Gram Staining

Question 1

What is gram staining?

Answer 1

A method used to divide bacteria into two groups so most effective treatment can be given. These are;
.Gram Positive
.Gram Negative

Question 2

What is the method of gram staining?

Answer 2

This method uses two stain which stain the cell wall

1. Add crystal violet (Purple)
2. Add Iodine (Purple)
3. Wash with grams destaining solution (G+- Purple G- - Colourless)
4. Add safranin (G+- Purple G- - Pink)

Question 3

Why does the gram positive bacteria appear purple at the end of the staining?

Answer 3

Gram positive bacteria have a thick layer of peptidoglycan. This retains the crystal violet, so they appear violet.

Question 4

Why does the gram negative bacteria appear pink?

Answer 4

Gram negative bacteria have a wall made of a thin layer of peptidoglycan so they lose the purple stain when the destaining solution is added. Gram negative bacteria then stain pink with the safranin.

Question 5

Why can antibiotics enter a gram-positive bacteria?

Answer 5

They have a wall made of a thick later of peptidoglycan and no outer lipopolysaccharide membrane SO they are more susceptible to some antibiotics such as penicillin that an damage the peptidoglycan layer and enter the cell.

Question 6

Why can’t antibiotics enter a gram-negative bacteria?

Answer 6

They have a wall made of a thin layer of peptidoglycan and an outer lipopolysaccharide membrane SO they are not susceptible to SOME antibiotics such as penicillin, BECAUSE the peptidoglycan layer is protected by the lipopolysaccharide outer membrane so it is impermeable so they antibiotic can’t enter the cell.

Question 7

Why is it important to know if a bacteria is gram positive or gram negative?

Answer 7

Different antibiotics are used to treat each type of bacteria

Question 8

Which bacteria is more resistant and harder to treat?

Answer 8

Gram negative.