Some Comparative Characteristics of Gram-Positive and Gram- Negative Bacteria

Gram- Positive

Gram reaction

Retain crystal violet dye and stain dark violet or purple

Gram- Negative

Gram reaction:

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

Gram- Positive

Peptidoglycan layer:

thick (multilayered)

Gram- Negative

Peptidoglycan layer:

Thin (single- layered)

Gram- Positive

Teichoic acids:

Present in many

Gram- Negative

Teichoic acids:

Absent

Gram- Positive

Periplasmic space:

Absent

Gram- Negative

Perplasmic space:

Present

Gram- Positive

Outer membrane:

Absent

Gram- Negative

Outer membrane :

Present

Gram- positive

Lipopolysaccharide (LPS) content:

Virtually none

Gram- negative

Lipopolysaccharide (LPS) content :

High

Gram- Negative

Lipid and lipoprotein content:

Low (acid-fast bacteria have lipids linked to peptidoglycan)

Gram- Negative

Lipid and lipoprotein content :

High (due to presence of outer membrane)

Gram- Positive

Flagellar structure:

2 rings in basal body

Gram negative

Flagellar structure:

4 rings in basal body

Gram- Positive

Toxins produced :

Primarily exotoxins

Gram- Negative

Toxins produced :

Primarily endotoxins

Gram- Positive

Resistance to physical disruption: High

Susceptibility to penicillin and sulfonamide: High

Gram- Negative

Resistance to physical disruption :

Low

Gram - Positive

Cell wall disruption by lysozyme:

High

Gram- Negative

Cell wall disruption by lysozyme :

Low (requires pretreatment to destabilize outer membrane)

Gram- Positive

Inhibition by basic dyes: High

Susceptibility to anionic detergents: High

Resistance to sodium azide: High:

Resistance to drying p: High

Gram- Negative

Inhibition by basic dyes: Low

Susceptibility to anionic detergents: Low

Resistance to sodium azide: Low

Resistance to drying p: Low