In this simplified diagram of gram staining, bacterial cells are first treated with a purple dye called crystal violet. The dye gets into the cells’ peptidoglycan layer (gray), tinting it purple.

Most species of bacteria can be broadly divided into two groups, known as gram-positive and gram-negative. These categories ...

The term “Gram” refers to a specimen staining method developed by Hans Christian Gram in 1884. It involves staining an organism with crystal violet or methylene blue dye and then observing the ...

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.

Conversely, Gram-negative bacteria do not hold the dye well. Gram-negative bacteria may appear red under the microscope because red-pink iodine is used alongside the Gram stain as a control.

The Gram staining was first developed by a Danish scientist, Christian Gram, in 1884 and it has been used so far as the golden standard to classify bacteria. However, it has several obstructions.

Gram staining is a type of differential staining used to distinguish between gram positive and gram negative bacterial groups. ... before being counterstained with the red dye, safranin.

Being a cationic dye, crystal violet can be used to stain negatively charged polymers such as DNA 18 and cell walls of bacteria, the latter of which is partially the basis of Gram staining to ...