What is gram staining bacteria?

Gram staining is a laboratory technique used to differentiate bacterial species into two groups based on the characteristics of their cell walls. The technique is named after its inventor, Hans Christian Gram, who developed the method in 1884.

In the Gram staining process, bacterial cells are first stained with crystal violet, then treated with iodine, which forms a complex with the crystal violet. The cells are then washed with alcohol or acetone, which causes the cells to either retain or lose the crystal violet-iodine complex. Finally, the cells are counterstained with safranin, which stains the cells that have lost the crystal violet-iodine complex.

Bacteria that retain the crystal violet-iodine complex after washing with alcohol or acetone are called gram-positive bacteria and appear purple under a microscope. Bacteria that lose the crystal violet-iodine complex and take up the safranin counterstain are called gram-negative bacteria and appear pink or red under a microscope.