Gram-Positive vs. Gram-Negative Basics
Gram-positive and gram-negative bacteria are classified using these terms. This distinction is based on the design of their cell walls and their sensitivity to Gram staining.
Gram-positive bacteria’s cell walls are thickly coated with peptidoglycan. Gram-negative bacteria get a thin peptidoglycan coating on their cell walls, but they also have an outer membrane, which gram-positive bacteria lack.
Gram staining is a technique that uses violet dye to differentiate between gram-positive and gram-negative bacteria. If the bacteria are gram-positive, the dye is absorbed by the thick peptidoglycan coating on their cell walls, resulting in a violet stain. If the bacteria are gram-negative, the dye will soak through the thin peptidoglycan coating, colouring them red.
What Are Bacteria?
Bacteria (singular: bacterium) are prokaryotic unicellular creatures that may be found in practically every place on the planet. Bacteria may be found in a wide variety of places, including soil, seas, hot springs, our homes, and perhaps our physical bodies. Many of them are safe or even useful. For example, the bacteria that live in the human gut (referred to as the gut microbiota) help digestion and may potentially prevent or treat some illnesses. Others (dubbed pathogens) are less hospitable and may cause illness.
There are millions of bacteria species on the planet. However, they may be classified into two categories depending on a particular trait: the way their cell walls are constructed.
Gram-Positive vs. Gram-Negative Bacteria
Gram-Positive Bacteria: In the cell wall, there is a thick peptidoglycan layer.
Gram-Negative Bacteria: In the cell wall, there is a thin peptidoglycan layer.
Gram-Positive Bacteria: There isn’t a lipopolysaccharide membrane.
Gram-Negative Bacteria: Membrane made of lipopolysaccharide
Gram-Positive Bacteria: Exotoxins are produced.
Gram-Negative Bacteria: Both Endotoxins and Exotoxins are produced.
Gram-Positive Bacteria: Gram-staining gave it a purple hue.
Gram-Negative Bacteria: Gram staining gave it a red/pink hue.
Cell Wall Structure in Gram-Positive vs. Gram-Negative Bacteria
Bacteria are grouped as gram-positive or gram-negative based on their cell wall structure.
Peptidoglycan is a substance present in the cell walls of the majority of bacteria (AKA murein). The peptididoglycan polymer is a massive polymer composed entirely of sugars and amino acids found only in bacteria. Gram-positive bacteria’s cell walls are covered in a thick, mesh-like layer of peptidoglycan. Gram-negative bacteria have a peptidoglycan coating on their cell walls, but also a lipopolysaccharide-based outer membrane. Bacteria classified as Gram-negative lack this outer membrane.
Toxins Produced by Gram-Positive vs. Gram-Negative Bacteria
Exotoxins as well as endotoxins are two distinct types of poisons generated by bacteria. Endotoxins, more usually referred to as lipopolysaccharides, are found in the outer membranes of gram-negative bacteria. Gram-positive bacteria are incapable of producing endotoxins because they lack an outer membrane.
Both gram-negative and gram-positive bacteria generate exotoxins, which are poisons released by bacteria.
What is Gram Staining and How Does it Work?
Gram staining is a typical method for determining whether bacteria are gram negative or gram positive. It was named after Hans Christian Gram, a Danish bacteriologist who invented the procedure in 1882.
Gram staining includes using a crystal violet dye to stain a sample of bacterial cells, preceded by a solution of Gram’s iodine (consisting of iodine and potassium iodide). The sample is then treated with a decolorizer (like ethyl alcohol or acetone). The peptidoglycan layer in bacterial cell walls shrinks and tightens as a result of this dehydration. The crystal violet dye is bound inside the gram-positive bacteria’s thick peptidoglycan covering. Gram-negative bacteria’s weak peptidoglycan layer is unable to retain the dye, which leaks out of the cell wall.
The microorganisms are then examined through a microscope. The gram-positive or gram-negative status of the cells is determined by the colour of the cells following staining.
Gram Staining Results in Gram-Positive vs. Gram-Negative Bacteria
If bacteria are gram-positive, the Gram staining technique will turn them violet. This is because the crystal violet dye is held in their cell walls by a thick, mesh-like covering of peptidoglycan. Because the crystal violet dye does not adhere to the thin peptidoglycan walls of gram-negative bacteria during the decolorizing procedure, the dye tints them crimson or pink.
