Differences between Gram Positive and Gram Negative Bacteria

S.N.CharacteristicsGram PositiveGram Negative
1Gram ReactionGram Positive Stain


Retain crystal violet dye and stain blue or purple

Gram Negative Stain


Can be decolorized to accept counterstain (safranin) and stain pink or red

2Cell WallCell Wall is 20-30 nm thick.Cell Wall is 8-12 nm thick.
3Cell WallThe wall is Smooth.The wall is wavy.
4Peptidoglycan LayerThick (multilayered)Thin (single-layered)
5Teichoic AcidsPresent in manyAbsent
6Periplasmic SpaceAbsentPresent
7Outer MembraneAbsentPresent
8PorinsAbsentOccurs in Outer Membrane
9Lipopolysaccharide (LPS) ContentVirtually NoneHigh
10Lipid and Lipoprotein ContentLow (acid-fast bacteria have lipids linked to peptidoglycan)High (because of presence of outer membrane)
11MesosomesQuite ProminentLess Prominent
12Flagellar Structure2 rings in basal body4 rings in basal body
13Toxin ProducedExotoxinsEndotoxins or Exotoxins
14Resistance to Physical DisruptionHighLow
15Cell Wall Disruption by LysozymeHighLow (requires pretreatment to destabilize outer membrane)
16Susceptibility to Penicillin and SulfonamideHighLow
17Susceptibility to Streptomycin, Chloramphenicol and TetracyclineLowHigh
18Inhibition by Basic DyesHighLow
19Susceptibility to Anionic DetergentsHighLow
20Resistance to Sodium AzideHighLow
21Resistance to DryingHighLow

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35 thoughts on “Differences between Gram Positive and Gram Negative Bacteria”

  1. Gram positive bacteria can retain the Cristal violet colour even after washed with acetone or alchol and appears a purple coloured when examined under the microscope after gram staing

  2. the difference is clear but in simple explanation gram staining is what makes bacteria to be gram positive or negative and this happens because gram positive bacteria have thick peptidoglycan which retains crystal violet staining dye as opposed to gram.

  3. What is the reason that inhibition by basic dyes, susceptibility to anionic detergents and resistance to sodium azide is low in gram negative while high in gram positive bacteria?
    Answer plz it’s assignment

  4. Thanks alot I’m a clinical medicine and surgery student under microbiology unit I had to study about gram positive and negative so you’ve made it easier for me God bless

  5. I Would like to know the fundamental characters that differentiates these two.All you have mentioned are the secondary one,i guess.The distinction seems not clearly made on why one bacteria is called gram positive and the other negative.I would appreciate any notes regarding this.
    Hoping for your reply.

    • In response to your question on why one is called grams positive and the order grams negative. The reason is the ability of one to turn purple or blue when dye is added to it cell due to the presence of high level of peptidoglycan where as the order has low peptidoglycan and when stained it turns pink most of the time

  6. In segment 13 i.e. Toxin production it is more accurate to write under gram negative bacteria exotoxins and/or endotoxins rather than exotoxins or endotoxins because endotoxins are produced by all gram negative bacteria as it ( the LPS) is an integral part of the outer membrane, so any species produce exotoxins will already produce both.

  7. If you are able to open the site in Chrome from your phone, you cannot see the entire page on the screen, but you can save the table to Drive in landscape as a PDF and it looks great.

  8. A good website…can i know the answers of these questions please?
    1:What are the basic requirements for a good germicide?
    2:Why is B.subtilis more resistant to phenol than e.coli?
    3:Do sensitive bacteria become resistant to antibiotics? if yes why?

  9. Thanks a lot
    if sources are in hand please send the characteristics of gram negative and positive bacteria on media’s (colony characterization, color etc)

  10. thank can i please know the source of this post? name of book, author and the page. thank you very much i used it for my homework and we are required to write the source.

    • gram positive have the ability to retain the color of the primary stain (crystal violet), while gram negative do not

  11. Anyone to give me the difference between the gram positive cell wall and gram negative cell wall,,, whenever i think i get less than three, please

    • Protozoan are mainly unicellular and microscopic. Fungi is majorly filamentous.
      Protozoan are parasitic , Fungi are parasitic and saprophytic

      amoebiasis, malaria , are some protozoan diseases

      major skin diseases aspergilloses, candidiasis, blstomycosis

  12. Please the topic is the diff between gram positive bacteria and gram negative bacteria but the distinction seem not to be clearly made. Pls help

    • The gram positive Retain crystal violet dye and stain blue or purple white the gram negative do not retain , and Can be decolorized to accept counterstain (safranin) and stain pink or red

    • Does one species of bacteria have both gram -ve and gram +ve bacteria e.g eschericia coli ?

  13. How does a a diderm or double cell walled bacteria like the Borrelia species fit in?
    Is there enough information to add a third column?

  14. Hlo sir im doing bsc biotech nd i want some guidance frm u fr msc studies .im interested in microbiology but im confused between biotech nd microbiology fr msc pls guide me nd sujust sm other gud fields olso fr masters thnku

  15. A very complete and useful tool for understanding. I consider that selected colors are confuse, because in a real Gram stain gramnegatives are pink and grampositives are violet, instead the colors showed in the figure.

    • yes you are very true…coz its very difficult todistinguished between this two gram bacteria on the basis of this grahm staning coz the colour seems same as pinkband violet..I think other innovative distinguishing colour should be prepared..

    • The colors of the illustration were poorly thought out, for sure, but I I always think
      POSITIVE (gram+) PURPLE (violet stain) PEPTIDOGLYCAN (thick)

      Because the G- stain varies from pink to red, I simply focus memorization by gram stain color for Positive Purple… in either/or items you only need to be obsessive about one OR the other…at least as one begins a journey into Microbial world.


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