Which of the microscope objectives is most satisfactory for studying bacteria? Why?



1.  How does true motility differ from Brownian movement?


2.  What morphological structure is responsible for bacterial motility?


3.  Why is a wet preparation discarded in disinfectant solution or biohazard container?

4.  What is the value of a hanging-drop preparation?


5.  What is the value of a wet-mount preparation?



1.  Define acidic and basic dyes. What is the purpose of each?


2.  What is the purpose of fixing a slide that is to be stained?


3.  Why are the specimens to be stained suspended in sterile saline or


distilled water?


4.  Which of the microscope objectives is most satisfactory for studying bacteria? Why?

5.  How does a stained preparation compare with a hanging drop for studying the morphology and motility of bacteria?

6.  List and define the basic shapes of bacteria. What are the dimensions of an average bacillus in micrometers? In centimeters?

7.  List at least three types of bacteria whose names reflect their shapes and arrangements, and state the meaning of each name.

8.  For what reason do we need to stain bacteria?




1.  What is the function of the iodine solution in the Gram stain? If it were omitted, how would staining results be affected?

2.  What is the purpose of the alcohol solution in the Gram stain?


3.  What counterstain is used? Why is it necessary? Could colors other than red be used?

4.  On the basis of Gram-stain reaction, can you distinguish species of:

Staphylococcus and StreptococcusStaphylococcus and NeisseriaEscherichia and ProteusEscherichia and Bacillus?

5.  What is the size of staphylococc i in micrometers? In centimeters?

6.  What is the advantage of the Gram stain over a simple stain such as methylene blue?

7.  In what kind of clinical situation would a direct smear report from the laboratory be of urgent importance?

8.  What is the current theory about the mechanism of the Gram-stain reaction?

9.  Describe at least two conditions in which an organism might stain gram variable.

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