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Gram negative

2017-10-20T14:47:24Z

170660868:

Bacteria are categorised into two main subgroups 'Gram negative' and '[[Gram positive]]' bacteria (with the exception of [[Mycobacterium Tuberculosis|''Mycobacterium tuberculosis'']] which falls into neither of the two groups.) The Gram method of classification is dependent upon cell wall structure. In this article I am going to focus on the 'Gram negative' wall structure.

A Gram negative bacteria has a base lipid bi-layer similar to an [[Eukaryotic|eukaryotic]] plasma membrane, surrounded by the [[Periplasmic space|periplasmic space]]. A thin [[Peptidoglycan|peptidoglycan]] layer, much thinner in comparison to that of the gram positive bacteria then arises seperating the two periplasmic compartments. Peptidoglycan is a polymer made up of two repeating units of [[N-acetylmumaric acid|N-acetylmumaric acid and]] [[N-acetylglucosamine|N-acetylglucosamine which]] form linear chains due to cross linkages formed by the tetrapeptide side chains of the monomers. The outermost external barrier of a gram negative bacteria is a lipid like bi-layer, but this is highly disimilar from that of an eukaryotic plasma membrane. The inner leaflet of this outer membrane is studded with [[Lipoproteins|lipoproteins]] which associate to the [[Cytoskeleton|cytoskeleton]] and peptidoglycan layer. The outer leaflet is made up of [[LPS lipidpolysaccharide|LPS lipidpolysaccharide]]; composed of [[Lipid A|Lipid A]] a functional [[Endotoxin|endotoxin]] when released and an [[O polysacharide tail|O polysacharide tail]].

Due to the lipid characteristics of the outermost membrane of the cell wall the gram negative bacteria are stained pink when [[Gram staining|gram stained]].

Gram-negative refers to a classification of bacteria based upon their cell wall structure. Gram-negative bacteria appear red as a result of Gram testing, whereas Gram-positive stain purple.

The structure of the Gram-negative bacterial cell wall is what distinguishes it from [[Gram positive|Gram-positive]] bacteria. Gram-negative bacteria contain a much thinner layer of [[Peptidoglycan|Peptidoglycan]] in comparison to a Gram-positive bacterial cell wall. The Gram-negative cell wall consists of a unique outer membrane, containing [[Lipopolysaccharides|lipopolysaccharides]], murein [[Lipoproteins|lipoproteins]] and porin channels. There is also a periplasmic space between the peptidoglycan cell wall, and the cell membrane.

Gram-negative bacteria exhibit stronger resistance to antibiotics such as [[Lysozyme|Lysozyme]] and pennicillin G, as well as greater resistance to dyes and detergents. The lipopolysaccharide consists of a core polysaccharide, Lipid A and O-antigen. This lipolysaccharide layer is important in excluding large hydrophobic susbstances from interacting with the cell. Lipid A attaches to the outer membrane ensuring that the lipopolysaccharide remains attached to the cell .<br><br>

Gram negative

2017-10-20T14:46:20Z

170660868:

Bacteria are categorised into two main subgroups 'Gram negative' and '[[Gram positive]]' bacteria (with the exception of [[Mycobacterium Tuberculosis|''Mycobacterium tuberculosis'']] which falls into neither of the two groups.) The Gram method of classification is dependent upon cell wall structure. In this article I am going to focus on the 'Gram negative' wall structure.

A Gram negative bacteria has a base lipid bi-layer similar to an [[Eukaryotic|eukaryotic]] plasma membrane, surrounded by the [[Periplasmic space|periplasmic space]]. A thin [[Peptidoglycan|peptidoglycan]] layer, much thinner in comparison to that of the gram positive bacteria then arises seperating the two periplasmic compartments. Peptidoglycan is a polymer made up of two repeating units of [[N-acetylmumaric acid|N-acetylmumaric acid and]] [[N-acetylglucosamine|N-acetylglucosamine which]] form linear chains due to cross linkages formed by the tetrapeptide side chains of the monomers. The outermost external barrier of a gram negative bacteria is a lipid like bi-layer, but this is highly disimilar from that of an eukaryotic plasma membrane. The inner leaflet of this outer membrane is studded with [[Lipoproteins|lipoproteins]] which associate to the [[Cytoskeleton|cytoskeleton]] and peptidoglycan layer. The outer leaflet is made up of [[LPS lipidpolysaccharide|LPS lipidpolysaccharide]]; composed of [[Lipid A|Lipid A]] a functional [[Endotoxin|endotoxin]] when released and an [[O polysacharide tail|O polysacharide tail]].

Due to the lipid characteristics of the outermost membrane of the cell wall the gram negative bacteria are stained pink when [[Gram staining|gram stained]].

Gram-negative refers to a classification of bacteria based upon their cell wall structure. Gram-negative bacteria appear red as a result of Gram testing, whereas Gram-positive stain purple.

The structure of the Gram-negative bacterial cell wall is what distinguishes it from [[Gram positive|Gram-positive]] bacteria. Gram-negative bacteria contain a much thinner layer of [[Peptidoglycan|Peptidoglycan]] in comparison to a Gram-positive bacterial cell wall. The Gram-negative cell wall consists of a unique outer membrane, containing [[Lipopolysaccharides|lipopolysaccharides]], murein [[Lipoproteins|lipoproteins]] and porin channels. There is also a periplasmic space between the peptidoglycan cell wall, and the cell membrane.

Gram-negative bacteria exhibit stronger resistance to Antibiotics such as [[Lysozyme|Lysozyme]] and pennicillin G, as well as greater resistance to dyes and detergents. The lipopolysaccharide consists of a core polysaccharide, Lipid A and O-antigen. This lipolysaccharide layer is important in excluding large hydrophobic susbstances from interacting with the cell. Lipid A attaches to the outer membrane ensuring that the lipopolysaccharide remains attached to the cell .<br><br>