Ribonucleic Acid and the Gram Stain

Abstract

The outer layer of gram-positive organisms contains, in addition to carbohydrates and proteins, considerable amounts of ribonucleic acid. This material in combination with Mg and the cell protein is responsible for the gram-positive staining reaction. The apparent difference in size between gram-positive and gram-negative forms of the same organism is due, not to the precipitation of the gram reagents, but to the visibility of the outer layer. The purpose of the iodine in the gram stain is apparently a reaction with sulfhydryl groups.