MICROBIOLOGY
GRAM-STAIN
1
, Stain
Definition Stain :Impregnation of a specimen
with coloring materials that makes the structure
visible under microscope is called staining.
Staining is done to see the morphology and
staining reaction of bacteria.
2
,Types of Stain :
ii. Differential stains : differentiates
different groups of organisms
– Gram stain
– Acid fast stain
– Albert’s stain
iii.Special stains: normally not done.
-Capsular
-Flagellar stains
-spore stains
-Stain with acridine orange etc. 3
, Gram stain
• Gram positive Bacteria : violet colour
• Gram negative Bacteria: red colour
4
, Differential Staining
• divides microorganisms into groups based on
their staining properties
– e.g., Gram stain
– e.g., acid-fast stain
• Steps of Gram staining
• Primary stain = crystal violet
• Mordant = iodine
• Decolorization by ethanol
• Counterstain = safranin
5
, Gram Stain
6
GRAM-STAIN
1
, Stain
Definition Stain :Impregnation of a specimen
with coloring materials that makes the structure
visible under microscope is called staining.
Staining is done to see the morphology and
staining reaction of bacteria.
2
,Types of Stain :
ii. Differential stains : differentiates
different groups of organisms
– Gram stain
– Acid fast stain
– Albert’s stain
iii.Special stains: normally not done.
-Capsular
-Flagellar stains
-spore stains
-Stain with acridine orange etc. 3
, Gram stain
• Gram positive Bacteria : violet colour
• Gram negative Bacteria: red colour
4
, Differential Staining
• divides microorganisms into groups based on
their staining properties
– e.g., Gram stain
– e.g., acid-fast stain
• Steps of Gram staining
• Primary stain = crystal violet
• Mordant = iodine
• Decolorization by ethanol
• Counterstain = safranin
5
, Gram Stain
6
