Question

What is a bacterial smear?

Answer 1

A bacterial smear is defined as the thin layer of bacteria that is placed on a slide for staining purposes. This helps us to visualize the bacteria using a microscope and to study its morphological characteristics.

Complete answer:
The preparation of bacterial smear involves several steps such as-
1. Glass slide preparation- the glass slide on which the smear is to be made is made grease free by washing with soap and water and rinsing with alcohol.
2. Preparation of smears- an even smear having a diameter of 15-20mm must be prepared. If the preparation of smear broth culture is being used then it can be spread directly using an inoculation loop. But if the smear is being made from solid culture then a drop of water needs to be placed on the slide first following which cells from the culture are mixed with the water to form the smear.
3. Air dry- after the smear is made it should be allowed to dry so that it forms a thin whitish layer on the slide.
4. Fixation of the smear- the final step is the heat fixation of the smear where the air dried smear is placed over the flame which allows proper fixation.

Note-
After the bacterial smear is made it is generally stained with different dyes that are used in staining of bacteria. These dyes add contrast to the bacterial cells so that they can be easily visualized through the microscope. One of the most famous staining methods for bacteria is Gram Staining.