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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 ...
In culture, they may appear as cocci, or as bacilli up to 6-8 μm long. [citation needed] The bacteria stain Gram-positive, acid-fast. The cell wall contains as high as 60% lipid, giving the mycobacteria their hydrophobic characteristics, slow growth, and resistance to desiccation, disinfectants, acids, and antibodies. (Mycobacterium family ...
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 .
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.
Mechanism of acid-fast staining in acid-fast cells and non-acid-fast cell [24] [25] [26] 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.
Both gram-positive and gram-negative bacteria commonly have a surface layer called an S-layer. In gram-positive bacteria, the S-layer is attached to the peptidoglycan layer. Gram-negative bacteria's S-layer is attached directly to the outer membrane. Specific to gram-positive bacteria is the presence of teichoic acids in the cell wall. Some of ...
Since this genus has cell walls with a waxy lipid-rich outer layer containing high concentrations of mycolic acid, [4] acid-fast staining is used to emphasize their resistance to acids, compared to other cell types. [5] Mycobacterial species are generally aerobic, non-motile, and capable of growing with minimal nutrition.
Some bacteria have cell walls which are particularly adept at retaining stains. These will appear positive by Gram stain even though they are not closely related to other gram-positive bacteria. These are called acid-fast bacteria, and can only be differentiated from other gram-positive bacteria by special staining procedures. [25]