Histochemistry of the Gram-staining reaction for micro-organisms

Extraction of certain Gram -positive micro-organisms with a 2% solution of a bile salt (preferably sodium cholate) strips the cell of an essential part of its dye-retaining constituent leaving a Gram-negative cytoskeleton. From the bile-salt extract there was separated a fraction which could be plated back on suitably reduced cytoskeletons and thereby restore in a large measure the Gram-positive character of the cell. The essential agent in the extract was magnesium ribonucleate, and it is considered that the Gram-positive or dye-retaining constituent is a nucleoprotein formed by the combination of ribonucleic acid with a basic protein in the cytoskeleton. The stripping and replating processes could be demonstrated by photomicrographs taken in ultra-violet light.