Gram Staining
Gram staining is used to identify different types of bacteria based on their cell wall. Specifically, the amount of peptidoglycan in the cell wall. There are two main groups from gram staining: Gram positive and Gram negative. Through gram staining, we are able to classify bacteria into one of the two groups.
When a bacteria is stained purple after gram staining, it is Gram positive. This tells us that the bacteria has thin cell walls with a lot of peptidoglycan. Gram positive cell walls contain a lot of protein.
Gram negative bacteria will turn up as red or pink in color. This tells us that the bacteria has thick cell walls with only a thin layer of peptidoglycan. On these types of bacteria, there is a thick liposaccharide layer, meaning that these bacteria contain little protein but a lot of fats and sugars.
The reason bacteria show up as either purple or red is because of the peptidoglycan in their cell walls. The initial stain of Crystal violet adheres to the peptidoglycan and stains it. When the bacteria is rinsed with alcohol, the crystal violet will rinse off if there is a little amount of peptidoglycan in the cell walls. Then, with the counter stain of safranin, bacteria with little peptidoglycan will stain a red color. Bacteria with a lot of peptidoglycan is already stained from the crystal violet and it will not be rinsed off or stained by the safranin.
When a bacteria is stained purple after gram staining, it is Gram positive. This tells us that the bacteria has thin cell walls with a lot of peptidoglycan. Gram positive cell walls contain a lot of protein.
Gram negative bacteria will turn up as red or pink in color. This tells us that the bacteria has thick cell walls with only a thin layer of peptidoglycan. On these types of bacteria, there is a thick liposaccharide layer, meaning that these bacteria contain little protein but a lot of fats and sugars.
The reason bacteria show up as either purple or red is because of the peptidoglycan in their cell walls. The initial stain of Crystal violet adheres to the peptidoglycan and stains it. When the bacteria is rinsed with alcohol, the crystal violet will rinse off if there is a little amount of peptidoglycan in the cell walls. Then, with the counter stain of safranin, bacteria with little peptidoglycan will stain a red color. Bacteria with a lot of peptidoglycan is already stained from the crystal violet and it will not be rinsed off or stained by the safranin.