Gram-positive bacteria have thick cell walls. A Gram stain test, which involves a chemical dye, stains the bacterium’s cell wall purple. On the other hand, gram-negative bacteria stain pink instead.

Gram staining is one way scientists can identify bacteria. Gram-positive bacteria, such as Staphylococcus, appear blue or purple under a microscope when scientists apply a stain. Conversely, ...

If your doctor suspects you have an infection, they may order a culture and gram stain to check for bacteria. If bacteria are present, this test can also help your doctor learn if the bacteria are ...

With delicate hues of purple and pink, a lab technique called gram staining has reliably characterized bacteria for more than a century. Yet many scientists are mistaken about why the vivid method ...