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AAT Bioquest

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

Posted February 25, 2020


Answer

Bacteria are classified into gram positive and gram negative, the categories that are based on the composition and reaction of their cell walls to Gram stain test, developed by Hans Christian Gram. The differences between gram positive and gram negative bacteria are outlined in Table 1.


Table 1. The differences between gram positive and gram negative bacteria.

FeaturesGram-negativeGram-positive
Gram reactionStain red or pink and don’t retain the stain when washed with absolute alcohol and acetoneStain dark violet or purple and retain the stain when washed with absolute alcohol and water
Peptidoglycan layerThinThick
Outer membranePresentAbsent
Toxins producedEndotoxinsExotoxins
Antibiotic resistanceMore resistantLess resistant
Cell wallThe cell wall is 70-120 Å (ångström) thick; two layered.The cell wall is 100-120 Å thick; single layered.
Additional resources

MycoLight Rapid Fluorescence Bacterial Gram Stain Kit

MycoLight™ Rapid Fluorescence Gram-Positive Bacteria Staining Kit