Question
The negative stain shown in the photomicrograph below is most commonly used to determine ?
A. Cell size.
B. Cell arrangement.
C. Both of the above.
D. None of the above.
Show Answer
|
Correct Answer » C
Explanation
|
|
Stain shown in Photomicrograph above is most likely Nigrosin stain.
The negative stain is particularly useful for determining cell size and arrangement. It can also be used to stain cells that are too delicate to be heat-fixed.Nigrosin is an acidic stain. This means that the stain readily gives up a hydrogen ion and becomes negatively charged. Since the surface of most bacterial cells is negatively charged, the cell surface repels the stain. The glass of the slide will stain, but the bacterial cells will not. The bacteria will show up as clear spots against a dark background as represented in the photomicrograph above.
