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Certain Actinobacteria (especially aerobic ones in the order Mycobacteriales) with mycolic acid in their cell wall; not to be confused with Actinomyces, which is a non-acid-fast genus of actinomycete. Note that Streptomyces do not contain mycolic acid. Nocardia (weakly acid-fast; resists decolorization with weaker acid concentrations ...
Mechanism of acid-fast staining in acid-fast cells and non-acid-fast cell [23] [24] [25] The mechanism of action of the Ziehl-Neelsen stain is not completely understood, but it is thought to involve a chemical reaction between the acidic dyes and the cell walls of the bacteria.
The genus is acid-fast to some degree, it stains only weakly Gram positive. The most common form of human nocardial disease is a slowly progressive pneumonia, the common symptoms of which include cough, dyspnea (shortness of breath), and fever. It is not uncommon for this infection to spread to the pleura or chest wall.
[7] [12] The diderm bacteria can also be further differentiated between simple diderms lacking lipopolysaccharide (LPS); the archetypical diderm bacteria, in which the outer cell membrane contains lipopolysaccharide; and the diderm bacteria in which the outer cell membrane is made up of mycolic acid (e. g. Mycobacterium). [9] [10] [12] [13]
Schematic of typical Gram-positive cell wall showing arrangement of N-Acetylglucosamine and N-Acetylmuramic acid; Teichoic acids not shown.. The Gram-positive cell wall is characterized by the presence of a very thick peptidoglycan layer, which is responsible for the retention of the crystal violet dyes during the Gram staining procedure.
Bacillus subtilis . The cell wall of Bacillus is a structure on the outside of the cell that forms the second barrier between the bacterium and the environment, and at the same time maintains the rod shape and withstands the pressure generated by the cell's turgor. The cell wall is made of teichoic and teichuronic acids.
Although L-forms can develop from Gram-positive as well as from Gram-negative bacteria, in a Gram stain test, the L-forms always colour Gram-negative, due to the lack of a cell wall. The cell wall is important for cell division, which, in most bacteria, occurs by binary fission. This process usually requires a cell wall and components of the ...
Mycobacterium leprae is an intracellular, pleomorphic, non-sporing, non-motile, acid-fast, pathogenic bacterium. [3] It is an aerobic bacillus (rod-shaped bacterium) with parallel sides and round ends, surrounded by the characteristic waxy coating of mycolic acid unique to mycobacteria .