MBK – Lab Report Name: Brittany
Klinkel Section:
MHD-B2
Differential Staining
Part 2: Differential Staining
Record your observations.
We were able to clearly see the color differences between gram-positive and
gram- negative cells. The gram-positive cells were purple in color and the
gram-negative cells were more pink/red or even colorless with the
alcohol. I could see the thick cell wall in the gram-positive stain. The
gram-positive slides always appeared to be in clusters together and
remained purple. The gram-negative slide also remained in small clusters.
Questions:
A. What is a differential stain? How is it different from a simple stain?
A differential stain is the stain that is used to differentiate one component or
cellular structure from another, or to differentiate an entity from another in
a specimen. It does so by coloring a portion of a specimen (e.g. of a tissue
or of a cell) that remained uncolored following the first staining using a dye
of different color.
Simple staining is staining with only one dye/stain.
B. What is the difference between gram-positive and gram-negative cell
walls?
Gram-positive cell walls are much thicker and gram-negative cell walls are
much thinner.
C. What is the purpose of crystal violet in the Gram’s stain procedure?
The purpose of crystal violet in the Gram’s stain procedure is to dye the
bacteria sample. The crystal violet increases the contrast of both gram-
positive and gram- negative bacteria and makes them appear purple.
D. What is the purpose of iodine in the Gram’s stain procedure? (What is
a mordant?)
Klinkel Section:
MHD-B2
Differential Staining
Part 2: Differential Staining
Record your observations.
We were able to clearly see the color differences between gram-positive and
gram- negative cells. The gram-positive cells were purple in color and the
gram-negative cells were more pink/red or even colorless with the
alcohol. I could see the thick cell wall in the gram-positive stain. The
gram-positive slides always appeared to be in clusters together and
remained purple. The gram-negative slide also remained in small clusters.
Questions:
A. What is a differential stain? How is it different from a simple stain?
A differential stain is the stain that is used to differentiate one component or
cellular structure from another, or to differentiate an entity from another in
a specimen. It does so by coloring a portion of a specimen (e.g. of a tissue
or of a cell) that remained uncolored following the first staining using a dye
of different color.
Simple staining is staining with only one dye/stain.
B. What is the difference between gram-positive and gram-negative cell
walls?
Gram-positive cell walls are much thicker and gram-negative cell walls are
much thinner.
C. What is the purpose of crystal violet in the Gram’s stain procedure?
The purpose of crystal violet in the Gram’s stain procedure is to dye the
bacteria sample. The crystal violet increases the contrast of both gram-
positive and gram- negative bacteria and makes them appear purple.
D. What is the purpose of iodine in the Gram’s stain procedure? (What is
a mordant?)
