Bacterial Morphology and Gram Staining

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Bacterial Morphology and Gram Staining
Introduction
Gram staining technique is a biological lab method used to classify two distinct groups of bacteria. The differentiation is based on the components of the bacterial cell wall. In this case, the Gram stains differentiate between the Gram-Positive and Gram-negative through red and violet coloring of the cells. The existence of peptidoglycan cell membrane in the bacteria is a significant aspect that facilitates the classification of the bacteria as either the Gram-negative or Gram-positive type of bacteria. In the case of Gram-positive bacteria, they have a dense layer of peptidoglycan cell membrane which is the primary cause of violet stains during this process. Gram-negative bacterium, however, has a skinny layer of peptidoglycan in its cell membrane which is the primary cause of red stains. In this case, the size of the peptidoglycan structure in the cell walls of the bacteria is the main distinguishing factor in the Gram Staining procedure (Bottone, 288-290).
Methods
The Gram Staining technique is based on four basic steps which result in the classification of different types of bacteria based on their cell morphology. The primary steps in this technique are as follows;
Application of crystal violet (CV), the primary stain. This is the first step in the Gram Staining process. The aqueous solution of the CV dissociates into Cl- and CV ions. Then, these ions penetrate the cell membrane of the cells.

In the process, the CV+ ions interrelate with the bacterial constituents which are negatively charged, and as a result, the bacteria cells are stained purple.
Gram’s Iodine addition. The Gram’s Iodine solution is used as a trapping agent and at the same time as a mordant: a solution that increases the affinity of the cell wall to staining through the formation of an insoluble complex in the cell wall. As the crystal violet reacts with Iodine, it forms an insoluble complex which turns the cells purple.
De-colorization with ethyl alcohol or acetone. This is the third step in the Gram Staining process. The purpose of using the ethyl alcohol or acetone is to decolorize the cell sample if it is Gram negative. This happens through the removal of crystal violet from Gram-negative cells by the ethyl alcohol or acetone.
Safranin counterstaining. This is the final stage of the Gram staining procedure. Safranin is used to make the decolorized Gram-negative cells more visible through pink staining of the cells. A positively charged safranin is responsible for the pink stains in the Gram-negative bacteria cells.
Results
From these pictures, there are two different images with stains of different colors. One image contains a sample of a bacteria with dark purple stains which is a result of the crystal violet color retained in the bacteria cell walls. The other image contains red and pink stains as a result of the safranin staining dye. As stated earlier, the dark purple stains belong to the Gram-positive bacteria whereas the pink and red stains are the Gram-negative bacteria. In this case, the Staphylococcus bacteria belongs to the Gram-positive bacteria whereas the Escherichia coli belongs to the Gram-negative bacteria (Microbiology Virtual Lab, n.pag). The Staphylococcus aureus bacteria are arranged in a grape-like shape with irregular cell divisions. On the other hand, Escherichia coli has a rod-shaped figure.
Discussion
The Gram-negative bacteria contain a complex cell wall structure that is relatively different from the Gram-positive bacteria. In these bacteria, the peptidoglycan cell wall is positioned in between the outer membrane of the bacteria and the inner cytoplasmic membrane. The bacteria outer membrane protects the cell from common antibiotics that can be destructive to the peptidoglycan membrane. Additionally, the lipopolysaccharide (LPS) is a complex lipid structure in the bacterial cell wall that plays the role of an endotoxin which causes a toxic reaction that aims at destroying the immune cells of the human body. With these characteristics attributed to the complex cell wall structure of the Gram-negative is highly resistant to antibiotics, as such, it leads to the continuous spread of diseases. (Paterson, 23-24).
Work Cited
“Gram Stain Technique.” Gram Stain Technique (Theory): Microbiology Virtual Lab I: Biotechnology and Biomedical Engineering: Amrita Vishwa Vidyapeetham Virtual Lab, vlab.amrita.edu/?sub=3&brch=73&sim=208&cnt=1.
Bottone, Edward J. “The gram stain: the century-old quintessential rapid diagnostic test.” Laboratory Medicine 19.5 (2016): 288-291.
Paterson, David L. “Resistance in gram-negative bacteria: Enterobacteriaceae.” The American journal of medicine 119.6 (2006): S20-S28.