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Gram Positive vs. Gram Negative Bacteria



Bacteria have cell walls made up of polysaccharides that give them strength and rigidity. This is important since bacteria often experience variations in osmotic strength from solutions of their environment, and their cell walls prevent them from shrinking or swelling. As a reminder, osmosis is the process by which solvent molecules pass through a semipermeable membrane from a less concentrated solution to a more concentrated one, equalizing the concentration on either side of the membrane. Nearly all bacterial cell walls have a peptide-polysaccharide layer called peptidoglycan, or sometimes murein. Peptidoglycan is a polymer made up of sugars and amino acids which forms a kind of mesh.
Bacteria can be classified based on their reaction to the Gram stain, which identifies them based on the chemical and physical properties of their cell walls, as gram positive or gram negative. Gram positive bacteria have a thick cell wall, which consists of up to around 30 layers of peptidoglycan. This cell wall surrounds a monoderm, which is a single plasma membrane. Gram negative bacteria have a MUCH thinner cell wall, consisting of a single layer of peptidoglycan. This layer of peptidoglycan is sandwiched between two lipid bilayer membranes called diderms.
We can differentiate between gram positive and gram-negative bacteria by dying them with crystal violet and then washing them with a decolorizing solution. Then, a counterstain is added, for example safranin or fuchsine. Gram positive bacteria will retain the crystal violet dye and remain purple, while the gram-negative bacteria will be stained pink. Note that gram positive bacteria also pick up the pink colour of the counterstain, however this is not visible when they are dyed with the darker purple colour of the crystal violet stain.
The reason for these staining differences is due to differences in cell wall structure, which is the chief difference between gram positive and gram-negative bacteria. The gram stain detects peptidoglycan, and since Gram positive bacteria have a thick, multilayered peptidoglycan layer, they retain the crystal violet dye. Gram-negative bacteria do not retain the dye for two reasons – they have an outer membrane getting in the way of the crystal violet and they lack peptidoglycan to retain the stain.
Although both gram positive and gram-negative bacteria can be pathogenic, gram negative bacteria are more resistant to antibodies because of their impenetrable cell wall. Unfortunately, these bacteria also develop resistance more quickly.
Not all bacteria can be reliably classified through Gram staining. Acid-fast bacteria or Gram-variable bacteria for example, do not respond to Gram staining. Acid-fast bacteria have cell walls that retain stains particularly well. Although they aren’t closely related to gram-positive bacteria, they can appear purple after the gram stain test. Gram-variable bacteria show a mix of pink and purple cells when stained.

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Gram Positive vs. Gram Negative Bacteria

This video highlights the similarities and differences between Gram positive and Gram Negative bacteria. The process of a Gram Stain is also discussed.

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Plasma Membrane
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Gram Positive Bacteria vs Gram Negative Bacteria

Biology Professor (Twitter: @DrWhitneyHolden) describes the major differences in Gram-Positive bacteria cell walls and Gram-Negative bacteria cell walls, including peptidoglycan layers, inner wall zones and periplasm, plasma and outer membranes, lipopolysaccharide (LPS), and lipoteichoic acids. Common examples of both Gram-Positive bacteria and Gram-Negative bacteria are also described. Great for MCAT Biology Review! For more information on how Gram-Positive and Gram-Negative Bacteria are distinguished under a microscope using a Gram Stain, see Biology Professor's video:

Gram Positive vs Gram Negative Bacteria - Gram Staining Technique

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Microbiology lecture 2 | Gram positive and Gram negative bacteria Gram staining principle

Microbiology lecture 2 | Gram positive and Gram negative bacteria Gram staining principle - This second microbiology lecture will explain the properties of Gram positive and Gram negative bacteria. It also explains the differences in characteristics of Gram positive and Gram negative bacteria. You will learn the cell wall structure of bacteria and the cell wall structure of Gram negative bacteria and Gram positive bacteria.
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Bacterial Cell Envelope, Gram Positive and Gram Negative Bacteria

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List of Gram-positive Bacterial and Gram-Negative Bacteria - Microbiology with Sumi

Here in this video, I have given some examples and a list of Gram-positive and Gram-Negative bacteria.
#Grampositivebacteria #Gramnegativebacteria #Microbiology

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Dr Mike explains the differences between gram +ve and gram -ve bacteria and how we exploit these differences clinically.

