Differential Stain: Acid Fast: Ziehl-Neelson Method

Mycolic acids are long fatty acids found in the cell walls of the mycolata taxon, a group of bacteria that includes Mycobacterium tuberculosis, the causative agent of the disease tuberculosis. They form the major component of the cell wall of mycolata species. Despite their name, mycolic acids have no biological link to fungi; the name arises from the filamentous appearance their presence gives mycolata under high magnification. The presence of mycolic acids in the cell wall also gives mycolata a distinct gross morphological trait known as "cording." Mycolic acids were first isolated by Stodola et al. in 1938 from an extract of M. tuberculosis.
Mycolic acids are composed of a shorter beta-hydroxy chain with a longer alpha-alkyl side chain. Each molecule contains between 60 and 90 carbon atoms. The exact number of carbons varies by species and can be used as an identification aid. Most mycolic acids also contain various functional groups.
source: http://en.wikipedia.org/wiki/Mycolic_acid

Pleomorphism is the occurrence of two or more structural forms during a life cycle, especially of certain plants, including many marine plants such as Mastocarpus stellatus.
It can also apply at the species level.[1]
Cellular differentiation in multicellular organisms, where the young organism changes form when developing, is not considered pleomorphism, since only the new cells have a different form, while the original cell has been divided in two.
Extreme Pleomorphism is the claim that life forms can interchange among themselves between bacteria to viruses and fungi
Pertaining to the Bacteria- In the first decades of the 20th century, the term was used to refer to the supposed ability of bacteria to change shape dramatically or to exist in a number of extreme morphological (changing) forms. This claim sparked a controversy among the microbiologists and split them into two schools: the monomorphists, who opposed the claim, and the pleomorphists (such as Antoine Béchamp, Günther Enderlein or even Albert Calmette[1]).
Monomorphic theory, supported by Louis Pasteur, Rudolf Virchow, Ferdinand Cohn, and Robert Koch, emerged to become the dominant paradigm in modern medical science: it is now almost universally accepted that each bacterial cell is derived from a previously existing cell of practically the same size and shape. However it has recently been shown that certain bacteria are capable of dramatically changing shape, for example Helicobacter pylori exists as both a helix-shaped form (classified as a curved rod) and a coccoid form.
The modern-day definition of pleomorphism in the context of bacteria is now a variation of size or shape of the cell, rather than a change of shape as previously believed.
Extreme pleomorphism - where bacteria can turn into viruses and fungi has been claimed to be found in a 1970 paper by Virginia Livingston[2] However Livingston's findings have been discarded along with her treatment methods and cancer theory which has been disproved[3].
source; http://en.wikipedia.org/wiki/Pleomorphism

Acid-fastness is a physical property of some bacteria referring to their resistance to decolorization by acids during staining procedures.[1][2]
Acid-fast organisms are difficult to characterize using standard microbiological techniques (e.g. Gram stain - if you gram stained an AFB the result would be an abnormal gram positive organism, which would indicate further testing), though they can be stained using concentrated dyes, particularly when the staining process is combined with heat. Once stained, these organisms resist the dilute acid and/or ethanol-based de-colorization procedures common in many staining protocols—hence the name acid-fast.[2]
The high mycolic acid content of certain bacterial cell walls, like those of Mycobacteria, is responsible for the staining pattern of poor absorption followed by high retention. The most common staining technique used to identify acid-fast bacteria is the Ziehl-Neelsen stain, in which the acid fast bacilli are stained bright red and stand out clearly against a blue background. Another method is the Kinyoun method, in which the bacteria are stained bright red and stand out clearly against a green background. Acid-fast bacteria can also be visualized by fluorescence microscopy using specific fluorescent dyes (auramine-rhodamine stain, for example).[3] Some bacteria may also be partially acid-fast.
source; http://en.wikipedia.org/wiki/Acid-fast

CLICK IMAGE TO ENLARGE. Source: http://www.biozentrum.uni-wuerzburg.de/fileadmin/REPORT/BIOTE/biote016.htm
source: http://tube.medchrome.com/2011/06/zn-staining-technique-for-acid-fast.html
source: http://sites.google.com/site/scienceprofonline/virtualmicrobiologyclasslaboratory232

No comments:

Post a Comment

Related Posts Plugin for WordPress, Blogger...