What is the diffrence between gram-positive and gram-
negative bacteria?
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Answer Posted / david
Gram positive bacteria are those retain crystal violet dye
in gram staining protocol.They retain dark blue dye after
an alcovol wash.while Gram negative bacteria are those do
not retain crystal violet dye in gram staining
protocol.Gram stain test a counterstain (saffranin)is added
after crystal violet coloring all Gram Negative bacteria
apper red or pink.
The major difference between gram positive and gram
negative bacteria lie in the chemical compostion of their
cell wall.
1. Gram +ve bacteria has got higher amount of peptidoglycan
compared to gram negatives. this cross linked peptidoglycan
is responsible for retaining the crystal violet during gram
staining.
2. Gram -ves has lower peptidiglycan but has got a lipid
layer in the cell wall. tHis lipid is gets extrcted away
during alcohol destaining in gram's stainig proceduremaking
the cell wall more permeable and thus crystal violet is not
reained and take the counterstain saffranin
3. gram+ves has teichoic acid in cell wall but gram -ves do
no not.
4.gram -ve cerll wall has got lpopolysaccharides which is
responsible for its endotoxic and antigenic property
gram +ve bacteria's are sphericl/cocci in shape, which has
outer phospolipid layer and lower is peptidogycan layer
which consist of nicotinamide diphosphate and nicotinamide
sulphate chain which are linked by weak glycopeptide bond
due to which when gram staining is performed it retain
methylene blue dye while not that counter(saffranin)stain
which is wash due to alcohol and appear violet/purple in
colour.
while in case of gram -ve are rod shape they appear pink in
colour,since retain counter stain and while addition of
alcohol they shrink out ,capture counter stain,also
composed of outer peptidiglycan and inner phospholipid
layer.
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