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When starch is mixed with iodine in solution, an intensely dark blue colour develops, representing a starch/iodine complex. Starch is a substance common to most plant cells and so a weak iodine solution will stain starch present in the cells. Iodine is one component in the staining technique known as Gram staining, used in microbiology.
Gram stain of Candida albicans from a vaginal swab. The small oval chlamydospores are 2–4 μm in diameter. Gram staining is a bacteriological laboratory technique [8] used to differentiate bacterial species into two large groups (gram-positive and gram-negative) based on the physical properties of their cell walls.
Narrow spectrum fungal stains are selective, and they can help differentiate and identify fungi. [10] The results of Ziehl–Neelsen staining is variable because many fungal cell walls are not acid fast. [11] An example of a common type of acid-fast fungus that is usually stained with Ziehl–Neelsen staining is called Histoplasma (HP). [12]
[1] [2] Once stained as part of a sample, these organisms can resist the acid and/or ethanol-based decolorization procedures common in many staining protocols, hence the name acid-fast. [ 2 ] The mechanisms of acid-fastness vary by species although the most well-known example is in the genus Mycobacterium , which includes the species ...
Diplorickettsia massiliensis grown in XTC-2 cells, Gimenez staining. The Gimenez staining technique uses biological stains to detect and identify bacterial infections in tissue samples. Although largely superseded by techniques like Giemsa staining, the Gimenez technique may be valuable for detecting certain slow-growing or fastidious bacteria.
Gram-negative bacteria will stain a pink color due to the thin layer of peptidoglycan. If a bacteria stains purple, due to the thick layer of peptidoglycan, the bacteria is a gram-positive bacteria. [4] In clinical microbiology numerous other staining techniques for particular organisms are used (acid fast bacterial stain for mycobacteria).
Clusters of bacteria (arrow) shown on Warthin–Starry stain. The Warthin–Starry stain ( WS ) is a silver nitrate -based staining method (a silver stain ) used in histology. It was first introduced in 1920 by American pathologists Aldred Scott Warthin (1866–1931) and Allen Chronister Starry (1890–1973), for the detection of spirochetes .
Special staining techniques such as Albert's or Neisser's demonstrate the granules more clearly. Volutin granules are characteristically present in diphtheria bacilli. Their function is uncertain.