Bacteria are broadly classified as gram-positive and gram-negative bacteria based on gram stain.
But both of the groups are Prokaryotic cells similar in many aspects. Check the similarities at the end after the table.
Differences between gram positive and gram negative bacteria
|Sl.No||Features||Gram +ve Bacteria||Gram -ve Bacteria|
|1||Gram Stain||The gram-positive bacteria will stain blue or purple color when observed under a microscope.||The gram-negative bacteria will stain pink or red color under a microscope.|
|2||Gram Stain Reaction||The bacteria will retain the crystal violet dye.||The gram-negative bacteria cannot retain crystal violet and so it accepts the safranin dye.|
|3||Cell wall layer||The cell wall is a single layer||The cell wall is triple-layered.|
|4||Cell wall layer components||Entirely made of one component, i.e., mucopeptide.||Each layer has (from outside to inside)|
|5||Cell wall Shape||The gram-positive bacteria contain flat and even cell walls.||The gram-negative bacteria|
contain wavy and uneven cell walls.
|6||Elasticity||The cell wall is very rigid and has minimal elasticity.||The cell wall is less rigid, so it has high elasticity.|
|7||Peptidoglycan in cell wall||The proportion of|
peptidoglycan present in the gram-positive bacteria is 80%.
|The proportion of the|
peptidoglycan present in the gram-negative bacteria is 2-12%.
|8||Cell wall Thickness||Varies between 15-20nm thickness. Some of the bacteria contain an 80nm thickness cell wall.||The thickness of the cell wall in gram gram-positive bacteria varies between 7.5-12nm.|
|The muramic acid content in the gram-positive bacteria is 16-20%.||The muramic acid content in the gram-negative bacteria is 2-5%.|
|10||Cell wall Resistance||The cell wall is resistant to the alkali and is insoluble in even 1% KOH solution.||It is sensitive to alkali and is soluble in 1% KOH solution.|
|11||Resistance to Physical|
|The gram-positive cell is highly resistant to physical disruptions due to the presence of a rich peptidoglycan layer||Gram-negative bacteria are less resistant to physical damage|
|12||S-layer (Surface layer in the cell wall)||In the cell wall, the S-layer is attached to the peptidoglycan layer.||Here the S-layer is attached to the|
|13||Teichoic acid||As seen in the diagram, Teichoic acid is present in the cell wall.||Teichoic acid is absent|
|The gram-positive bacteria do not have the periplasmic space.||The gram-negative bacteria have a periplasmic space. This differentiates the outer membrane and the plasma|
|15||Outer membrane||It is absent here as the peptidoglycan layer makes up the whole layer||It is present above the thin layer of peptidoglycan|
|16||Lipid Content||The lipid content is low and is in the range of 1-4%.||The lipid content is very high in the range of 11-22%.|
|17||Porin channels||The proteinaceous membrane channels called porins are absent|
in the cell wall.
|The proteinaceous membrane channels are distributed in the outer membrane.|
|18||Lipopolysaccharides||Lipopolysaccharides are absent in the layer of the plasma membrane.||Lipopolysaccharides are present in the layer|
of the outer membrane.
|19||Mesosomes||Mesosomes are prominent in the gram-negative.||Mesosomes are less|
prominent in the gram-negative.
|20||Endospores||During unfavorable conditions, the|
bacteria transform into endospores.
|Usually do not transform into endospores|
|21||Flagella components||The basal body of the flagella in gram-positive bacteria contains two rings.||The basal body of the flagella in gram-negative bacteria contains four rings.|
|22||Toxins||Most of them can produce exotoxins.||Most of them produce endotoxins.|
|23||Antibiotic resistance||They are less resistant to antibiotics||Moderately resistant to antibiotics|
|24||Antibiotic susceptibility||They show high sensitivity to penicillin and sulfonamides antibiotics.||They show low to moderate susceptibility to next-generation penicillins and cephalosporins like|
|But show low susceptibility to antibiotics like the aminoglycosides,|
chloramphenicol and tetracyclines.
|But show high susceptibility to|
and tetracycline antibiotics.
|25||Sodium azide resistance (a preservative)||Highly resistant to sodium azide solution||Less resistant to the|
sodium azide solution.
|The cell wall is highly susceptible to degradation by lysozyme enzymes.||The cell wall is less susceptible to the lysozyme enzyme.|
|27||Dry climate tolerance||Gram-positives have|
a high tolerance to
dryness as the mucopeptide layer prevents water loss from cells.
|Have less tolerance to dryness.|
|28||Magnetosomes||Absent in these bacteria||Some of them have|
|29||Pathogenicity||Very few of them are pathogenic to|
humans and animals.
|Most of them are pathogenic to|
humans and animals
|30||Examples||Staphylococcus, Bacillus subtitles,|
Leuconostoc, Clostridium-like species.
|Helicobacter pyroli, E. coli, Rhizobium, Vibrio, Acetobacter, etc.|
Similarities between them
- They both possess capsules.
- Both have the covalently closed circular DNA as the genetic material.
- They both contain extra-chromosomal genetic material (plasmids).
- Both undergo binary fission as a mode of asexual reproduction.
- Both groups included the flagellated (motile) and non-flagellated (non-motile) forms.