Lab midterm

If the chromophore is a positive ion like the methylene blue, the stain is considered

Basic
Most bacteria are stained when

a basic stain permeates the cell wall and adheres by weak ionic bonds to the negative charge of the bacterial cell
Simple stain

staining procedure that uses only one stain
Direct stain

simple stain that stains the bacteria
Negative stain

simple stain that stains the background but leaves the bacteria unstained
Staphylococcus epidermidis

round cluster
Bacillus megaterium

big rod
Which bacterium is a rod

Bacillus
Of what value is a simple stain

show size and morphology
What is the purpose of fixing the smear

help cells stick to slide so that they can be stained
In heat fixing, what would happen if too much heat were applied
- Too much heat would cause the cell's shape to distort.
- Denatures bacterial enzymes that cause the cells to break
Methylene blue can be prepared as a basic stain or an acidic stain. How would the pH affect the staining of bacteria

The pH will determine if the bacteria will have a particular charge
Can dyes other than methylene blue be used for direct staining

Yes. Crystal violet, basic fuchsin, and safranin are all dyes that can be used in direct staining because they are cationic which means they are positively charged
Bacteria can be seen without staining. Why then was Koch's recommendation for fixing and staining important in microbiology?

Allows bacteria to be saved and reexamined or shared

Author

micro

63893

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Lab midterm

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Lab midterm

Updated

2011-02-09T01:22:14Z

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