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THE ACTINOMYCETES, Vol. II 



Flavus series have been isolated from soil, 

 dust, and other natural substrates by Krain- 

 sky, Waksman and Curtis, and others. They 

 have been designated by a variety of names, 

 such as S. alboflavus, S. aureus, S. citreus, 

 S. griseoflavus, and S. flaveolus. 



The Flavus series is characterized by 

 cream-colored to yellow or golden yellow 

 growth on most artificial media. The aerial 

 mycelium is usually white to gray to mouse- 

 gray. The sporophores are long, usually 

 spiral-shaped. The spores are spherical, us- 

 ually 0.7 n in diameter. No brown pigment 

 is produced on protein media. A yellowish- 

 green to golden pigment is often formed in 

 synthetic and organic media. The various 

 species in this group are strongly proteolytic 

 and diastatic. Sucrose is inverted. Nitrate 

 is reduced. Many of the strains are strongly 

 antagonistic and are able to form active 

 antibiotics, some of which have found ex- 

 tensive application as chemotherapeutic 

 agents. 



Krassilnikov (1949) recognized 13 distinct 

 species as belonging to the Flavus series. 

 Baldacci (1939), however, subdivided the 

 actinomycetes with the characteristics of 

 the Flavus series (various species producing 

 yellow or golden growth) into a number of 

 series: "aureus" "albidoflavus," "sulphur- 

 eus" ''antibiotic us," and u hygroscopieus.' n 

 Baldacci et al. (1954) included in the "Au- 

 reus" series such species as S. aureus, S. 

 aureofaciens, S. citreus, S. jimicarius, S. 

 flavus, S. flaveolus, S. fordii, S. griseoflavus, 

 S. hi/ijroscopicus, S. microflavus, and S. par- 

 vus. 



A culture of an organism isolated by 

 Takahashi (1953) in Japan was identified 

 by him as S. flaveolus Waksman. To validate 

 this identification, his description of this 

 culture is presented in Table 12 alongside 

 Waksman's description of the original type 

 culture. These data show that, in spite of 

 minor variations in color characterization, 

 quantitative differences in gelatin liquefac- 



tion and nitrate reduction, and even in 

 differences in antibiotic production, the 

 identification of the species appears to be 

 correct. 



The same is true of the characterization of 

 S. parvus. The original culture of this organ- 

 ism, which was used as the basis for its 

 description in Bergey's Manual, has died out 

 in the collection. Benedict, of the Northern 

 Regional Research Laboratory of the U. S. 

 Department of Agriculture, isolated from a 

 sample of soil collected in West Africa a 

 culture which he identified as S. parvus. A 

 comparison was made of the culture origi- 

 nally isolated and described by Krainsky 

 (1914), the culture isolated by Waksman 

 and Curtis (1916) and reported in Bergey's 

 Manual, and the new culture of Benedict 

 (Table 13). The results point definitely to 

 the identity of the three cultures, thus prov- 

 ing again that accurate identification of 

 some species can be made by comparing 

 freshly isolated cultures with written de- 

 scriptions of type isolates. 



Finally, a comparison was made (Waks- 

 man, 1957) of two published descriptions of 

 S. flavus and S. griseoflavus, together with 

 recent descriptions of two cultures that 

 have been raised to the status of new species, 

 namely, S. aureofaciens and S. rimosus, both 

 important producers of antibiotics. The re- 

 sults, presented in Table 14, show that S. 

 aureofaciens and S. rimosus are sufficiently 

 different from S. flavus and S. griseoflavus 

 to warrant the creation of new species. S. 

 aureofaciens is characterized by a deep gray 

 aerial mycelium, by a lack of or limited 

 spiral formation, by limited proteolytic ac- 

 tivity upon gelatin and milk, and by poor 

 growth on nutrient agar. It was concluded 

 that these properties differentiated this 

 culture sharply from the two older cultures. 

 S. rimosus is characterized by pool- growth 

 on synthetic agar and by the formation of 

 abundant spirals in its aerial mycelium. 

 These properties, together with certain 



