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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.
| Features | Gram-negative | Gram-positive |
| Gram reaction | Stain red or pink and don’t retain the stain when washed with absolute alcohol and acetone | Stain dark violet or purple and retain the stain when washed with absolute alcohol and water |
| Peptidoglycan layer | Thin | Thick |
| Outer membrane | Present | Absent |
| Toxins produced | Endotoxins | Exotoxins |
| Antibiotic resistance | More resistant | Less resistant |
| Cell wall | The 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