The Schaeffer–Fulton stain is a technique designed to isolate
endospore
An endospore is a dormant, tough, and non-reproductive structure produced by some bacteria in the phylum Bacillota. The name "endospore" is suggestive of a spore or seed-like form (''endo'' means 'within'), but it is not a true spore (i.e., not ...
s by staining any present endospores green, and any other bacterial bodies red.
[Definition:Schaeffer-Fulton Stain](_blank)
/ref> The primary stain is malachite green, and the counterstain is safranin
Safranin (Safranin O or basic red 2) is a biological stain used in histology and cytology. Safranin is used as a counterstain in some staining protocols, colouring cell nuclei red. This is the classic counterstain in both Gram stains and endo ...
, which dyes any other bacterial bodies red.
Endospores cannot be stained by normal staining procedures because their walls are practically impermeable to all chemicals. The Schaeffer- Fulton endospore stain uses heat to drive the primary stain(malachite green) into the endospore. After cooling, the slide is decolorized with water and counterstained with safranin.
Procedure
Using an aseptic technique, bacteria are placed on a slide and heat fixed. The slide is then suspended over a water bath with some sort of porus paper over it, so that the slide is steamed
Steaming is a method of cooking using steam. This is often done with a food steamer, a kitchen appliance made specifically to cook food with steam, but food can also be steamed in a wok. In the American Southwest, steam pits used for cooking ha ...
. Malachite green is applied to the slide, which can penetrate the tough walls of the endospores, staining them green. After five minutes, the slide is removed from the steam, and the paper towel is removed. After cooling, the slide is rinsed with water for thirty seconds. The slide is then stained with diluted safranin for two minutes, which stains most other microorganic bodies red or pink. The slide is then rinsed again, and blotted dry with bibulous paper.[Harley and Prescott: ''Laboratory Exercises in Microbiology'', page 58. McGraw Hill, 2002.]
After drying, the slide can then be viewed under a light microscope
The optical microscope, also referred to as a light microscope, is a type of microscope that commonly uses visible spectrum, visible light and a system of lens (optics), lenses to generate magnified images of small objects. Optical microscopes ...
.
History
The procedure was designed by Alice B. Schaeffer and MacDonald Fulton, two microbiologists at Middlebury College
Middlebury College is a Private university, private Liberal arts colleges in the United States, liberal arts college in Middlebury, Vermont, United States. Founded in 1800 by Congregationalism in the United States, Congregationalists, Middlebury w ...
, during the 1930s. The procedure also goes by the name ''Wirtz-Conklin method'', referring to two bacteriologists during the 1900s.
See also
* Moeller stain
References
Staining
Microbiology techniques
Bacteriology
Microscopy
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