What are the types of staining techniques?
- Types of staining techniques. Simple staining.
- Differential staining. (Use of of single stain)
- (Use of two contrasting stains) Direct.
- Indirect. Separation.
- Visualization. (Positive)
- (Negative) into groups. of structures.
- Gram stain. Flagella stain.
- Acid fast. Capsule stain.
What are the basic components of stains?
A stain consists of three constituents: the organic compound containing a benzene ring, the chromophore, and the auxochrome. Thus a stain (Fig. 17.1) may be defined chemically as an organic compound containing both chromophore and auxochrome groups linked to its benzene ring.
Is haematoxylin acidic or basic?
Haematoxylin can be considered as a basic dye. It is used to stain acidic structures a purplish blue. DNA in the nucleus, and RNA in ribosomes and in the rough endoplasmic reticulum are both acidic, and so haemotoxylin binds to them and stains them purple.
Is Safranin acidic or basic?
Safranin is a basic biological dye commonly used as a counter-stain in some of the staining protocols like gram staining. Following are the chemical and physical properties of the safranin.
What is negative staining technique?
From Wikipedia, the free encyclopedia. In microscopy, negative staining is an established method, often used in diagnostic microscopy, for contrasting a thin specimen with an optically opaque fluid. In this technique, the background is stained, leaving the actual specimen untouched, and thus visible.
What is the purpose of negative stain?
Purpose: Negative stains are used to view cell morphology and arrangement of microorganisms and selected because of the minimal damage and distortion of the bacterial structures. Acidic stains such as Nigrosin are used in the staining process.
Which structure requires a negative staining technique?
Negative staining is used when it is important to be able to view the bacteria without using harsh stains or performing the heat fixing technique that could possibly distort or change the shape of the bacteria. It is used when looking at capsules and yeast or spirochetes that do not stain well.
Is capsule stain positive or negative?
This is a negative staining technique that is essentially used to identify the presence of capsules. Because of its acidic nature, India ink (or Congo red, nigrosin) stains the background dark.
What does a negative capsule stain look like?
Principle of Capsule Staining Negative staining methods contrast a translucent, darker colored, background with stained cells but an unstained capsule. The background is formed with india ink or nigrosin or congo red. Capsules appear colourless with stained cells against dark background.
What is the staining method of choice for bacterial capsules?
Bacterial capsules are non-ionic, so neither acidic nor basic stains will adhere to their surfaces. Therefore, the best way to visualize them is to stain the background using an acidic stain and to stain the cell itself using a basic stain. We use India ink and Gram crystal violet.
How does having a capsule benefit a bacterium?
Capsules can protect a bacterial cell from ingestion and destruction by white blood cells (phagocytosis). While the exact mechanism for escaping phagocytosis is unclear, it may occur because capsules make bacterial surface components more slippery, helping the bacterium to escape engulfment by phagocytic cells.
What is a bacterial capsule and what is its purpose?
The capsule helps the bacteria to adhere to surfaces, camouflages the bacteria from the immune system by mimicking the host tissues, and makes the bacteria resistant to complement invasiveness. A capsule protects cells from desiccation and toxic metabolites in the environment (heavy metal ions and free radicals).
What is the function of the capsule?
It has several functions: promote bacterial adhesion to surfaces or interaction with other organisms; act as a permeability barrier, as a defense mechanism against phagocytosis and/or as a nutrient reserve. Among pathogens, capsule formation often correlates with pathogenicity.
How do you know if a bacteria has a capsule?
To visualize encapsulated bacteria using a microscope, a sample is treated with a dark stain, such as India ink. The structure of the capsule prevents the stain from penetrating the cell. When viewed, bacterial capsules appear as a bright halo around the cell on a dark background.
What is a bacterial smear?
A bacterial smear is a thin layer of bacteria placed on a slide for staining. Preparing the smear requires attention to a number of details that help prevent contamination of the culture and ensure safety to the preparer.
Why is it important to use a small amount of bacteria when preparing a smear?
Just as in preparing a smear, you only need a small amount of organism. If you have too many organisms, you won’t be able to see the morphology of individual cells. It is also important not use too much nigrosin. If it is too thick, the background will have a cracked appearance similar to mud puddles drying in the sun.
What is the purpose of bacterial smear?
The purpose of making a smear is to fix the bacteria onto the slide and to prevent the sample from being lost during a staining procedure. A smear can be prepared from a solid or broth medium. Below are some guidelines for preparing a smear for a Gram-stain.
What is the difference between a direct stain and a negative stain?
1) What is the difference between a direct stain and negative stain? A direct stain uses basic stains (positively charged), where the objective is to stain the bacterium itself. A negative stain is used to stain the background, but leave the bacteria unstained using an acid stain.
What color is Gram positive?
blue
Why is it important to know Gram positive or negative?
If bacteria are present, this test can also help your doctor learn if the bacteria are gram negative or gram positive. The difference between gram-negative and gram-positive bacteria can affect their recommended treatment plan. Gram stains can be performed on various types of specimens, including: blood.
What is difference between gram positive and negative?
The gram-positive bacteria retain the crystal violet colour and stains purple whereas the gram-negative bacteria lose crystal violet and stain red. Thus, the two types of bacteria are distinguished by gram staining. Gram-negative bacteria are more resistant against antibodies because their cell wall is impenetrable.
How can you tell the difference between gram positive and negative bacteria?
Most bacteria can be broadly classified as Gram positive or Gram negative. Gram positive bacteria have cell walls composed of thick layers of peptidoglycan. Gram positive cells stain purple when subjected to a Gram stain procedure. Gram negative bacteria have cell walls with a thin layer of peptidoglycan.