THE CELL WALL AND THE GRAM REACTION

Abstract

The Gram reaction of yeast and bacterial cells is due to, and influenced by, the same factors in each. After the cell is crushed and the protoplasm extruded, the empty sac can be seen. Both are unstained after exposure to the Gram stain. The breaking of the cell wall causes the protoplasm of Gram-positive bacteria and of yeast cells to become Gram-negative. The protoplasm within intact cells and the extruded protoplasm may have the same Ph and stain differently. The extruded protoplasm can not be made Gram-positive. Acid and alkali readily penetrate the cell wall. They interfere with the Gram reaction by affecting the passage of the dye-iodine precipitate through the cell wall. They alter the affinity between dye and protoplasm but this is not part of the Gram reaction, though it may interfere with it to a minor extent. The function of the mordant in the Gram technique is that of a precipitating agent; the precipitate must be insoluble in water, soluble in the decolor-izer. It must less readily pass through the cell wall of the Gram-positive organisms. The precipitation of the dye results in the losing of its affinity for the protoplasm. The affinity of the aqueous gentian violet for both Gram-negative and Gram-positive bacteria or the extruded protoplasm can be increased by H2O2 and alkali. Protoplasm so treated resists decolorization. This reaction has been confused with the true Gram reaction. It is nullified by the action of Gram''s iodine. The authors designate this reaction as the pseudo-Gram reaction. Any factor that alters the cell wall or the dye-iodine-precipitation may affect the Gram reaction. Bacteria are Gram-positive, Gram-negative or Gram-variable depending on the permeability of the cell wall.