- In Gram positive bacteria cell wall is made up of 2 layers.
- A thicker outer layer made of peptidoglycan and the cell membrane
- A lipid rich outer wall
- A middle layer consists of thin layer of peptidoglycan and cell membrane.
|Gram Positive Bacteria|
|Gram Negative Bacteria|
- Gram positive cells appear violet or purple (Colour of crystal violet)
- Gram negative cells appear pink to red (colour of safranin).
- Crystal violet solution: 1g crystal violet dissolved in 100 ml ethanol
- Safranin solution: 1g safranin dissolved in 100 ml H2O.
- Iodine solution: Dissolve 2g potassium iodide (KI) in 100 ml water. To the solution add iodine crystals till a deep yellow colour develops.