Exercise 2
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45 Terms
What is the purpose of staining and what do you use to view the stained slide?
makes it easier to view bacteria using a bright field microscope
What do bacteria lack that staining helps with?
bacteria lack contrast, staining provides that contrast
What are MOST staining procedures useful for?
identifying morphology, size, and arrangement
what are the 3 types of staining?
simple, differential, and structural
What is simple staining and what is the result of the stain?
one stain is used to dye ALL cells present, all cells will be the SAME color
What is differential staining?
used to differentiate bacteria based on certain characteristics
What is the name of the type of stain that is classification because of its very own unique procedure?
Negative stain
What are the two main types of dyes used?
cationic and anionic
What are cationic dyes?
they are BASIC dyes, positively charged chromophores
In cationic dyes, what ions exhibits the color of the dye?
positive ions
what are cationic dyes attracted to? what is the result?
net negative charge of bacterial cells, they actually stain the cells themselves
What are two examples of cationic dyes?
methylene blue and crystal violet
What are anionic dyes?
they are ACIDIC dyes, negatively charged chromophores
In anionic dyes, what ions exhibits the color of the dye?
Negative ions
what are anionic dyes repelled to? what is the result?
repelled by negative charge, cell is NOT stain but rather the background
What are three examples of anionic dyes?
Acid fuchsin, congo red, nigrosin
What type of dye does a negative stain use?
Anionic dye
Since you are using an anionic dye for a negative stain, what will you see?
Transparent cells against a colored background
What two things are best seen with a negative stain? What is it useful for?
good for examining morphology and size of bacterial cells. useful for organisms that don’t stain easily
do you heat fix negative stains?
no
what is one example of a dye that is used for negative stain?
nigrosin