Gramnegatívek

Gramnegatívek is a term used in microbiology to describe bacteria that do not retain the crystal violet stain during the Gram staining procedure. This is a differential staining technique used to classify bacteria into two large groups based on their cell wall composition. Gram-negative bacteria, unlike Gram-positive bacteria, have a complex cell wall structure that includes a thin layer of peptidoglycan and an outer membrane rich in lipids.

When subjected to the Gram stain, Gram-negative bacteria are decolorized by alcohol or acetone, and thus they do not appear purple or blue under the microscope. Instead, they take up the counterstain, typically safranin, and appear pink or red. This distinction is crucial for identifying and classifying bacteria, as it often correlates with differences in their pathogenicity, antibiotic susceptibility, and other biological characteristics.

Many common and clinically significant bacteria are Gram-negative, including members of the genera Escherichia, Salmonella, Shigella, Pseudomonas, and Neisseria. The presence of the outer membrane in Gram-negative bacteria acts as a barrier, making them inherently more resistant to certain antibiotics and host immune responses compared to Gram-positive bacteria. Understanding the Gram stain classification is a fundamental step in diagnosing and treating bacterial infections.