Why is gram staining not usually applied to eucaryotes?

Answer 1

Gram staining is commonly used on prokaryotic bacteria to determine if their cell wall is gram negative or gram positive. Their cell wall is made of peptidoglycan. It responds well and is stained in certain ways depending on the structure (wether it's gram positive or negative).

Animal eukaryotic cells don't even have a cell wall to be stained. In the case of eukaryotic plant cells, that do have cell walls, their cell wall is not made of peptidoglycan. In any case, there is no such thing as gram positive, or gram negative, cell walls in eukaryotes. There would be no point in the test, since it's specifically designed for prokaryotic cells.

Answer 2

Human cells cannot be successfully Gram Stained, because they have no cell wall. The purple colouring of the stain just washes out of human cells.

Normally, the iodine reacts with the peptidoglycan in the bacteria's cell wall. This means that the crystal violet is not washed out. Human cells only have a plasma membrane, so the colour washes out. This means that the Grain stain would have a negative result, even if the nuclei retains some colouring.

Answer 3

Gram staining is not usually applied to eukaryotes because the cell walls of eukaryotic cells lack the peptidoglycan layer that the Gram stain targets. Instead, eukaryotic cells have complex membrane structures that are not effectively stained by the Gram technique. Gram staining is more commonly used to differentiate between different types of bacteria based on the differences in their cell wall composition.