Difference between Gram Positive and Gram Negative Bacteria

This video explains:
Difference between Gram Positive and Gram Negative Bacteria
Why the name gram staining?
Cell wall of gram positive and gram negative bacteria
How gram stain works?

For more:
Gram staining step wise procedure

Gram Positive vs Gram Negative Bacteria

Example of Gram Positive Bacteria

Example of Gram Negative Bacteria

Gram positive Vs Negative

General microbiology discussion

Lecture -#53 - Gram Positive and Gram Negative Bacteria /Difference In Hindi

Hello friends in this lecture explained about Gram positive and gram negative bacteria, difference in hindi or difference between gram positive and gram negative bacteria. there is the comperision between gram positive vs gram negative bacteria.gram positive and gram negative bacteria में अंतर बताया गया है! there is also explanation about difference between gram positive and gram negative bacteria on the basis of gram staining.
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Mnemonics for gram positive and gram negative bacteria | Gram positive and negative bacteria |

This video lecture describes the simple mnemonics for remembering the complex list of Gram positive and Gram negative bacteria.
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Mnemonics for Remembering Gram Positive & Gram Negative Organisms

In this video, I will be discussing various mnemonics on easily remembering various Gram positive & negative cocci and bacilli.

Differences Between Gram Positive and Gram Negative Bacteria

Gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their cell wall.

Gram-positive bacteria take up the crystal violet stain used in the test, and then appear to be purple-coloured when seen through a microscope. This is because the thick peptidoglycan layer in the bacterial cell wall retains the stain after it is washed away from the rest of the sample, in the decolorization stage of the test.

Gram-negative bacteria cannot retain the violet stain after the decolorization step; alcohol used in this stage degrades the outer membrane of gram-negative cells, making the cell wall more porous and incapable of retaining the crystal violet stain. Their peptidoglycan layer is much thinner and sandwiched between an inner cell membrane and a bacterial outer membrane, causing them to take up the counterstain (safranin or fuchsine) and appear red or pink.

Despite their thicker peptidoglycan layer, gram-positive bacteria are more receptive to certain cell wall targeting antibiotics than gram-negative bacteria, due to the absence of the outer membrane
, the following characteristics are present in gram-positive bacteria:
Cytoplasmic lipid membrane
Thick peptidoglycan layer
Teichoic acids and lipoids are present, forming lipoteichoic acids, which serve as chelating agents, and also for certain types of adherence.
Peptidoglycan chains are cross-linked to form rigid cell walls by a bacterial enzyme DD-transpeptidase.
A much smaller volume of periplasm than that in gram-negative bacteria.
Gram positive cells have two layers- inner cytoplasmic membrane and outer thick peptidoglycan
Whereas gram negative cells have three layers-inner cytoplasmic membrane, thin peptidoglycan layer and outer membrane with lipopolysaccharide
Gram positive have low lipid content while gram negative have high lipid content
Gram positive have no endotoxins while gram negative have endotoxin-lipid A
Gram positive have no porins while gram negative have porin channels
Gram positive are vulnerable to lysozyme and penicillin attack while gram negative are resistant to lysozyme and penicillin attack

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Difference between Gram positive bacteria and Gram negative bacteria | Gram +ve or gram -ve अंतर

Is video me hamne gram possitive bacteria or gram negative becteria me difference bataya hai.
मेरा नाम Dinesh kumar है।
1:BMLT in peoples paramedical college bhopal.
Microbiology, biochemistry.department experience Total 4 year.
3: Current job as a lab technician in govt hospital pathology and TB diagnosis department.

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Gram positive vs Gram Negative Bacteria | Microbiology | Medicos Scientia

Gram positive vs gram negative bacteria

Important concept for antibiotic

Gram Positive vs Gram Negative Bacteria

According to gram staining bacteria are classified into two major types gram positive and gram negative.
in this video you will learn what are the major differences between these two types on the basis of what characteristics.
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