a) What is Gram staining? b) Describe step by step the procedure c) Explain the basis of Gram staining to differentiate bacteria (Use correct terminology)

Answer 1

a) Gram staining is a differential staining procedure used to help determine the type of cell walls their cells have, helping microbiologists differentiate the cells.

b) Procedure

1. Prepare a Heat-fixed Slide Smear
2. Crystal Violet is used to turn all of the cells purple.
3. Iodine, a mordant is used. This helps to stabilize the stains, trapping the stains inside the cells.
4. A decolorizing agent like ethanol is used. Cells who have thicker peptidoglycan walls will sustain the purple color, these are called Gram-Positive Cells. Cells who have thinner peptidoglycan walls will lose their purple color and become colorless. These cells are called Gram-Negative.
5. A counterstain, usually safranin, is used to turn the gram-negative cells a pink color so they can be visualized once again.

C) Gram staining is used to help microbiologists determine what type of cell walls their cells have. A cell that is gram-positive has thick peptidoglycan walls which helps trap the initial purple stain inside them, and can withstand the decolorizing agent. However, gram-negative cells have thinner peptidoglycan walls, which can be easily influenced by the decolorizing agent, and lose their initial purple color. When safranin is used, since the gram-negative cells have such thin walls, this color is easily taken up again.