Gram negative

refers to the inability of a bacterium to resist decolorization with alcohol after being treated with Gram crystal violet

Description
Gram staining relies on retention in the bacterial cell wall. Although an important means of classifying bacteria, it has been superseded by more specific molecular methods for many purposes. Gram negative bacteria, following decolorization, can be readily counterstained with safranin, imparting a pink or red color to the bacterium when viewed by light microscopy, thus complementing the Gram-positive stain. However, many bacterial strains have been identified that stain with neither of the two methods, and other that vary in their stainability by either method. Gram-negative bacteria are generally more pathogenic than Gram-positive bacteria, due to their outer membrane structure. Lipopolysaccharide in their outer membrane may be broken down into the endotoxin Lipid A, which thus exacerbates the severity of the inflammatory reaction, possibly leading to septic shock. See Gram stain