What is the diffrence between gram-positive and gram-
negative bacteria?
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Answer Posted / sayantani das
Bacteria are generally classified into two groups on the
basis of Gram staining based on the amount of peptidoglycan
present in the cell wall.Though it is found that Gram
positive and gram negative bacteria have certain other
variable characteristics other than merely the result of
Gram staining:
Gram positive-
1.They retain the crystal violet stain after gram staining.
2.They have peptidoglycan layer thickness about 20-80nm and
about 40-60 layers thick.
3.Peptidoglycan is much more mesh like and has interpeptide
cross linkages.
4.cell wall has techoic acids which confer negative charges
to the cell wall.
5.Have only one periplasmic space.
Gram negative-
1.They retain the colour of safranine,the counter stain of
gram stain, and not the colour of the primary stain crystal
violet.
2.The cell wall has an additional layer outside the
peptidoglycan layer known as the outer membrane.
3.The outer membrane contains lipid-A,core polysaccharide
and the O-side chain.
4.Lipid A portion of core polysaccharide is known as
endotoxin and help in virulence.
5.O side chain is also known as o specific antigen as it
elicits an immune response.
6.Peptidoglycan has a thickness of 2-7 nm .
7.It has two periplasmic spaces on either side of
petidoglycan layer.
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