N().Mi:\("i,A'i"ri{i; and (;i:\i:i{ ai, s^•s■|'l:^ls oi' ci-assii'icatiox 



Sin plosponiiKiinin , and Tin rmojidh/spord, ap- 

 pear to ros(Mnl)lo those ol' t'uii}^;!. 



■J. Tlie natun> ot" \\w lii'owili ol' many acti- 

 iioniycetes (Ui \\\c surlace ol li(|iii(l and solid 

 niinlia and tlieir growth in a suspended or 

 submerged concUtion are similar to tliose of 

 fungi. Stationary licjuid cultures of aetino- 

 myeotes do not usually show turbidity . In 

 tiiis, they are similar to the fungi. 



.">. Pleomorphism of certain actinomycetes 

 shows similarity to that of fungi ((Irigorakis). 



4. Roach and Sih'ey l)elie\-ed that the 

 e\-idence for the origin of the secondary 

 mycelium lends credence to the theories of 

 those investigators who belie\'e actinomy- 

 cetes are true fungi. 



An early student of the morphology of 

 actinomycetes, Domec, concluded that these 

 organisms must definitely be removed from 

 the bacteria and placed with the fungi. Vuil- 

 lemin (19."31), who considered the causative 

 agent of "farcin du boeuf" as a species of 

 Xocardia {N . farcinica), also believed that 

 the group as a whole belongs to the fungi, in 

 the family Microsiphonales, in the order 

 Arthrospora. The mycobacteria were also 

 placed in this family. Among the earlier 

 investigators who classified the actinomy- 

 cetes with the fungi were Harz, Gasperini, 

 Sauvageau and Radais. More recently, Prid- 

 ham ct al. (1958), on the basis of their mor- 

 jihological studies, were also inclined to 

 classify the actinomycetes, especially the 

 genus Strcptomyces, with the fungi. 



Transition group. Because of these appar- 

 ently^ conflicting facts, the suggestion has 

 been made that actinomycetes should be 

 placed in a taxonomical transition group 

 between the Schizomj^cetes and the Hypho- 

 mycetes. Many highly heterogeneous prop- 

 erties of some of the actinomycetes, espe- 

 cially those of a morphological nature, have 

 further strengthened the idea of placing them 

 between the true bacteria and the true fungi. 



Among the investigators who held to the 

 middle position, one should mention Rossi- 



FiGLRE 24. Broom-shapod sporophores of a 

 .streptomyces. 



Doria, Kruse, Claypole, Lieske (in his later 

 work, 1928), Waksman (especially in his 

 earlier work), and Krassilnikov. Krassil- 

 nikov looked upon the actinomycetes as an 

 independent group of microorganisms with 

 its own typical morphological, cultural and 

 physiological properties. 



Classification Systems of Actinomycetes 



Numerous systems have been proposed for 

 classifying actinomycetes. These were based 

 upon the causation of disease and the ecology 

 of the organisms, their morphology (struc- 

 ture of sporophores, shape of spores), cul- 

 tural activities (growth on ^'arious media), 

 physiological (oxygen tension, temperature 

 optima) and biochemical (enzymatic mecha- 

 nisms, sugar utilization, acid production) 

 properties, serum diagnosis, and formation 

 of soluble and insoluble pigments. 



Buchanan made a comprehensive re\iew 

 of the various sj^stems of bacterial classifica- 

 tion, in which the natural position of the 

 bacteria (beginning with Mueller's classifica- 

 tion of Vermes in 177o) was outlined, as well 

 as the position of the actinomj'cetes among 

 the bacteria (utilizing Cohn's system of 



