Gram Staining

Question 1

Gram Staining Procedure?

Answer 1

procedure consists of the application of crystal violet stain, followed by a mordant (Gram’s iodine), decolourisation with alcohol or acetone, and counterstain with safranin.

Question 2

What are the results if Gram Stain was +ve

Answer 2

would remain purple in colour
.
- (due) to the bacteria held onto the dye during the decolorizing step, resulting in a positive result

Question 3

What are the results if Gram Stain was -ve

Answer 3

A gram-negative bacteria appears pink or red under a mircoscope.

• (due) to having a thinner peptidoglycan cell wall than Gram-positive bacteria. This means they don’t retain the blue dye used in Gram staining and instead take up the red/pink counterstain (safranin) applied afterwards

Question 4

large?!

Gram +ve bacteria has a () peptidoglycan layer therefore?

Answer 4

has a thick peptidoglycan layer therefore struggle to lose the purple stain appiled previously.

Question 5

pettite

Gram -ve bacteria has a () peptidoglycan layer so therefore.

Answer 5

Has a thin peptidoglycan layer so therefore loses the purple stained previously appiled so therefore only safranin (the recent stain) is reflected under the mircoscpe after the whole gram-staining.