Differences Between Gram Positive and Gram Negative Bacteria

Gram Staining technique is the most important and widely used microbiological differential staining technique. It categorizes bacteria according to their Gram character (Gram positive or Gram negative).
Along with their staining characteristics, Gram Positive and Gram Negative bacteria differ from each other in various aspects which are listed below :


S.N.CharacteristicsGram PositiveGram Negative
1.Gram ReactionRetain crystal violet dye and stain blue or purple.


Accept safranin and stain pink or red


2.Cell Wall StructureStructure of Gram Positive cell wall :
Structure of Gram Negative cell wall :
3.Cell Wall ThicknessThick (20-80 nm)Thin (8-10 nm)
4.Chemical Composition of Cell WallPeptidoglycan, Teichoic acid Lipotechoic acidLipopolysaccharide, Lipoproteins and Peptidoglycans
5.Peptidoglycan LayerThick (Multilayered)Thin (Single layered)
6.Teichoic Acid in Cell WallPresentAbsent
7.Lipopolysaccharide Layer (Outer Layer)AbsentPresent
8.Lipid ContentAbsent or lower content of lipids than Gram Negative bacteriaContains higher content of lipids than Gram positive bacteria (due to presence of outer membrane)
9.Porin ProteinsAbsentPresent
10.Flagellar Structure2 rings in basal body4 rings in basal body
11.Periplasmic SpaceAbsentPresent
12.MesosomeMore prominentLess prominent
13.Ratio of RNA:DNA8:1Almost 1
14.Toxins ProducedPrimarily ExotoxinsEndotoxins and Exotoxins (Primarily Endotoxins)
15.Resistance to Physical DisruptionHighLow
16.Cell Wall Disruption by LysozymeHigh.
After digestion of peptidoglycan layer, Gram +ve bacteria become Protoplast.
After digestion of peptidoglycan layer, Gram -ve bacteria become Spheroplast.
17.Susceptibility to Penicilin and SulphonamideHighLow
18.Susceptibility to Streptomycin, Chloramphenicol and TetracyclineLowHigh
19.Inhibition by Basic DyesHighLow
20.Susceptibility to ionic detergentsHighLow
21.Resistance to Sodium AzideHighLow
22.Resistance to DryingHighLow
23.Isoelectric Range pH2.5-4.04.5-5.5
24.Nutritional RequirementsRelatively ComplexRelatively Simple
25.RenderingThey can rendered Gram -ve by increasing acidityThey can rendered Gram +ve by increasing alkalinity
26.MorphologyUsually cocci or spore forming rods (exception : Lactobacillus and Corynebacterium)Usually non-spore forming rods (Exception : Neisseria)
  • Staphylococcus
  • Streptococcus
  • Bacillus
  • Clostridium
  • Nocardia
  • Propionibacterium
  • Enterococcus
  • Corynebacterium
  • Listeria
  • Lactobacillus
  • Gardnerella
  • Escherichia
  • Salmonella
  • Klebsiella
  • Proteus
  • Helicobacter
  • Hemophilus
  • Vibrio
  • Shigella
  • Neisseria
  • Enterobacter
  • Pseudomonas

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4 Responses to Differences Between Gram Positive and Gram Negative Bacteria

  1. akshay June 12, 2016 at 8:13 am #

    figure of gram negative and positive bacteria is given incorrect.please have a look…

  2. asad October 11, 2016 at 9:17 pm #

    Figure gram positive and negative walls is just confusing please take a look.

  3. monkeybaby February 24, 2017 at 7:29 pm #

    The pics for gram neg and gram pos cell walls need to be swapped! Just thought I’d let you know. 😉

  4. Nadjo Deen March 21, 2017 at 10:00 pm #

    where can I get ur pdf filed to download ?

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