Purple or Pink? What Gram Staining Reveals About Bacteria

In microbiology, many techniques are essential, but few are as colorful and informative as the Gram stain. This technique is especially important because it helps categorize bacteria into two groups: Gram-positive and Gram-negative. Understanding this distinction is crucial for identifying bacterial species and determining appropriate treatments.

The Gram stain is achieved by using a series of dyes to highlight structural differences in the bacterial cell walls. When viewing under a microscope, Gram-negative bacteria will stain pink and Gram-positive bacteria will stain purple. The reasoning behind this is that Gram-positive bacteria have a thicker peptidoglycan layer holding onto the dye better than Gram-negative bacteria which lose their initial stain.

To efficiently Gram stain bacteria the following materials are needed:

• A bacterial sample

• Microscope

• Microscope

• Immersion oil

• Inoculating loop

• Bunsen burner

• Crystal violet

• Iodine

• Alcohol (decolorant)

• Safranin

• Bibulous paper

• Gloves

Step-by-step Gram-staining Procedure.

• Place a small drop of water onto the microscope slide and then smear a small amount of the bacterial sample onto it and spread out thinly on the slide

• Heat fix the microscope slide by passing it through the flame of the bunsen burner to attach the cells firmly onto the slide

• Apply crystal violet directly onto the slide for one minute and then wash gently with water

• Apply iodine directly onto the slide for one minute and then wash gently with water

• Decolorize with alcohol for no longer than 10 seconds

• Counter-stain with safranin for a minute then wash gently with water

• Use bibulous paper to gently blot the slide dry

• Observe sample using microscope
  

Real-World Relevance: Gram Staining and Antibiotic Resistance

https://pmc.ncbi.nlm.nih.gov/articles/PMC10226836/

You might wonder how Gram staining is relevant outside of lab work. A recent review published in 2023 highlights the growing problem of antibiotic resistance and why quick and reliable lab tests are important more than ever before. As bacteria evolve every day and resist the drugs used to treat them, doctors must find faster ways to identify infections and the bacteria associated with them in order to start the correct treatment before the bacteria spread and become harder to control.

This paper also emphasizes that the Gram stain is both essential and the most effective when used alongside other techniques, such as bacteria culturing and detecting resistance genes. Together, these techniques help clinicians and researchers help fight infections more efficiently and reduce the spread of antibiotic resistant microbes.