Answer / nimi narayanan

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

Answer / amol vibhute

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.

Answer / 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.

Answer / sushworld

i want to focus just on staining.
gram +ve are those which are stained by crstal violet
stain. the gram -ve are also stained by crystal violet but
this stain is removed by washing it with 95% alcohol.this
is because it has lipids in it's cell wall which causes
pores in it's wall & lets the stain to escape.
It is hence stained with a counter stain saffranin which
gives it a pink colour.

Answer / 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.

Answer / olaoluwa

gram +ve bacteria's wall contain 3 or 4 amino acids
including alanine glutamic acid and lysine(diaminopimelic
acid ) while the gram -ve bacteria's wall contains most
amino acids plus diaminopimelic acid

Answer / martin karanja muthama,kenya(u

1.g+ve has a thicker layer of peptidoglycan as compared to
g-ve 2.g+ve got teichoic acid unlike in g-ve 3.g-ve have a
perisplamic membrane which is absent in g+ve. 4.g+ve lack
lipoproteins which are present in g-ve.5.g-ve has a LPS
(LIPOPOLYSACCHARIDE LAYER)which is absent in g+ve

Answer / r.sathish kumar

Gram-positive bacteria are those that are stained dark blue
or violet by Gram staining. This is in contrast to
Gram-negative bacteria, which cannot retain the crystal
violet stain, instead taking up the counterstain (safranin
or fuchsine) and appearing red or pink. Gram-positive
organisms are able to retain the crystal violet stain
because of the high amount of peptidoglycan in the cell
wall. Gram-positive cell walls typically lack the outer
membrane found in Gram-negative bacteria.

When treated as a clade, the term "posibacteria" is
sometimes used.
Characteristics
Gram-negative bacteria
Gram-negative bacteria (or negibacteria) are bacteria that
do not retain crystal violet dye in the Gram staining
protocol.[1] In a Gram stain test, a counterstain (commonly
safranin) is added after the crystal violet, coloring all
Gram-negative bacteria with a red or pink color. The test
itself is useful in classifying two distinct types of
bacteria based on the structural differences of their
bacterial cell walls. Gram-positive bacteria will retain the
crystal violet dye when washed in a decolorizing solution.

The pathogenic capability of Gram-negative bacteria is often
associated with certain components of Gram-negative cell
walls, in particular, the lipopolysaccharide layer (also
known as LPS or endotoxin layer).[1] In humans, LPS triggers
an innate immune response characterized by cytokine
production and immune system activation. Inflammation is a
common result of cytokine (from the Greek cyto, cell and
kinesis, movement) production, which can also produce host
toxicity.

When treated as a clade, the term "negibacteria" is
sometimes used.[2]
Gram-positive and -negative cell wall structure
Structure of Gram-positive cell wall

The following characteristics are generally present in a
Gram-positive bacterium:[2]

cytoplasmic lipid membrane
thick peptidoglycan layer
teichoic acids and lipoids are present, forming
lipoteichoic acids, which serve to act as chelating agents,
and also for certain types of adherence.
capsule polysaccharides (only in some species)
flagellum (only in some species)
if present, it contains two rings for support as
opposed to four in Gram-negative bacteria because
Gram-positive bacteria have only one membrane layer.
The individual peptidoglycan molecules are cross-linked
by pentaglycine chains by a DD-transpeptidase enzyme. In
gram-negative bacteria, the transpeptidase creates a
covalent bond directly between peptidoglycan molecules, with
no intervening bridge.
Classification

In the original bacterial phyla, the Gram-positive organisms
made up the phylum Firmicutes, a name now used for the
largest group. It includes many well-known genera such as
Staphylococcus, Streptococcus, Enterococcus, (which are
cocci) and Bacillus, Corynebacterium, Nocardia, Clostridium,
Actinobacteria, and Listeria (which are rods and can be
remembered by the mnemonic obconical). It has also been
expanded to include the Mollicutes, bacteria-like Mycoplasma
that lack cell walls and cannot be Gram stained, but are
derived from such forms. Actinobacteria are the other major
group of Gram-positive bacteria, which have a high guanine
and cytosine content in their genomes (high G+C group). This
contrasts with the Firmicutes, which have a low G+C content.

Both Gram-positive and Gram-negative bacteria may have a
membrane called an S-layer. In Gram-negative bacteria, the
S-layer is directly attached to the outer membrane. In
Gram-positive bacteria, the S-layer is attached to the
peptidoglycan layer. Unique to Gram-positive bacteria is the
presence of teichoic acids in the cell wall. Some particular
teichoic acids, lipoteichoic acids, have a lipid component
and can assist in anchoring peptidoglycan, as the lipid
component is embedded in the membrane.


Gram Positive Classification.svg
Characteristics
Structure of gram-negative cell wall
Gram-positive- and negative bacteria are chiefly
differentiated by their cell wall structure.

The following characteristics are displayed by Gram-negative
bacteria:

Cytoplasmic membrane
Thin peptidoglycan layer (which is much thinner than in
Gram-positive bacteria)
Outer membrane containing lipopolysaccharide (LPS, which
consists of lipid A, core polysaccharide, and O antigen)
outside the peptidoglycan layer
Porins exist in the outer membrane, which act like pores
for particular molecules
There is a space between the layers of peptidoglycan and
the secondary cell membrane called the periplasmic space
The S-layer is directly attached to the outer membrane,
rather than the peptidoglycan
If present, flagella have four supporting rings instead
of two
No teichoic acids or lipoteichoic acids are present
Lipoproteins are attached to the polysaccharide backbone.
Most of them contain Braun's lipoprotein, which serves
as a link between the outer membrane and the peptidoglycan
chain by a covalent bound
Most do not sporulate (Coxiella burnetii, which produces
spore-like structures, is a notable exception)

Answer / puja singh

gram


gram -ve bacteria's wall is made up of phopholipid and a
thin layer of peptinoglygon is formed.

Phospholipid are absent in gram +ve bacteria's wall and a
thick layer of peptinoglycon is formed

Answer / sonali

Gram +ve bacteria Gram -ve bacteria

1)Presence of thick peptido- 1) presence of thin peptido-
glycan layer(80nn) glycan layer (2nm)
2)Techoic acid present. 2) Techoic acid absent.
3)Outer membrane absent. 3) outer membrane present.
4)Porin proteins absent. 4) porin proteins present.
5)lipoprotiens absent. 5) lipoproteins present.
6)Eg- Bacillus, Clostridium. 6) eg- salmonella, E.coli

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