Gram-negative
Gram-positive and Gram-negative describe the different staining behaviors of bacteria during Gram staining. This is caused by differences in the structure of their cell walls.
Detailed description
In Gram staining, bacteria are first stained with a purple dye. Gram-positive bacteria retain this dye even after the decolorization step and appear purple. Gram-negative bacteria, on the other hand, are decolorized and then become visible as pink to red after counterstaining. This difference in staining behavior is due to the structure of the cell wall: Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thin peptidoglycan layer and an additional outer membrane.
Gram staining allows for a quick preliminary classification of bacteria and can provide important information for diagnosis and the selection of appropriate antibiotic therapy in cases of infection.
