Gram negative bacteria are the genus of bacteria family and a member of the phylum Firmicutes. They are the group of aerobic bacteria which does not retain the crystal violet dye during the procedure of Gram staining and appear pink in colour when examined under the microscope.
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There are several gram negative bacteria with medical significance. The most important of these are members of the family Enterobacteriaceae. Further genera of Gram negative bacteria include Vibrio, Campylobacter, Pseudomonas, and other bacteria which are normally found in the gastrointestinal tract.
Also Read: Gram Positive and Gram negative Bacteria
General Characteristics of Gram Negative Bacteria
The gram negative bacteria have the following characteristics:
- The cell wall is thin without an outer layer.
- A high percentage of lipids can be found.
- It contains all types of amino acids.
- The muramic acid content is less.
- It is sensitive to streptomycin.
- It is devoid of magnesium ribonucleate and teichoic acid.
- It contains lipopolysaccharides, sialic acid, and flagella.
Cell Structure of Gram Negative Bacteria
- The cell wall of Gram negative bacteria is thin and is composed of peptidoglycan.
- The cell envelope has 3 layers including, a unique outer membrane, a thin peptidoglycan layer, and the cytoplasmic membrane.
- An outer membrane of the cell wall is a bilayer structure consisting of phospholipids molecules, lipopolysaccharides (LPS), lipoproteins and surface proteins.
- Endotoxin is toxins released by the cell during infections and function as receptors and blocking immune response.
- The porin proteins are present in the upper layer of a cell which functions by regulating the entry and exit of the molecules within the cell.
Diseases caused by Gram Negative Bacteria
The diseases caused by gram negative bacteria are diarrhoea, inflammatory disease of the large intestine, infantile diarrhoea, kidney damage, typhoid fever, bubonic plague, cholera etc.
Also Read: Gram Positive Bacteria
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