Gram staining Flashcards
1
Q
Briefly outline the gram staining method
A
1) Stain bacterial slides with crystal violet and wash with water
2) Flood with Gram’s iodine
3) Wash with water and alcohol until no further colour loss
4) Add safranin
5) Blot and dry slide
2
Q
What is safranin?
A
A counterstain
3
Q
What colour will Gram positive bacteria be? Why?
A
Violet
Thick peptidoglycan wall which binds to crystal violet
Safranin has no effect
4
Q
What colour will Gram negative bacteria be? Why?
A
Pink
Thinner peptidoglycan wall covered by a liposaccharide layer
Alcohol washes away crystal violet
Safranin stain gives pink colour
