Microbiology Lab
Exercise 2 Microscopy
and Staining Exam
Questions and Complete
Solutions Graded A+
Denning [Date] [Course title]
, staining - Answer: can be used to make it easier to view bacteria using a bright field microscope and
provides contrast
what is staining useful for identifying? - Answer: morphology, size and arrangement
what are the 4 different types of staining? - Answer: simple, differential, structural and negative
what type of staining is this exercise? - Answer: simple
differential staining - Answer: differentiate bacteria or microbes based on certain characteristics
cationic dyes - Answer: basic dyes, positively charged chromophore
what are cationic dyes attracted to? - Answer: net negative charge of bacterial cells and stain the cells
what are two examples of cationic dyes? - Answer: methylene blue and crystal violet
anionic dyes - Answer: acidic dyes, negatively charged chromophore
what are anionic dyes repelled by? - Answer: the negative charge of the bacterial cell, the background of
the cell is dyed
what is an example of an anionic dye? - Answer: nigrosin
negative stain - Answer: - uses an anionic dye, so the stain does not penetrate the cell
- the cells are repelled by the negatively charged dye and have transparent cells against a colored
background
what is a negative stain good for? - Answer: examining morphology and size of bacterial cells because
heat is not used, so distortion of the bacterial cells is minimized
Exercise 2 Microscopy
and Staining Exam
Questions and Complete
Solutions Graded A+
Denning [Date] [Course title]
, staining - Answer: can be used to make it easier to view bacteria using a bright field microscope and
provides contrast
what is staining useful for identifying? - Answer: morphology, size and arrangement
what are the 4 different types of staining? - Answer: simple, differential, structural and negative
what type of staining is this exercise? - Answer: simple
differential staining - Answer: differentiate bacteria or microbes based on certain characteristics
cationic dyes - Answer: basic dyes, positively charged chromophore
what are cationic dyes attracted to? - Answer: net negative charge of bacterial cells and stain the cells
what are two examples of cationic dyes? - Answer: methylene blue and crystal violet
anionic dyes - Answer: acidic dyes, negatively charged chromophore
what are anionic dyes repelled by? - Answer: the negative charge of the bacterial cell, the background of
the cell is dyed
what is an example of an anionic dye? - Answer: nigrosin
negative stain - Answer: - uses an anionic dye, so the stain does not penetrate the cell
- the cells are repelled by the negatively charged dye and have transparent cells against a colored
background
what is a negative stain good for? - Answer: examining morphology and size of bacterial cells because
heat is not used, so distortion of the bacterial cells is minimized
