What is the expected result of Gram staining on Gram negative bacteria?

The expected result of Gram staining on Gram-negative bacteria is that the cell wall will be stained reddish after the process. This occurs due to the structural differences in the cell wall composition of Gram-negative bacteria compared to Gram-positive bacteria.

Gram-negative bacteria possess a thin layer of peptidoglycan surrounded by an outer membrane. During the Gram staining process, the crystal violet dye initially penetrates the cells, but in the decolorization step, the outer membrane is disrupted, allowing the dye to leak out. After the decolorization, a counterstain, usually safranin, is applied. This counterstain stains the decolorized Gram-negative cells, resulting in a reddish appearance.

In contrast, Gram-positive bacteria retain the crystal violet and appear purple due to their thick peptidoglycan layers. Thus, the unique structure of Gram-negative bacteria can be clearly observed through the Gram staining technique, leading to their characteristic reddish color after the procedure.