4U2 BACTERIA 



IV. Incubate the six dishes for twenty-four hours. 



V. Make repeated daily observations. 



A. Which material used seems to be of least use in checking the 

 growth of bacteria? 



1. Compare the growth of colonies in this dish with your control. 



B. Give the effects of each of the other solutions on the growth of 

 bacteria. 



C. Which antiseptics might be unwise to use on delicate lining mem- 

 branes such as those in the throat, nose, and eye? 



VI. The experiment may be repeated to test the results of various mouth 

 washes. 



VII. Antiseptics should be used with great discretion. Some of them kill 

 bacteria rather than check their growth. They are called germicides. Those 

 that check the growth of bacteria are the true antiseptics. Germicides may kill 

 the tissues as well as the bacteria. This, in many cases, will check healing. 



Questions and Suggestions 



1. Describe the structure of bacteria. 



2. Classify bacteria according to their shape. Give some in- 

 dividual variations of each type. 



3. What are aerobic and anaerobic bacteria ? 



4. Discuss three different types of nutrition found among bacteria. 

 Give an example of each type. 



5. Discuss reproduction and spore-formation. 



6. Name five methods used in the identification of bacteria. 



7. What is the importance of agar ? 



8. Discuss the sterilization of agar and of Petri dishes. Discuss the 

 methods of inoculation, and conditions for the cultivation of bacteria 



9. Discuss favorable conditions for the growth of bacteria. Which 

 of these conditions are found in the human body? 



10. Under what conditions will food spoil ? 



11. Name some conditions unfavorable for the growth of bacteria. 



12. Give in the form of an outline the method of preserving certain 

 foods from the activities of bacteria, and the resulting conditions that 

 are unfavorable for their growth. 



13. Discuss the relative number of bacteria in different types of air. 



14. Discuss the bacterial content of different types of milk. 



15. What is the relation of different antiseptics to the growth of 

 bacteria ? 



