Question

Give the difference between the cell walls of gram-positive and gram-negative bacteria.

Answer 1

Hint: The name comes from the bacteriologist Hans Christian Gram, who invented the technique to classify bacteria into two broad groups -gram-positive and gram-negative based on the staining process.

Complete answer:

Gram-positive bacteria	Gram-negative bacteria
The cell wall is single-layered and smooth	The cell wall is a double-layered structure and wavy in appearance
The thickness of the cell wall is about 20 to 80 nanometres	The thickness of the cell wall is 8 to 10 nanometres
The presence of the peptidoglycan layer which is multi-layered can be seen	The peptidoglycan layer is present but only a single layer is seen.
The presence of teichoic acids is seen	Teichoic acid is absent
Porins are absent on the membrane	Porins are present on the outer membrane
The lipid content of the wall is low	The lipid content of the wall is about 20 to 30%.
Lipopolysaccharide is absent	Lipopolysaccharide is present
Sulfur-containing amino acids are absent	Sulfur-containing amino acids are present in the cell wall.
The outer membrane is absent	The outer membrane is present
Rigid and less elastic	Less rigid and more elastic
Periplasmic space will be absent	Periplasmic space is present.
The bacteria falling under this category retain a crystal violet color even after they are washed with acetone or alcohol. And appear purple-colored when observed under a microscope	The type of bacteria falling under this category does not retain the stain even after they are washed with acetone or alcohol. They appear in pink colors when seen under the microscope
Examples- Streptococcus, Staphylococcus	Examples- Salmonella, Escherichia

Note: In phylum Chlamydiae, bacteria appear to lack peptidoglycan, although their cell walls have a gram-negative structure. Bacteria belonging to the phylum Tenericutes lack a cell wall altogether, which makes them susceptible to osmotic changes.