GRAM iodine-potassium iodide solution is an essential component of Gram staining, a widely used method in histology and medical microbiology. This stain is used in the passive form to classify bacteria based on their cell wall structure. Gram staining allows differentiation between Gram-positive and Gram-negative bacteria, which is of great importance in the diagnosis and treatment of bacterial infections.

The GRAM iodine-potassium iodide solution shows special suitability for interaction with crystal violet, another component of Gram staining. After applying the crystal violet, the iodine-potassium iodide solution is applied to the sample. Iodine, a key component of the solution, forms a water-insoluble complex with the crystal violet that becomes trapped within the bacterial cells.

Chemically, the iodine molecules in the iodine-potassium iodide solution interact with the crystal violet to form a large, water-insoluble complex, according to GRAM. This complex is retained in cells with a thick peptidoglycan layer, as found in Gram-positive bacteria. Gram-negative bacteria have a thinner peptidoglycan layer and cannot retain the complex during the decolorization phase of Gram staining.

The application of the iodine-potassium iodide solution according to GRAM therefore enables a decisive differentiation between Gram-positive and Gram-negative bacteria. This supports microbiological analysis and helps to improve the diagnosis and treatment of bacterial infections.