AAT Bioquest

What are the differences between gram stain and culture?

Posted September 17, 2022


Gram stain and culture are two completely different techniques with several significant differences between them. 

Basis of differentiationGram stainCulture
DefinitionIs a differential staining technique used to identify the presence of bacteria and differentiate between types of bacteriaIs a method of preparing and maintaining microorganism in a laboratory
PurposeIs used to differentiate bacteria into two main groups – gram positive bacteria and gram negative bacteriaIs used to multiply microorganisms for various purposes such as testing, chemical purification, and storage among others
Components used in the procedureUses two stains – crystal violet and safranin, mordant such as iodine solution, decolorizer such as ethanol, and waterUses an array of nutrient-rich culture media that may be solid, semi-solid or liquid
Basis of techniqueBased on the differences in the thickness of the peptidoglycan layer of the cell wallBased on the ability of microorganisms to grow and multiply inside a favorable culture media
OutcomeGram positive bacteria appear purple in color and gram negative bacteria appear pink in color Colonies of the microorganisms are visible on solid and semi-solid media. In liquid media, microorganisms are visible in suspended form 


Additional resources

Gram Staining

MycoLight™ Green JJ98

MycoLight™ Rapid Fluorescence Gram-Positive Bacteria Staining Kit