Gram+ Stain of Staphylococcus @1000xTM

Gram Positive Bacteria
 Gram+ Bacterial Cell Wall Structure

Nearly all bacteria have a cell wall containing peptidoglycan, a chemical unique to bacterial cells. The rigid structure of the bacterial cell wall is due to securely linked peptidoglycan molecules that surround the cytoplasmic membrane, giving the prokaryotic 
bacterial cell shape and protection.

Gram-positive Cell Wall
From the peptidoglycan inwards all bacterial cells are very similar. 
Article Summary: Most bacteria have one of two types of cell walls. Here are the features of the Gram-positive bacterial cell wall that distinguish it from Gram-.

Gram-positive Bacterial Cell Wall
More Images of Gram-stained Bacteria Button

Instructor's Corner
Going further out, the bacterial world divides into two major classes: Gram positive (Gram +) and Gram negative (Gram -).

Gram Positive Bacteria, Staph. epidermidis @1000xTM
Gram-positive Staphylococcus epidermidis @ 1000xTM+
Comparison of Gram-positive and Gram-negative Cell Wall,  by Graevemoore on Wikipedia
In Gram-positive cells, peptidoglycan makes up as much as 90% of the thick cell wall; more than 20 layers of peptidoglycan 
stacked together. These layers are the outermost cell wall structure of Gram+ cells, whereas in Gram-negative cells, the thinner peptidoglycan component is covered by an external lipopolysaccharide (LPS) membrane.

The Gram Stain
Once scientists understood that infectious disease was caused by microorganisms (Germ Theory), it was imperative to find a way to view bacteria and other microbes; because in addition to being minute, most bacteria colorless.

In the 1800’s, Christian Gram, a Danish bacteriologist, developed a technique for staining bacteria that is still widely used today. The Gram stain protocol involves the application of a series of dyes that leaves some bacteria purple (Gram+) and others pink (Gram-). 

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​Page last updated: 11/2015
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Prokaryotic Cell, Mariana Ruiz
Has Christian Gram
H. C. Gram
Schematic of Gram Positive Bacterial Cell Wall Structure