GENERAL BACTERIOLOGY 97 



2. Place four cultures of each organism in the water 

 bath and heat. 



3. Remove one of each at 40° C, one of each at 

 60° C, one of each at 80° C, and keep one of each for 

 10 minutes at 100°. 



4. Place one tube of each organism in the autoclave, 

 and heat to 120° C. for 5 minutes. 



5. Now place all twelve tubes in the thermostat, 

 including one of each organism as a control. 



6. After 24 hours, make plates of each tube in agar, 

 and place them in the thermostat. 



7. After 24 hours, count the colonies and compare 

 the results. 



SECTION 7 



STUDY OF CHROMOGENIC BACTERIA 



EXERCISE I. CULTURAL STUDIES 



References to chromogenic bacteria, and the pro- 

 duction and chemistry of pigments : 



Fischer's lectures, Fliigge, Die Mikroorganismen. 

 Lehmann and Neumann. 



Members of this group are widely disseminated in 

 the air, water, etc. A few representatives will be 

 studied. 



I. Inoculate agar slants from laboratory cultures of 

 Bacillus prodigiosus, B. pyocyaneus, B. violaceus, and 

 Sarcina lutea. Inoculate three slants each of B. 

 prodigiosus and B. violaceus, and one each of Sar. 

 lutea and B. pyocyaneus. 



