Question

What is the difference between gram positive bacteria and gram negative bacteria?

Answer 1

Danish scientist Hans Christian Gram devised a method to differentiate two types of bacteria based on the structural differences in their cell walls. In his test, bacteria that retain the crystal violet dye do so because of a thick layer of peptidoglycan and are called Gram-positive bacteria. In contrast, Gram-negative bacteria do not retain the violet dye and are colored red or pink. Compared with Gram-positive bacteria, Gram-negative bacteria are more resistant against antibodies because of their impenetrable cell wall. These bacteria have a wide variety of applications ranging from medical treatment to industrial use and Swiss cheese production.

Comparison chart

Gram-negative Bacteria versus Gram-positive Bacteria comparison chartGram-negative BacteriaGram-positive BacteriaGram reactionCan be decolourized to accept counter stain (Safranin or Fuchsine); stain red or pink, they don't retain the Gram stain when washed with absolute alcohol and acetone.Retain crystal violet dye and stain dark violet or purple, they remain coloured blue or purple with gram stain when washed with absolute alcohol and water.Peptidoglycan layerThin (single-layered)Thick (multilayered)Teichoic acidsAbsentPresent in manyPeriplasmic spacepresentAbsentOuter membranePresentAbsentLipopolysaccharide (LPS) contentHighVirtually noneLipid and lipoprotein contentHigh (due to presence of outer membrane)Low (acid-fast bacteria have lipids linked to peptidoglycan)Flagellar structure4 rings in basal body2 rings in basal bodyToxins producedPrimarily EndotoxinsPrimarily

Answer 2

The following listed below points describes the differences between gram +ve and gram -ve bacteria -

1. The bacteria which are gram +ve type shows the stain even after washing. Whereas the gram -ve bacteria does not possess the stain.

2. Gram +ve type of bacteria has wall which is smooth while the -ve gram type bacteria has wavy type of cell wall.