basic difference between Gram +ve & Gram -ve bacteria, gram +ve and gram -ve bacteria, classes of bacteria

2. 1. Gram Staining
 Gr +ve:- Retain crystal violet dye and stain blue or purple on Gram’s
staining.
 Gr -ve:- Accept safranin after decolorization and stain pink or red on
Gram’s staining.
2. Cell wall Thickness
 Gr +ve:- Thick (20-80 nm)
 Gr -ve:- Thin (8-10 nm)
3. Peptidoglycan layer
 Gr +ve:- Thick (Multilayered)
 Gr -ve:- Thin (single layered)

3. 4. Rigidity & Elasticity
 Gr +ve:- Rigid & less elastic
 Gr -ve:- Less rigid & more elastic
5. Outer membrane
 Gr +ve:- Absent
 Gr -ve:- Present
6. Variety of amino acid in cell wall
 Gr +ve:- Few
 Gr -ve:- Several

4. 7. Aromatic & Sulfur containing amino acid in
cell wall
 Gr +ve:- Absent
 Gr -ve:- Present
8. Periplasmic space
 Gr +ve:- Absent
 Gr -ve:- Present
9. Teichoic acid
 Gr +ve:- Mostly present
 Gr -ve:- Absent

5. 10. Porins
 Gr +ve:- Absent
 Gr -ve:- Present
11. Lipopolysaccharides content
 Gr +ve:- Virtually none
 Gr -ve:- High
12. Lipid & Lipoprotein content
 Gr +ve:- Low (acid fast bacteria have lipid linked to peptidoglycans)
 Gr -ve:- High (because presence of outer membrane)

6. 13. Ratio of DNA & RNA
 Gr +ve:- 8:1
 Gr -ve:- Almost 1
14. Mesosomes
 Gr +ve:- Quite prominent
 Gr -ve:- Less prominent
15. Flagellar structure
 Gr +ve:- 2 rings in basal body
 Gr -ve:- 4 rings in basal body

7. 16. Magnetosomes
 Gr +ve:- Usually absent
 Gr -ve:- Sometimes present
17. Morphology
 Gr +ve:- Usually cocci or spore forming rods (exception: Lactobacillus &
cornebacterium)
 Gr -ve:- Usually non-spore forming rods (exception: Neisseria)
18. Endospore formation
 Gr +ve:- Some produce endospore during unfavorable conditions
 Gr -ve:- usually not found to produce endospores

8. 19. Toxin produced
 Gr +ve:- Exotoxins
 Gr -ve:- Endotoxins or Exotoxins
20. Pathogens
 Gr +ve:- Few pathogenic bacteria belongs to Gr +ve group
 Gr -ve:- Most pathogens are Gr –ve
21. Nutritional requirements
 Gr +ve:- Relatively complex
 Gr -ve:- Relatively simple

9. 22. Resistance to physical disruption
 Gr +ve:- High
 Gr -ve:- Low
23. Cell wall disruption by lysozyme
 Gr +ve:- High
 Gr -ve:- Low ( require pretreatment to destabilize outer
membrane)
24. Susceptibility to penicillin & sulfonamide
 Gr +ve:- High
 Gr -ve:- Low

10. 25. Susceptibility to streptomycin,
chloramphenicol & tetracycline
 Gr +ve:- Low
 Gr -ve:- High
26. Inhibition by basic dyes
 Gr +ve:- High
 Gr -ve:- Low
27. Susceptibility to anionic detergents
 Gr +ve:- High
 Gr -ve:- Low

11. 28. Resistance to sodium azide
29. Resistance to drying
 Gr +ve:- High
 Gr -ve:- Low
30. Rendering
 Gr +ve:- They can rendered Gr-ve by increasing acidity
 Gr -ve:- They can rendered Gr +ve by increasing alkalinity
 Gr +ve:- High
 Gr -ve:- Low

12. 31. Examples
 Gr +ve:-
 Staphylococcus
 Streptococcus
 Bacillus
 Clostridium
 Enterococcus
 Gr -ve:-
 Salmonella
 Escherichia
 Klebsiella
 Proteus
 Helicobacter
 Pseudomonas