Gram Negative Bacteria & Gram Positive Bacteria

The “gram-positive” and “gram negative” are terms used by microbiologists to classify bacteria. The classification is based on the bacterium’s chemical and physical cell wall properties. For proper determination as to weather a bacteria is gram-positive or gram-negative, microbiologist usually performs a special type of staining technique referred to as Gram Stain. The name gram stain comes from the name of the person who discovered it, Han Christian Gram (1884). The staining method uses crystal violet dye which is retained by the peptidoglycan cell wall of both gram negative and gram positive bacteria. This stain will either stain the cells purple (for positive) or pink (for negative).

What You Need To know About Gram Negative Bacteria (Major Characteristics)

• These are bacteria that are not able to retain the crystal violet color and show negative result to gram stain test.
• With exception of Neisseria, the rest are usually non-spore forming rods.
• The thickness of the cell wall is between 8 nm and 12 nm.
• More elastic and less rigid. The elasticity of the cell wall is due to the less amount of peptidoglycan, which is between 2-12%.
• The cell wall is sensitive to alkali.
• The cell wall is less sensitive to degradation by action of the lysozyme.
• Most pathogenic bacteria belong to gram negative group.
• There is several variety of amino acid in the cell wall of gram negative.
• Usually not found to produce endospores.
• Proteinaceous membrane channel referred to as porins are present.
• Lipid content is high. It is usually between 11-14%.
• The ration of RNA to DNA is 1:1

What You Need To Know About Gram Positive Bacteria (Major Characteristics)

• These are bacteria that give positive result to the gram stain test and take up the crystal violet stain.
• With exception of Lactobacillus and Corynebacterium, the rest are usually spore forming rods.
• The thickness of the cell wall can be up to 15-30 nm or sometimes can be 80 nm.
• The cell wall shows some resistance to alkali.
• Less elastic and more rigid. The rigidity of the cell wall is due to the high amount of peptodoglycan, which is between 70-80%.
• Cell wall contains muramic acid, which is between 16-20% of the total dry weight.
• There is few variety of amino acid in the cell wall.
• Cell wall contains muramic acid, which is between 16-20% of the total dry weight.
• The cell wall is very much susceptible to degradation by the action of the lysonzyme.
• Some produce endospores during unfavorable conditions.
• Few pathogenic bacteria belong to gram positive group.
• The flagellar structure has two rings in the basal body.
• Lipid content is low. It is usually between 1-4%.
• The ratio of RNA to DNA is 8:1

Also Read: Difference Between Staphylococcus And Streptococcus Bacteria

Difference Between Gram Positive And Gram Negative Bacteria In Tabular Form

Also Read: Difference Between Bacteria And Virus

What Are Some of the similarities Between Gram Positive Bacteria And Gram Negative Bacteria?

• Both gram positive and gram negative bacteria contain extra-chromosomal genetic materials (Plasmids).
• They both have a surface layer referred to as an S-layer.
• Both are bacterial cells and contain many flagellated and non-flagellated species.
• Both gram negative and gram positive bacteria have covalently closed circular DNA as the genetic material.
• Both gram positive and gram negative bacteria undergo binary fission as a mode of asexual reproduction.
• Gram negative and gram positive bacteria, both lack membrane bound organelles.
• Both are prokaryotic in nature.
• In both groups, cell wall is made up of peptidoglycan.
• Gram positive and gram negative bacteria undergo genetic recombination through transduction, transformation and conjugation.
• In both groups, cytoplasm is surrounded by lipid bilayer with many membrane spanning proteins.