Complex media

Pasteur, Koch, and Tyndall typically prepared media by boiling animal or plant materials to extract nutritive molecules. Modern complex media contain extracts of beef (peptone), milk (tryptone), soybean meal (soytone) or yeast. the protein in these extracts are broken down into small peptides and amino acids. the specific amount of these molecules is not precisely determined their wide assortment allows complex media to support a wide range of bacterial types.