Question

For each of the following items, state: "Gram " if it is seen in just Gram positive bacteria, "Gram -" if it is seen just in Gram negative bacteria, or "both" if it is seen in both Gram positive and Gram negative bacteria.

1) A cell wall that is made of peptidoglycan
2) A cytoplasmic membrane composed of phospholipids and protein
3) An outer membrane that includes lipopolysaccharide (LPS)
4) A thick cell wall that causes the bacteria to be purple in the Gram stain
5) Teichoic acids and lipoteichoic acids embedded in the cell wall
6) A thin cell wall that causes the bacteria to be red in the Gram stain

Answer 1

1) A cell wall that is made of peptidoglycan BOTH

2) A cytoplasmic membrane composed of phospholipids and protein BOTH

3) An outer membrane that includes lipopolysaccharide (LPS) GRAM-

4) A thick cell wall that causes the bacteria to be purple in the Gram stain GRAM+

5) Teichoic acids and lipoteichoic acids embedded in the cell wall GRAM+

6) A thin cell wall that causes the bacteria to be red in the Gram stain GRAM-

Both of them have peptidoglycan layer in their cell wall, but the one in Gram + is thick (multilayered), while the one in Gram- is thin. This is the reason why the crystal violet dye retain in the walls of Gram + causing them to be purple (Gram – stay red). Gram- are more resistant against antibodies because of their impenetrable cell wall.