120 GENERAL MICROBIOLOGY 



one tube sterile 2% saccharose broth; one tube sterile 

 2% glycerin broth; one tube sterile nutrient broth; three 

 tubes sterile wort; three tubes sterile gelatin; four tubes 

 sterile dextrose agar; gasometer; 10% NaOH. 



Cultures. Saccharomyces cerevisice;* Saccharomyces 

 apiculatus; Torula rosea. 



Method. 1. Fill one fermentation tube with each broth. 

 Sterilize by heating one-half hour in the steam on three 

 consecutive days. 



2. Make cultures of each yeast in 

 (a) Beer wort. 



(6) Gelatin (stab culture). 



(c) Dextrose agar slant. 



(d) Dextrose agar plate (giant colony). f 



(e) Linder's concave slide culture (p. 83). 



3. Make cultures of Saccharomyces cerevisice only, in 

 fermentation tubes of 



(a) Plain broth control (without carbohydrate). 



(b) 2% dextrose broth. 



(c) 2% lactose broth. 



(d) 2% saccharose broth. 



(e) 2% glycerin broth. 



4. Prepare an adhesion culture from freshly inoculated 

 wort culture of the yeast (see p. 78). 



5. Examine microscopically immediately after prepara- 

 tion and draw single cells and cells in various stages of 

 budding (germination); show interior structure of cells. 



6. Examine all cultures after twenty-four hours, and make 

 drawings of (a), (b), (c), (d), and (e) under 2 ; place as 

 indicated on chart, and label correctly. 



7. Describe all gelatin and agar cultures according to 

 the descriptive chart of the American Society of Bacteriol- 



* Saccharomyces cerevisioe has been previously isolated from a fresh 

 cake of Fleischmann's compressed yeast. (See Exercise 40.) 



t Only one plate is necessary. All yeasts may be grown on one 

 plate. Use dextrose agar. 



