56 STUDYING MOLDS, YEASTS, AND ACTINOMYCETES 



This medium has been used by Thom for descriptions of species of 

 Penicilhum and Aspergillus, and by Waksman for descriptions of 

 soil actinomycetes. In both cases color of the growth is of great 

 importance in identification. Many fungi cannot, however, readily 

 use sucrose, others cannot utilize nitrates. This medium cannot 

 therefore be used for all fungi. An alternative medium is that of 

 Barnes: 



Tripotassium phosphate 10 grams 



Ammonium nitrate 10 grams 



Potassium nitrate 10 grams 



Glucose 10 grams 



Water 1 liter 



All these synthetic media may, of course, be solidified by the addi- 

 tion of agar unless they are so acid as to hydrolyze agar. 



Many if not most fungi require minute amounts of other elements, 

 e.g., zinc, but unless purely synthetic media prepared from specially 

 purified chemicals in special glassware are used, sufficient traces of 

 these elements will usually be provided by the ingredients used, the 

 water, or the glassware. Also some fungi require small amounts of 

 growth-promoting substances and in purely synthetic media these 

 may need to be provided for. 



Dye Media. Various workers have experimented with the addi- 

 tion of dyes to culture media used for the identification of fungi, 

 either to stain the growing mycelium differentially or to serve as pH 

 indicators. Williams ** grew a variety of fungi, mostly pathogenic 

 species, on a 4 per cent peptone, 1 per cent glucose agar to which was 

 added nigrosin, litmus, eosin Y, eosin B, fluorescein, methylene blue 

 and eosin, Wright's stain, neutral red, and Janus green. Von Mal- 

 linckrodt-Haupt ^* grew various dermatophytes on media containing 

 thymol blue, bromophenol blue, bromocresol purple, bromothymol 

 blue, phenol red, and cresol red. Although the various cultures 

 showed differing degrees of dye absorption by the growing fungi, or 

 color changes in the media, no useful differential media have de- 

 veloped from the studies. Negroni and Loizaga ^- grew Candida 

 albicans in a beer wort to which were added basic fuchsin, methylene 

 blue, gentian violet, malachite green, and methyl green in minute 

 quantities (1:50,000-1:10,000). These basic dyes, especially methyl 

 green, induced the production of rough variants. 



Quantity Production of Mold Mycelium. In many types of re- 

 search, as for obtaining antigens, enzymes, antibiotics, or other in- 

 tracellular products or for large amounts of growth for chemical 

 analyses or animal feeding experiments, it is desirable to obtain a 



