PART II 

 PHYSIOLOGY OF MICROORGANISMS 



EXERCISE 1. TO DEMONSTRATE THE SMALL AMOUNT 

 OF FOOD NEEDED BY BACTERIA 



Apparatus. Distilled water; eleven sterile Petri dishes; 

 sterile 1 c.c. pipette; sterile 10 c.c. pipettes; eight sterile 

 200 c.c. flasks; eleven tubes of sterile agar (ordinary). 



Cultures. B. coli. 



Method. 1. Place 150 c.c. of distilled water in each of 

 two sterile flasks. 



2. Sterilize one flask (flask B) in the autoclav for ten 

 minutes at 15 Ibs. pressure (120 C.). 



3. Plate 1 c.c. from the remaining flask (flask A), imme- 

 diately on agar. 



4. As soon as flask B is cold, plate 1 c.c. 



5. Then inoculate the water in flask B with B. coli, using 

 the straight needle and transferring a very small amount, and 

 plate 1 c.c. 



6. Place flasks A and B and the plates made from the 

 flasks at room temperature. 



7. Prepare four 90 c.c. and two 99 c.c. dilution flasks and 

 sterilize. 



8. At the end of five days, plate from flasks A and B, 

 using 1 c.c. direct and dilutions 1 : 10, 1 : 100 and 1 : 1000. 

 Incubate the plates at room temperature. 



9. Count each set of plates at the end of five days' 

 incubation. 



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