Chapter 3, Problem 1A

Summary Introduction

To write:

The omitted step in a Gram stain method that allow differentiation of Gram-positive and Gram-negative cells.

Given:

“Gram stain” “differentiation “and “omitted step”

Introduction:

In 1884, the Danish scientist Hans Christian Joachim Gramis discovered the Gram staining procedure to differentiate the bacteria into two groups, Gram-positive and Gram-negative. It is the preliminary step to identify the staining characteristics of bacteria based on the morphology and arrangement, which is observed under the light microscope.

The main principle of Gram stain is used to differentiate based on the color retaining ability of the stain. Gram-positive bacteria retains crystal violet and appears violet or purple in color under the microscope. Since, the cell wall of Gram-positive bacteria contain thicker peptidoglycan layer. So, it retains the stain during ethanol decolonization step. Whereas in the Gram-negative with thinner peptidoglycan layer denatured during ethanol step and retains the secondary stain (safranin) and appears pink color under the microscopic examination.