gram positive vs gram negative cells on a slide

Polysaccharide capsules and slime layers are generally difficult to stain selectively. Finazzo, Broward Community College–Central campus, Davie, FL) Due to the age of the culture, endospores have been released from the cells. cereus are in red endospores are in green. Endospore stain of a Bacillus cereus culture using the Shaeffer-Fulton method and viewed at 1,000x total magnification under an oil immersion lens. Endospores stain with malachite green vegetative cells stain with safranin (red).Endospores resist staining with basic stains.Microscopic examination of stained endospores will reveal their relative size and position in the cell, which are distinctive characteristics of each of the spore-forming species.

Vegetative cells are then counterstained with safranin. Malachite green is water soluble and has a low affinity for cellular material, so vegetative (actively dividing) cells may be decolorized with water. In the Schaeffer-Fulton method, a primary stain with malachite green is forced into the endospore by steaming the bacterial emulsion. The nature of the spore makes it impervious to most ordinary stains and staining methods, but, once stained it strongly resists decolorization and counterstaining. This stain is used to visualize bacterial endospores produced by members of the genera Bacillus and Clostridium. (Alan Schenkel, Peter Justice, and Erica Suchman, Colorado State University, Fort Collins, CO ) A mixed culture of Mycobacterium smegmatus (acid-fast, red/pink) and Staphylococcus epidermidis (non-acid-fast, light blue/purple).

Acid-fast organisms resist decolorization with acid-alcohol.

Developed to detect the bacterial species that causes tuberculosis.

A differential stain used to detect bacteria with mycolic acid cell walls (genera Mycobacterium and Nocardia).

The decolorized non-acid-fast cells then take up the counterstain.

The smear is then rinsed with a very strong decolorizer, which strips the stain from all non-acid-fast cells but does not permeate the cell wall of acid-fast organisms. This is further assisted by the addition of heat. The primary stain used in acid-fast staining, carbolfuchsin, is lipid-soluble and contains phenol, which helps the stain penetrate the cell wall. (1)īecause the cell wall is so resistant to most compounds, acid-fast organisms require a special staining technique. Acid-fast organisms are highly resistant to disinfectants and dry conditions. The acid-fast stain is a differential stain used to identify acid-fast organisms such as members of the genus Mycobacterium .Īcid-fast organisms are characterized by wax-like, nearly impermeable cell walls they contain mycolic acid and large amounts of fatty acids, waxes, and complex lipids.

Gram positive vs gram negative cells on a slide