The main components of most Esherichia 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 the amino acids, Tryptophan is present in the highest 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 Escherichia 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.
Crystal and molecular structure of RmlA Dr. Magnus S. Alphey, University of St. Andrews
Above 2 images: Crystals of MscS Dr. Magnus S. Alphey, University of St. Andrews