Megan Cunningham
4th Hour
Simple and Gram Stain Lab Report
Purpose/Introduction:
The purpose of the simple stain lab was to transfer bacteria onto a slide and
pour crystal violet on it so that we can see the bacteria more clearly through a
microscope. The crystal violet attaches onto the bacteria and creates a faint purple
to make it easier to see the bacteria. The purpose of this is to be able to recognize
the shape of the bacteria. The purpose of the gram stain lab was to find out the gram
response, meaning if it is positive (purple) or negative (red) and the shape of the
bacteria.
Procedure:
Simple Stain
1. Add a drop of H20 on the slide.
2. Sterilize the inoculating loop and let cool.
3. Grab the tiniest amount of bacteria with the inoculating loop.
4. Spread and mix the bacteria onto the slide with the inoculating loop.
5. Sterilize the inoculating loop.
6. Let the slide air-dry.
7. Heat fix the slide.
8. Add a large amount of crystal violet to the slide, completely covering the
bacteria.
9. Let the slide sit for a minute and a half.
10. Rinse of the slide with H2O.
11. Hold the slide up to the light and you should see a light purple flex.
Gram Stain
1. Follow steps 1-11 of Simple Stain procedure.
2. Add a large amount of grams iodine to the slide.
3. Let the slide sit for a minute.
4. Rinse the slide with H2O.
5. Decolorize the slide with ethyl alcohol.
6. Rinse the slide with H2O immediately.
7. Add a large amount of Safranin to the slide.
Megan Cunningham
4th Hour
8. Let the slide sit for a minute.
9. Rinse the slide with H2O.
Materials:
 Blank slides
 Bunsen burner
 Inoculating loop
 Water bottle
 Staining kit
 A block of stains
 Sharpie
 Clothes pins
 Bacteria
Data/Results:
BS- Gram Negative (Red)
BC- Gram Positive (Purple)
PF- Gram Positive (Purple)
SM- Gram Negative (Red)
MR- Gram Positive (Purple)
EC- Gram Negative (Red)
Conclusion:
If bacteria are gram positive then it has peptidoglycan in the outer cell walls,
so the crystal violet stays on the bacteria and the safranin doesn’t bind to it, causing
the bacteria to look purple. If bacteria are gram negative then the safranin binds to
the bacteria causing it to look red.