Gram Staining Essay

Introduction

Staining is used in a variety of ways in order to color the background of a cell, discern types of cells and to discern structures of a cell. A differential stain is when multiple dyes are used to stain a cell that take advantage of chemical differences in a cell. Gram staining is a type of differential stain that works by distinguishing gram positive and gram negative cells by coloring them violet or red, respectively. Gram positive cells contain a thick cell wall of peptidoglycan and a single membrane. Gram negative cells contain a thin cell wall which is located between two membrane layers. There are four reagents used in gram staining which include crystal violet, iodine, ethanol and basic fuchsin. Crystal violet is a primary methyl

Iodine is a mordant that binds the crystal violet to the cell. Ethanol is a decolorizer that in gram negative, washes away outer membrane and cell wall and in gram positive, collapses the cell wall. Basic fuchsin is counterstain that enters the unstained gram negative cells. Gram staining is a useful method as it is simple and inexpensive to perform and it gives important identification information about bacterial cells fairly quickly. One drawback to gram staining is that some cells can be gram variable because the age of the culture can influence the results. When cells are gram variable, it is difficult to tell if the culture is contaminated, or just old. Gram staining was devised in 1882 and published in 1884 by Danish bacteriologist Hans Christian Gram. In the medical field, gram staining can be used on bodily fluids to determine if there is a