50 



THE ACTIXOMYCETES, Vol. I 



Sanfelice emphasized, in 1904, the lack of 

 constancy of actinomycete characters when 

 the organisms are grown on ordinary culture 

 media. He abandoned the species concept 

 altogether and suggested establishment of 

 three groups of actinomycetes, each center- 

 ing around a type species. The groups thus 

 recognized were -4. flavus, A. albus, and .4. 

 violaceus. Unfortunately, the complex or- 

 ganic media used by Sanfelice did not permit 

 the proper comparisons even of the salient 

 features of the specific organisms. He recog- 

 nized, however, the value of the pigmenta- 

 tion in classifying actinomycetes, a fact 

 supported by numerous subsecjuent investi- 

 gators (Conn and Conn, 1941). 



Another 10 years elapsed before the work 

 of Krainsky (1914), on the one hand, and of 

 Waksman and Curtis (1916), on the other, 

 which recognized the unsatisfactory condi- 

 tion of using the common complex organic 



Figure 21. Cirowth of a stroptomvccs ])n)(luc 

 ing straight sporophorcs. 



bacteriological media for characterizing 

 actinomycetes. Krainsky's important con- 

 tribution to the study of actinomycetes was 

 the introduction of simple synthetic media. 

 He classified the 18 species that he described 

 on the basis of three types of chromogenesis : 

 (a) organisms that secrete soluble pigments 

 into the medium; (b) organisms that produce 

 insoluble pigments, only the colony being 

 colored; (c) those organisms that form a 

 pigmented aerial mycelium. When grown on 

 proper media, each species showed charac- 

 teristic properties, based upon the above 

 three types of pigmentation. These prop- 

 erties are now universally recognized, in 

 addition to morphological and certain bio- 

 chemical characteristics, as among the most 

 essential in establishing species of actino- 

 mycetes. Krainsky further divided his cul- 

 tures into two groups, on the basis of the 

 size of the colony : (a) a macrogroup produc- 

 ing large colonies with oval or spherical 

 conidia; (b) a microgroup producing small 

 colonies and spherical conidia only. Un- 

 fortunately, however, he did not study the 

 morphology of the aerial mycelium. 



Soon afterward, Waksman and Curtis 

 published descriptions of 18 additional 

 species. Their classification was also based 

 upon pigmentation of the cultures in syn- 

 thetic and organic media and upon certain 

 cultural and morphological properties, such 

 as li(iuefaction of gelatin. They disregarded 

 the size of the colonies and emphasized spiral 

 formation in the aerial mycelium as charac- 

 teristic criteria in species differentiation. 

 Waksman (1919) further recognized the 

 importance of the group concept in charac- 

 terizing and classifying actinonwcetes. With 

 the rapid increase in the number of new 

 species described, this concept recently has 

 been gaining ever greater recognition. 



This brief re^dew of the early attempts at 

 nomenclature and classification of actino- 

 mycetes brought out the fact that two 

 generic names, Streptothrix and Actinomyces, 



