Fixation (histology)
Preserving biological tissues from decay for microscopic examination.
To prepare tissue for examination, fixation kills the sample and halts autolysis and putrefaction, keeping biological material as close to its natural state as possible.[1] Artifacts that hinder interpretation of cellular ultrastructure are introduced by fixation, and even the most careful procedure alters the sample.[2]
Quick Facts
- Common fixatives
- Formaldehyde
- glutaraldehyde
- methanol
- Artifact example
- Bacterial mesosome (later shown to be an artifact of chemical fixation)
Facts from the source article.
Key facts and history
Fixation of tissue is done for several reasons, including killing the tissue to prevent autolysis and putrefaction.[1] After the smear dries, the slide is passed through a Bunsen burner flame several times to heat-kill and adhere the organism.[3] Cross-linking, the most effective stabilization of structure, occurs when a compound that adds chemically to macromolecules can combine with parts of two different macromolecules.[1] In the 1970s, the bacterial mesosome was considered an organelle in gram-positive bacteria; later, techniques developed for electron microscopy showed it to be an artifact of chemical fixation.[2]
Single cell organisms, most commonly bacteria and archaea, are fixed using heat fixation.[3] Overall morphology is generally preserved by heat fixation, but internal structures are not.[3]
What the research sources say
The scienceprofonline.com account states that heat fixation kills the bacteria, firmly attaches the smear to the microscope slide, and allows the sample to more readily take up the stain.[4]
References
- Wikipedia, "Fixation (histology)" (CC BY-SA 4.0), which cites: "Histotechnology: A Self-Instructional Text", American Society for Clinical Pathology Press, 2009, p. 2 (we also read that source) en.wikipedia.org
- Wikipedia, "Fixation (histology)" (CC BY-SA 4.0), which cites: "Contribution of new cryomethods to a better knowledge of bacterial anatomy", Annales de l'Institut Pasteur. Microbiology, 1988, p. 33–44; "Antibacterial action of structurally diverse cationic peptides on gram-positive bacteria", Antimicrobial Agents and Chemotherapy, August 2000, p. 2086–2092 (original not read by us) en.wikipedia.org
- Wikipedia, "Fixation (histology)" (CC BY-SA 4.0), which cites: "How to Prepare & Heat Fix a Bacterial Smear for Staining", www.scienceprofonline.com (we also read that source) en.wikipedia.org
- "How to Prepare & Heat Fix a Bacterial Smear for Staining", www.scienceprofonline.com. facts only, no text reused. scienceprofonline.com
Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Fixation (histology) (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.
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