How to gram stain

How to gram stain


  • DI water
  • Sterile loop
  • Slide Warmer
  • Bunsen Burner
  • Close pin 
  • Crystal Violet
  • Gram Iodide
  • Ethonal
  • Safranin
  • Slides
  • Plastic container
  • Trash bucket
Gram stain by me is licensed under CC BY 2.0
Materials by me are licensed under CC BY 2.0
Slide warmer by me is licensed under CC BY 2.0




Culture by me is licensed under CC by 2.0






To gram stained a culture, pour a drop of DI water on a slide. Then with a sterile loop,  loop some of the cell from the pure colony on the plate and mixed it in with the water on the slide; remember to spread it out to make it dry quicker. After, place the slide on a slide warmer to dry for a few minutes. When the slide is dry on the slide warmer, pass the slide through the fire with a close pin using a bunsen burner about 3 times quickly to heat fix. Now, placed the slides in a plastic container to begin the dying process. Drop a few crystal violets on the slide; enough to cover the slide and waited 1 min before washing it off with DI water. After a min washed off the slide and then apply gram iodide, which binds to crystal violet and traps it in the cell. After another min washed off the iodide with ethanol for rapid decolorization. Then rinse the slide off with water and add safranin on it for another min. After a min, wash off the safranin with DI water and placed the slide on a paper towel to dry off the excess water. After lightly damping the top of the slide with a paper towel, place the slide under a microscope to look at the color of the cells to observe if its a gram negative or positive. Gram-negative bacteria will appear pink under a microscope while gram-positive bacteria will appear purple. 


Photo by me is licensed under CC BY 2.0

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