Microbiology: Difference Between Gram Positive Bacteria VS Gram Negative Bacteria

Microbiology: Difference Between Gram Positive Bacteria VS Gram Negative Bacteria

 Gram staining  is a special technique which is used to stain bacteria. This technique was developed by Christian Gram in 1884. The stain  stain used in Gram staining is called Gram stain. Chemically Gram stain is a weakly alkaline solution of crystal violet or gentian violet.

On the basis of cell wall structure and its stain ability wit Gram stain, bacteria are grouped into two categories. They are Gram positive bacteria and Gram negative bacteria.

The bacteria which retain the color of the stain are called Gram positive bacteria.

Examples of Gram positive bacteria:

♦ Bacillus

♦ Nocardia

♦ Cornyebacterium

♦ Gardnerella

♦ Mycobacterium

♦ Mycoplasma

♦ Staphylococcus

♦ Listria

♦ Streptomyces

♦ Streptococcus

♦ Clostridium

♦ Propionibacterium

♦ Actinomyces

♦ Enterococcus

♦ Lactobacillus

The bacteria which lose the color of the stain are called Gram negative bacteria.

Examples of Gram negative bacteria:

♦ Escherichia coli (E.coli)

♦ Cyano bacteria

♦ Hemophilus

♦ Enterobacter

♦ Chlamydia

♦ Vibrio

♦ Pseudomona

♦ Salmonella

♦ Klebsiella

♦ Acetobacter

♦ Helicobcater

♦ Thiobacter

♦ Borrelia

♦ Burkholderia

♦ Serratia

♦ Treponema

♦ Neisseria

Gram Positive Bacteria

The bacteria  remain coloured with Gram staining even after washing with alcohol or acetone.

Outer membrane is absent.

Cell wall is 20-30 nm thick.

The wall is smooth

The wall contains 70-80% murein.

The lipid content in the wall is very low.

Cell wall contains teichoic acids.

Basal body of the flagellum contains  two rings.

Mesosomes are quite prominent.

A few pathogenic bacteria belong to Gram positive group.

Gram Negative Bacteria

The bacteria do not retain the stain when washed with alcohol or acetone.

Outer membrane is present.

Cell wall is 8-12 nm thick.

The wall is wavy and comes in contact with plasma membrane only at a few loci.

The wall contains 10-20% murein.

The lipid content in the wall is 20-30%.

Porins or hydrophilic channels occur in outer membrane.

Teichoic acids are absent.
Basal body of the flagellum has four rings.
Mesosomes are less prominent.

Most of the pathogenic bacteria belong to Gram negative group.