It is an enzymatic digest of animal protein. Peptone is the principal source of organic nitrogen for the growing bacteria.
0.3% beef extract/yeast extract
It is the water-soluble substances which aid in bacterial growth, such as vitamins, carbohydrates, organic nitrogen compounds and salts.
1.5% agar
It is the solidifying agent.
0.5% NaCl
The presence of sodium chloride in nutrient agar maintains a salt concentration in the medium that is similar to the cytoplasm of the microorganisms.
Distilled water
Water is essential for the growth of and reproduction of micro-organisms and also provides the medium through which various nutrients can be transported.