What is a gram stain?
Quick Answer
A gram stain is a laboratory test that classifies bacteria as Gram-positive or Gram-negative based on their cell wall structure. It remains one of microbiology’s most basic diagnostic methods.
The Full Story
The Gram stain, developed by Hans Christian Gram in 1884, uses dyes to distinguish bacteria with different cell wall structures. Gram-positive bacteria retain the purple dye because of their thick peptidoglycan layer, while Gram-negative bacteria do not and counterstain pink or red. This simple test helps narrow down a possible bacterial identity quickly in clinical and research labs. It is still widely used because it provides fast and useful information about bacterial structure.
Key Facts
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