National Cancer Institute (source definition)
Gram Staining Method
This is a method (named after the Danish bacteriologist, Hans Christian Gram) for staining and identifying bacteria. It is based on the differential retention of a crystal violet-iodine complex within the cell membrane. Gram-positive organisms will appear blue-black or purple while Gram-negative organisms will appear red.
Review and references
Automated source check (NCI definition)
2026-10-18
2026-10-19
professional use
References
- NCI Thesaurus 26.09d — Gram Staining Method (C23014)
- Source: National Cancer Institute, NCI Thesaurus 26.09d, C23014. NCI definition, reproduced without modification under CC BY 4.0.
- Improvement of gram staining effect by ethanol pretreatment and quantization of staining image by unsupervised machine learning. — Arch Microbiol, 2024-06-21 (PMID 38904719; literature)
What it is
This is a method (named after the Danish bacteriologist, Hans Christian Gram) for staining and identifying bacteria. It is based on the differential retention of a crystal violet-iodine complex within the cell membrane. Gram-positive organisms will appear blue-black or purple while Gram-negative organisms will appear red.
Source: National Cancer Institute, NCI Thesaurus 26.09d, C23014. NCI definition, reproduced without modification under CC BY 4.0.
Source identity and definition checked automatically on 2026-10-18. No individual clinical interpretation or human reviewer is asserted.
Compliance note
Reference intervals and interpretation depend on the laboratory, specimen, method and clinical context. This source definition is educational information; it does not establish a diagnosis, product approval or suitability for an individual.