding; occasionally they 

 form special spores. Budding occurs often. The buds are formed on the lateral 

 surface of the cells ; when they have reached a certain size, they fall off and develop 

 into rod-shaped cells or filaments. The spores are formed by the breaking up of the 

 cell plasm into separate portions usualh' forming 3 to 5 spores ; every portion becomes 

 rounded, covered with a membrane and is transformed into a spore; the membrane 

 of the mother cell dissolves and disappears. The spores germinate in the same way 

 as those of actinomyces. They form germ tubes which develop into a mycelium. 



The colonies of nocardias have a paste-like or mealy consistency and can easily be 

 taken up with a platinum loop ; they spread on glass and occasionally render the broth 

 turbid. The surface colonies are smooth, folded or wrinkled. Typical nocardias 

 never form an aerial mycelium, but there are cultures whose colonies are covered with 

 a thin coating of short aerial hj^phae which break up into cylindrical oidiospores. 



Many species of nocardias form pigments; their colonies are of a blue, violet, red, 

 yellow or green color; more often the cultures are colorless. The color of the cul- 

 ture serves as a stable character. 



. Krassilnikov (Raj- fungi and related organisms, Izd. Acad. Nauk, U.S.S.R., Moscow, 

 1938) divides the genus into two groups: 1. Well developed aerial mycelium; sub- 

 strate mycelium seldom produces cross-walls ; the threads break up into long, thread- 

 like rods; branches of the aerial mycelium produce segmentation spores and oidio- 

 spores; the latter are cjdindrical with sharp ends; no spirals or fruiting branches. 

 This group is the same as group B of Jensen (loc. cit.). 2. Typical forms; mycelium 

 develops only at early stages of growth, then breaks up into rod-shaped and coccoid 

 bodies ; smooth and rough colonies, dough-like consistency ; never form an aerial myce- 

 lium; similar to bacterial colonies ; aerial mycelium may form around colonies. This 

 genus can also be divided, on the basis of acid-fastness, into two groups: Group 1. 

 Partially acid-fast organisms, which are non-proteolytic, non-diastatic and utilize 

 paraffin; usually j^ellow, pink, or orange-red in color. Group 2. Non-acid-fast or- 

 ganisms, which are diastatic, largely proteolytic and do not utilize paraffin; yellow, 

 orange to black in color. 



The type species is Nocardia farcinica Trevisan. 



Keij to the species of genus Nocardia. 



I. Partially acid-fast* organisms with strongly refractive cells; non-proteolytic 

 and generally non-diastatic; constantly capable of utilizing paraffin. 



* Acid-fastness is not marked in cultures, is apparent in infected tissues, pro- 

 nounced in sputum or other e.xudates 



