Question

1) You are performing an endospore stain of a 72 hour Clostridium sporogenes culture. You forget to turn on the heat on your water beaker. What will you see under the microscope:

a) Spores will be green

b)Everything will be green

c) vegetative cells will be pink

e) everything will be pink

2) You are performing an acid-fast stain of Mycobacterium smegmatis and forget to use the acid alcohol. WHat color will the cells appear under the microscope?

a)green or blue

b) purple

c) pink

d)colorless

3) You are performing a capsule stain and only see a dark background with no white spaces. Why?

a)the cell does not have a capsule

b) the bacteria was not added

c) crystal violet was not added

d) two of the choices are possible

4) What is NOT an advantage of having a capsule?

a) to avoid drying out

b) to avoid being eaten via phagocytosis

c) to use as food

d) to survive unfavorable conditions

5) Which of the following pairs is mismatched:

a) Carbolfuchsin: primary stain

b) alcohol: mordant

c) brilliant green: secondary stain

d) Carbolfuchsin: basic dye

Answer 1

Q1

e) everything will be pink

Explanation: Heat fixes the bacteria to the glass slide. It will also helps to fix primary stain malachite green on endospore. If heating will not be proper then endospore and the primary stain will be removed while washing step and everything will appear as pink due to addition of counter stain.

Explanation for wrong answers

A and B. Endospore and the primary stain will be removed during washing step therefore green colour will not be present.

C. Vegetative cells will be converted to endospore at 72 hr. Therefore, no vegetative cells are present in the culture.

Explanation for wrong answers

Q2

Pink.

Explanation: Carbolfuchsin is the primary stain used in the acid fast staining. Acid alcohol removes this stain from non acid fast bacteria. And non acid fast bacteria will be stained with methylene blue, counter stain, and appear as blue. If acid alcohol will not be used then primary stain will not be removed from non acid fast bacteria and everything will appear as pink.

Explanation of wrong answers

a and b. Primary stain is giving pink colour therefore in the absence of acid alcohol blue, green or purple will not formed.

d. Acid fast bacteria will take primary stain and therefore colourless bacteria will not be there.

Q3

Cell does not have capsule

Explanation. Only cells having capsule will show white colored ring on dark background. Capsule is the gelatigenous material secreted by the cells and it adhere to the cell wall to form a layer. Capsule staining involves the the use of basic and acidic dyes. Basic dyes are used for staining background and acidic dyes are used for staining capsule to form white ring.

Explanation for wrong answers

b. If bacteria will not add then background will not be dark.

c. Crystal violet causes background to dark. If background is dark then crystal violet must be present.

Q4

To use as food

Explanation: Capsule is not used as the food. It plays the important function which is given in the other options.

Explanation for wrong answers

All the remaining options are the true functions of the capsule.

Q5

b.
Explanation. Heat is generally act as mordant.