Chapter II —4^— Important Types 



Pigment production (golden yellow) is well developed in most 

 strains of this organism grown on meat extract-asparagine-glucose agar, 

 or on potato-dextrose agar, and on potato plugs. The substrate my- 

 celium of young colonies is hyaline at first, commonly becoming yellow 

 in 2 to 3 days. The aerial mycelium is white. The first-formed spores 

 are white, but the entire heavily sporing surface of a slanted agar cul- 

 ture gradually changes in 5 to 7 days at 28 °C. through brownish gray 

 to a dark, drab gray. At the same time most of the substrate mycelial 

 color disappears. The reverse color of slants at its best is golden tan, 

 later tawny. 



Aureomycin is a weakly basic compound which contains both nitro- 

 gen and nonionic chlorine. Aureomycin when treated with alcoholic 

 ferric chloride gives a greenish-brown color by reflected light and red- 

 dish color by transmitted light. The crvstalline free base has the fol- 

 lowing properties: m.p., 168-169°C; solubility in water, 0.5-0.6 mg/ml 

 at 25 °C; soluble in the cellosolves, dioxane, and carbitol; slightly soluble 

 in methanol, ethanol, butanol, acetone, ethyl acetate, and benzene; in- 

 soluble in ether and petroleum ether; very soluble in aqueous solution 

 above pH 8.5, 



Stre'ptoviyces scabies (Thaxter) Waksman and Henrici 



Morphology: wavy or slightly curved mycelium, with long branched 

 aerial hvphae, showing a few spirals. Conidia more or less cylindrical; 

 0.8 to LO by 1.2 to 1.5[x. 



Gelatin stab: Cream-colored surface growth, becoming brown. Slow lique- 

 faction. 



Synthetic agar: Abundant, cream-colored, wrinkled, raised. Aerial mycelium 

 white, scarce. 



Starch agar: Thin, transparent, spreading. 



Dextrose agar: Restricted, folded, cream-colored, entire. 



Plain agar: Circular, entire colonies, smooth, becoming raised, lichenoid, 

 wrinkled, white to straw-colored, opalescent to opaque. 



Dextrose broth: Ring in form of small colonies, settling to the bottom. 



Litmus milk: Brown ring with greenish tinge; coagulated; peptonized with 

 alkaline reaction. 



Potato: Gray, opalescent, becoming black, wrinkled. 



Nitrites produced from nitrates. 



Brown soluble pigment formed. 



Peptonization of milk and gelatin. 



Starch is hydrolyzed. 



Aerobic. 



Optimum temperature: 37°C. 



Habitat: Soil; cause of potato scab. 



This is a large heterogeneous group of organisms, occurring in nature 

 in the form of many strains. A number of specific organisms, said to be 



