What is the Gram staining reaction of Escherichia coli?

What is the Gram staining reaction of Escherichia coli?

• A. Gram-positive
• B. Gram-negative
• C. Gram-variable
• D. Non-stained

Answer: (B)

Escherichia coli is classified as a Gram-negative bacterium, which is characterized by its thin peptidoglycan layer and the presence of an outer membrane containing lipopolysaccharides. In the Gram staining process, when subjected to the crystal violet dye, the cells retain the violet color, but subsequent treatment with iodine, alcohol, and safranin results in a loss of the initial stain due to the structural properties of the Gram-negative cell wall. Consequently, when the final dye (safranin) is applied, these bacteria exhibit a pink or red coloration. This distinguishing feature is essential in microbiology for identifying and differentiating bacterial species and informs decisions regarding treatment and understanding pathogenic mechanisms. The Gram-negative characteristic of E. coli is central to its classification and behavior in clinical settings.

Escherichia coli is classified as a Gram-negative bacterium, which is characterized by its thin peptidoglycan layer and the presence of an outer membrane containing lipopolysaccharides. In the Gram staining process, when subjected to the crystal violet dye, the cells retain the violet color, but subsequent treatment with iodine, alcohol, and safranin results in a loss of the initial stain due to the structural properties of the Gram-negative cell wall. Consequently, when the final dye (safranin) is applied, these bacteria exhibit a pink or red coloration. This distinguishing feature is essential in microbiology for identifying and differentiating bacterial species and informs decisions regarding treatment and understanding pathogenic mechanisms. The Gram-negative characteristic of E. coli is central to its classification and behavior in clinical settings.