The main components of most E. coli media are:-

• Tryptone, enzymatic digest of casein.
  Tryptone is a pancreatic digest of casein. Casein is the main protein of milk and is a rich source of amino acid nitrogen. Amongst all amino acids especially the Tryptophan is present in high concentrations.
  Due to the rich nutritional properties, Tryptone is added to media as an accelerator to increase the yield of organisms and is recommended where a rapid and luxuriant growth of micro organisms is required.

• Yeast extract
  Yeast Extract is a spray dried extract manufactured by complete autolysis, i.e. a transformation of proteins into peptides and amino acids, implemented through the proteolytic enzymes present in yeast cells.
  The cell membranes are discarded, enabling completely soluble yeast extracts to be obtained. In LB media Yeast extract is an essential nitrogen source for bacteria besides peptides and amino acids.  Yeast extract also contains purine and pyrimidine bases, carbohydrates and water soluble vitamins of B group.

• Glucose
  As the main carbon source
• Sodium chloride
  To set the osmolarity of the medium at a suitable osmotic environment.
• Agar
  When added, to solidify the medium.
• Additives
  Like Casamino acids, Magnesium sulfate, Maltose, Thymidine.

In fact most E. coli media do contain these components, but all in different compositions and ratios to obtain an optimal result for cell growth and yield, propagation of bacteriophages and preparation of competent cells.