What Is the Difference Between Gram Positive and Gram Negative?

By Staff WriterLast Updated Mar 25, 2020 2:27:50 AM ET

Differences between Gram positive and Gram negative bacteria include the thickness of the cell wall, which is approximately 20 to 30 nanometers thick in Gram positive and 8 to 12 nanometers thick in Gram negative; the amount of peptidoglycan in the cell walls; and the lipid and lipoprotein content, which is low in Gram positive bacteria and high in Gram negative. Using the Gram staining process, Gram positive bacteria results in a purple hue, while Gram negative results in pink.

All bacteria contain a layer of peptidoglycan in their cell wall, but the difference between Gram positive and Gram negative bacteria is that Gram negative has a thin layer of peptidoglycan located between two lipid layers. This is what gives Gram positive bacteria a pink or red stain in the Gram staining process. Gram positive bacteria, on the other hand, results in a violet or purple hue because of the thick layer of peptidoglycan located in their cell walls. The Gram staining process, discovered by Hans Christian Gram, helps identify bacteria.

Another difference between Gram positive and Gram negative bacteria is in the structure of the flagella, with Gram positive containing two rings in basal body, and Gram negative containing four rings in the basal body. Gram positive bacteria has a high susceptibility to penicillin and sulfonamide treatments, while Gram negative bacteria has a low susceptibility.