1. Define Capsule, Slime layer, S layer, and glycocalyx.
An outer viscous covering around the cell wall of some bacteria whiclh consists of polysaccharide or polypeptide or glycoprotein is called a capsule.
An outer zone of diffused unorganized material around the cell wall of sone bacteria which can be easily removed by washing is called a slime layer.
A regulatory structured layer consisting of crystaline protein, which occurs in the surface of certain Gram-positive and Gram-negative bactéria is càlled S – layer. It is also seen in certain Archacobacteria.
The glycocalyx is an outer covering that includes capsule, slime layer, and S- layer.
2. Name a few bacteria which produce capsule.
Capsules are found in Streptococcus pneumoniae, Klebsiella pneumoniae, Haemophilus influenzae, Enterobacter species, Bacillus species, Escherichia coli KI, Neisseria meningitidis, Alcaligenes faecalis, Azotobacter species, etc.
3. What is the role of 20% copper sulfate in capsuļe staining?
The capsule being nónionic has very little affinity for stains. Since the capsule is, water-soluble, 20% copper sulfate solution rather than water is used to wash the purple primary stain out of the nonionic capsular material without removing the stain that is bound to the cell wall… It also acts as a counterstain as it is absorbed into the decolorized capsular material.” Some of the stains is retained in the capsule, giving it a light blue / violet color.
4. Name the methods used for capsule staining.
- (a) Hiss’s method. Activate Windows
- (b) Maneval’s method. Go to Settings to activate Windows
- (c) Howie and Kirkpatrick method.
5. What precautions should be taken while performing capsule staining?
The precautions to be taken to get good results in capsule staining are:
- (a) The smear should not be heat fixed.
- (b) Vigorous washing should be avoided, as it can dislodge the water-soluble capsular material.
- (b) Prepare suspension or smear using dilute sugar solution.
6. What is meant by an extracellular polysaccharide (EPS)?
A glycocalyx made up of sugars is called EPS
7. What is the role of a capsule?
Capsule serves the following functions:
- (i) contributes to virulence (the degree of pathogenicity) of bacteria. (Pathogenicity means ability to produce disease).
- (ii) protects bacteria against phagocytosis by the phagocytic cells of the host defense mechanism.
- (iii) helps in the formation of multicellular aggregates and adherence to the surfaces of host cells or tissues, e. g., bacteria producing dental plaques/caries adhere: to the teeth
- (iv) protects the cell against temporary drying by binding water molecules.
- (v) may serve as a reservoir for stored food.
8. What is the significance of demonstrating capsules in medical microbiology?
The presence of the capsule indicates that the bacteria are virulent.
9. Which is the simplest method for demonstrating capsules?
Capsules can be easily demonstrated ac clear zone against dark background usind wet INDIA INK (negative staining). In this method, capsules do not become shrunken as heat is not used.