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. | Characteristics | Gram Positive | Gram Negative |
|---|---|---|---|
| 1. | Gram Reaction | Retain crystal violet dye and stain blue or purple.
| Accept safranin and stain pink or red
|
| 2. | Cell Wall Structure | Structure of Gram Positive cell wall : | Structure of Gram Negative cell wall : |
| 3. | Cell Wall Thickness | Thick (20-80 nm) | Thin (8-10 nm) |
| 4. | Chemical Composition of Cell Wall | Peptidoglycan, Teichoic acid Lipotechoic acid | Lipopolysaccharide, Lipoproteins and Peptidoglycans |
| 5. | Peptidoglycan Layer | Thick (Multilayered) | Thin (Single layered) |
| 6. | Teichoic Acid in Cell Wall | Present | Absent |
| 7. | Lipopolysaccharide Layer (Outer Layer) | Absent | Present |
| 8. | Lipid Content | Absent or lower content of lipids than Gram Negative bacteria | Contains higher content of lipids than Gram positive bacteria (due to presence of outer membrane) |
| 9. | Porin Proteins | Absent | Present |
| 10. | Flagellar Structure | 2 rings in basal body | 4 rings in basal body |
| 11. | Periplasmic Space | Absent | Present |
| 12. | Mesosome | More prominent | Less prominent |
| 13. | Ratio of RNA:DNA | 8:1 | Almost 1 |
| 14. | Toxins Produced | Primarily Exotoxins | Endotoxins and Exotoxins (Primarily Endotoxins) |
| 15. | Resistance to Physical Disruption | High | Low |
| 16. | Cell Wall Disruption by Lysozyme | High. After digestion of peptidoglycan layer, Gram +ve bacteria become Protoplast. | Low. After digestion of peptidoglycan layer, Gram -ve bacteria become Spheroplast. |
| 17. | Susceptibility to Penicilin and Sulphonamide | High | Low |
| 18. | Susceptibility to Streptomycin, Chloramphenicol and Tetracycline | Low | High |
| 19. | Inhibition by Basic Dyes | High | Low |
| 20. | Susceptibility to ionic detergents | High | Low |
| 21. | Resistance to Sodium Azide | High | Low |
| 22. | Resistance to Drying | High | Low |
| 23. | Isoelectric Range pH | 2.5-4.0 | 4.5-5.5 |
| 24. | Nutritional Requirements | Relatively Complex | Relatively Simple |
| 25. | Rendering | They can rendered Gram -ve by increasing acidity | They can rendered Gram +ve by increasing alkalinity |
| 26. | Morphology | Usually cocci or spore forming rods (exception : Lactobacillus and Corynebacterium) | Usually non-spore forming rods (Exception : Neisseria) |
| 27. | Examples |
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figure of gram negative and positive bacteria is given incorrect.please have a look…
Figure gram positive and negative walls is just confusing please take a look.
The pics for gram neg and gram pos cell walls need to be swapped! Just thought I’d let you know. 😉
where can I get ur pdf filed to download ?