Nutrient Agar is a general-purpose, nutrient medium used for the cultivation of microbes supporting the growth of a wide range of non-fastidious organisms. Nutrient agar is popular because it can grow a variety of types of bacteria and fungi, and contains many nutrients needed for bacterial growth.
Composition of Nutrient Agar
1. 0.5% Peptone
2. 0.3% beef extract/yeast extract
3. 0.5% NaCl
4. 1.5% agar
5. Distilled water (To make the media volume 1000ml)
Peptone: It is an enzymatic digest of animal protein. Peptone is the principal source of organic nitrogen for the growing bacteria.
Beef extract/yeast extract: It is the water-soluble substances that aid in bacterial growth, such as vitamins, carbohydrates, organic nitrogen compounds, and salts.
Agar is the solidifying agent.
The presence of sodium chloride in nutrient agar maintains a salt concentration in the medium that is similar to the cytoplasm of the microorganisms.
Water is essential for the growth of and reproduction of micro-organisms and also provides the medium through which various nutrients can be transported.
Preparation of Nutrient Agar
1. Suspend the required amount of different components of nutrient agar media in 1 liter of distilled water.
2. Fully dissolve all components.
3. Autoclave the dissolved mixture at 121 degrees Celsius for 15 minutes.
4. Once the nutrient agar has been autoclaved, allow it to cool but not solidify.
5. Pour nutrient agar into each plate and leave plates on the sterile surface until the agar has solidified.
6. Replace the lid of each Petri dish and store the plates in a refrigerator.
Uses of Nutrients Agar
It is frequently used for the isolation and purification of cultures.
It can also be used as a means for producing the bacterial lawns needed for antibiotic sensitivity tests. In actuality, antibiotic sensitivity testing is typically performed on media specially formulated for that purpose.