Gram positive

Definition

Gram-positive bacteria are a group of bacteria that have a thick peptidoglycan layer in their cell walls, which retains the crystal violet stain used in the Gram staining procedure. They appear purple under a microscope after Gram staining.

5 Must Know Facts For Your Next Test

1. Gram-positive bacteria have a thick peptidoglycan layer in their cell walls.
2. Their cell walls contain teichoic acids, which contribute to their rigidity and charge.
3. Gram-positive bacteria retain the crystal violet stain during the Gram staining process, appearing purple under a microscope.
4. Examples of Gram-positive bacteria include Staphylococcus and Streptococcus species.
5. They are generally more susceptible to antibiotics that target peptidoglycan synthesis, such as penicillin.

Review Questions

• What color do Gram-positive bacteria appear after Gram staining?
• What is the primary structural component of the cell wall in Gram-positive bacteria?
• Name two examples of Gram-positive bacterial genera.

Related terms

Gram-negative bacteria: Bacteria that have a thin peptidoglycan layer and an outer membrane, appearing pink or red after Gram staining.

Peptidoglycan: A polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria.

Teichoic acids: Polymers found in the cell wall of Gram-positive bacteria that contribute to its rigidity and overall charge.