Question

Briefly discuss how the Gram stain works, Not the steps but the biochemical basis, what leads to the differential staining? Name one organism (genus and species) that is a Gram positive coccus, and one that the Gram stain will not work on.n

Answer 1

Gram staining differentiates Gram positive cells and Gram negative cells on the basis of their cell wall properties

Gram positive cells have a thicker peptidoglycan layer in their cell wall so they retain the primary stain of crystal violet which froms complex with iodide as compared to thin layer of peptidoglycan in Gram negative bacteria in which the primary stain is washed out and they take up secondary stain (safranin)

Gram positive-Streptococcus pyogens

Gram negative-Salmonella typhimurium