Gramnegatiivisuus

Gramnegatiivisuus refers to a characteristic of bacteria that causes them to stain pink or red in the Gram staining procedure. This staining property is due to the composition of their cell wall. Gram-negative bacteria possess a thin peptidoglycan layer located outside the cytoplasmic membrane, and this thin layer is surrounded by an outer membrane containing lipopolysaccharides. During the Gram stain, the crystal violet stain is readily decolorized from the thin peptidoglycan layer by alcohol or acetone. The counterstain, safranin, then stains the bacteria pink or red.

This difference in cell wall structure between Gram-positive and Gram-negative bacteria has significant implications. The outer membrane of Gram-negative bacteria acts as a barrier, providing resistance to certain antibiotics and detergents. This structural difference also influences the types of infections Gram-negative bacteria can cause and how they are treated. Many common pathogens, such as Escherichia coli, Salmonella, and Pseudomonas aeruginosa, are Gram-negative. Understanding Gram-negativity is fundamental in microbiology for bacterial identification, classification, and the development of effective antimicrobial therapies. The presence of lipopolysaccharides in the outer membrane, in particular, can trigger potent immune responses in the host.