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THE ACTINOMYCETES, Vol. II 



tendency to become dark gray; frequently 

 black patches are produced in the mycelium, 

 the whole often becoming black. The sub- 

 strate growth is dark gray with a tendency to 

 become moist, slimy, and finally changing 

 to black. The species are melanin-negative, 

 although on synthetic agar a brown to black 

 soluble pigment may be produced. 



Morphologically the species give rise to 

 spiral-shaped sporophores. This series com- 

 prises a number of species, some of which 

 are listed: S. endus, S. hygroscopic us, S. 

 limosus, S. nigrificans, S. platensis, and S. 

 violaceoniger. 



X. Series Scabies 



Characteristic Properties 



a. Sporophores produce spirals. 



b. Aerial mycelium light gray to dark 

 gray. 



c. Melanin-positive. 



d. Some species are able to cause diseases 

 of plants, notably seal) of potatoes. 



The melanin-producing capacity of certain 

 actinomycetes, or their ability to form solu- 

 ble brown to black pigments when grown in 

 protein-containing media, was first recog- 

 nized as a diagnostic characteristic by lvossi- 

 Doria and Gasperini in 1891. Numerous 

 cultures found capable of producing such 

 pigments were isolated from different sub- 

 strates, and designated as Streptothrix chro- 

 mogena, Actinomyces chromogerms, or .1. 

 chromogenes. Gradually it came to be recog- 

 nized that all these isolates represented not 

 a single species but a large number of organ- 

 isms, differing greatly in their morphological, 

 physiological, and biochemical properties. 



This was definitely established in 1900 by 

 Beijerinck, who isolated two types of actino- 

 mycetes (" Streptothrix") represented abun- 

 dantly in nature. "One of these that I have 

 Learned to recognize in the form of numerous 

 varieties, 1 will designate as Sir. chromogena 

 Gasperini, since I believe that one such 



variety was available to the author of this 

 name. The other species I designate as Str. 

 alba." The first was characterized by the 

 formation of a brown pigment in meat ex- 

 tract-gelatin media. 



Neukirch (1902) demonstrated the pres- 

 ence in nature of two chromogenic types of 

 actinomycetes. Krainsky (1914) described 

 four chromogenic species, whereas Waksman 

 and Curtis (1916) demonstrated the occur- 

 rence in soil of various other chromogenic 

 types, "each with such well defined charac- 

 ters as to make it almost impossible to 

 classify them as one species." 



One of the most important series among 

 the chromogenic actinomycetes is S. scabies, 

 which at one time was designated as S. 

 chromogenus. In addition to the members of 

 the Chromogenus series as such, numerous 

 other species now included in other groups 

 also possess chromogenic properties, espe- 

 cially members of the Lavendulae and Re- 

 ticuli series. 



The soluble pigment produced by various 

 organisms when grown on protein-containing 

 media was found to belong to the melanin 

 type. It frequently involved the tyrosinase 

 reaction. The intensity of the pigment varies 

 with the organism and with the medium. 

 The formation of the melanin pigment is 

 usually determined by growing the organ- 

 isms on tyrosine-containing media. 



Baldacci et al. (1953) did not recognize a 

 "Chromogenus" series as such, although they 

 listed one under "Cas-Gri." Gause et al. 

 (1957) listed two series, one a "Chromogen us" 

 proper, and the other "Helvolus," in which 

 both pigment-producing and nonpigment- 

 producing types are included. 



The organisms belonging to S. scabies were 

 at first believed to be primarily associated 

 with scabbiness in white potatoes, sugar 

 beets, and mangels. Only the typical chro- 

 mogens were at first included in this series. 

 They formed a brown to dark brown to black 

 growth, a gray aerial mycelium, and a brown 



