It consists of an outer membrane over the peptidoglycan layer, unlike gram-positive bacteria. Gram-negative bacteria possess a continuous or smooth outer membrane, as it consists of lipopolysaccharide and porins in its structure. The absence of an outer membrane, porins and lipopolysaccharide in its cell structure is one of the distinguishing features. On the peptidoglycan layer of some bacteria, a negatively charged teichoic acid is found. The cell wall is thick due to a high peptidoglycan content, which is usually multilayered and having dense cross-linkages. Peptidoglycan constitutes about 70-80% of the cell weight, and lipid content is about 1-4% in the cell wall of the gram-positive bacteria. The cell wall of gram-positive bacteria is made of sacculus that are the continuous cells, which makes the surface of gram-positive bacteria more even and smooth. not retain the colour of primary stain and take the colour of counterstain (Safranin). Gram-negative bacteria: These are the type of bacteria, which appear Pink in colour by giving a negative reaction on gram staining, i.e. retain the colour of primary stain (Crystal violet). Gram-positive bacteria: These are the type of bacteria, which appear Violet in colour by giving a positive reaction on gram staining, i.e. Susceptibility to streptomycin, chloramphenicol and tetracyclineīacillus, Streptococcus, Clostridium, Corynebacterium etc.Įnterobacter, Acetobacter, Bortadella etc. Susceptibility to penicillin and sulphonamide Resistance to cell wall disruption by lysozyme High lipid content (20-30%) and low peptidoglycan content (10-20%) Low lipid content and high peptidoglycan content (70-80%) Gram-negative bacteria lose the colour of crystal violet and appear pink in colour after counterstaining with safranin due to its thin peptidoglycan layer.Ĭontent: Gram-Positive Vs Gram-Negative Bacteria ![]() Staining or colour difference: Gram-positive bacteria retain the colour of crystal violet (primary stain) and appear violet in colour due to its thick peptidoglycan cross-linkages. The outer membrane is made of lipopolysaccharide and porins, and they have more periplasmic space. Gram-negative bacteria contain low peptidoglycan content (10-20%) and high lipid content (20-30%).
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