key term - Gram-negative cells

Definition

Gram-negative cells are a type of bacteria characterized by their cell wall structure, which includes a thin peptidoglycan layer and an outer membrane containing lipopolysaccharides. They do not retain the crystal violet stain used in Gram staining, appearing pink or red under a microscope.

5 Must Know Facts For Your Next Test

1. Gram-negative cells have an outer membrane that contains lipopolysaccharides (LPS), which can trigger strong immune responses in humans.
2. The thin peptidoglycan layer in Gram-negative bacteria is located between the inner cytoplasmic cell membrane and the outer membrane.
3. These cells are often more resistant to antibiotics than Gram-positive bacteria due to their unique outer membrane.
4. The periplasmic space in Gram-negative cells houses various enzymes that contribute to nutrient acquisition and antibiotic resistance.
5. During Gram staining, Gram-negative cells lose the initial crystal violet stain but take up the counterstain (safranin or fuchsine), resulting in a pink or red appearance.

Review Questions

Related terms

Gram-Positive Cells: Bacteria that retain the crystal violet stain during Gram staining, appearing purple due to their thick peptidoglycan layer.

Peptidoglycan:

A polymer that forms a mesh-like layer outside the plasma membrane of most bacteria, providing structural support.

Lipopolysaccharide (LPS): A large molecule consisting of lipid and polysaccharide found in the outer membrane of Gram-negative bacteria, known for its role in triggering immune responses.