Add oil immersion to the stained area and observe it under the microscope using a 100X objective.Later, remove the extra stain by tilting a glass slide. Flood a smear with the crystal violet stain and leave it for 30 seconds.Then, allow the smear to air dry (do not heat fix the smear, as it may result in cell shrinkage that in turn can distort the bacterial capsule).Prepare a smear by taking an inoculum from the bacterial culture and mix it with a drop of India ink.Add a drop of India ink to the centre of the glass slide.Take a clean, sterilized or grease-free slide.India ink method involves the following steps: India ink is a negative stain that will stain the positively charged background. Crystal violet is a positive stain that will stain the negatively charged bacterial cell. ![]() a basic stain ( Crystal violet) and an acidic stain ( India ink). India ink method uses two types of stain, i.e. The capsule staining employs various techniques, among which the most common methods are: Differential capsule stains are available to highlight the specific structure (like capsule) in a bacterial cell. The other approach of capsule staining is to stain the capsule by leaving a bacterial cell and background colourless. Thus, capsule staining creates contrast by staining a bacterial cell along with its background and leaving a capsule as a colourless halo. A capsule being non-ionic will not stain by either of the two dyes. The principle of capsule staining is based on staining of background with an acidic stain and staining of bacterial cell with a basic stain. The addition of serum provides a more unobstructed view of a capsule under a light microscope. To enhance the capsule’s size or increase its visibility, we can also add a drop of serum. In addition to this, avoid steps like washing or rinsing because it can dislodge the bacterial cell capsule. To stain a capsule, we need a special capsule stain that can focus on the capsule.Ī capsule can be easily destroyed by heat treatment, due to which a step of heat fixing is skipped in capsule staining. The basic dye will stain the negative bacterial cell, and an acidic stain will stain the positive background. it will neither take up the colour of acidic stains nor basic stains. The bacterial capsule is non-ionic in nature, i.e. The microcapsule has a size of less than 0.2 µ, whereas the macrocapsule has a size of more than 0.2µ. Capsule are of two types, namely micro and macro capsule. Capsules are the structures clearly visible under the light microscope after they get stained via differential capsule stain.īacteria may possess a capsule ( capsulated bacteria) or lack a capsule ( non-capsulated bacteria). The formation of a capsule is a process controlled genetically. ![]() In the majority, a capsule consists of polysaccharides, but a few may possess polypeptides or glycoproteins. The capsule also acts as a virulence factor and is responsible for the pathogenicity of many microorganisms like Streptococcus pneumoniae, Escherichia coli, Neisseria meningitis etc. A mucus layer also protects a cell from phagocytosis. The cytoplasm of bacteria partially forms a capsule, which then migrates to the cell wall, and there it exists as a mucous or slime covering.Ī bacterial capsule protects a cell from desiccation because of its mucous content. ![]() The capsule or glycocalyx is composed of glycoproteins. Capsule staining can be performed by employing India ink, Anthony’s, Maneval’s and Hiss method.Ī bacterial capsule refers to the mucilaginous coating that surrounds the cell wall of bacteria. Thus, it becomes necessary to identify the presence of an extracellular capsule. It is an important staining method because some bacteria like Bacillus anthracis, Streptococcus pneumoniae etc., have a capsule, which can cause pathogenicity in humans and animals. Content: Capsule StainingĪ capsule staining is a special staining method, which uses differential capsule stains that either highlight the capsule or stains the bacterial cell along with the background. Here, you will get to know the definition, principle, different methods and significance of the capsule staining, along with the meaning of bacterial capsule. Thus, by knowing the presence of the capsule, we can determine the degree of pathogenicity. It is necessary to perform capsule staining because a capsule’s presence indicates a virulent strain of bacteria that can cause disease.
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