LB (Lysogeny broth)is the most commonly used nutrient medium in microbiology experiments for culturing bacteria such as E. coli, and is divided into liquid medium and solid medium made by adding agar. LB medium with antibiotics added can be used to screen selected colonies with E. coli as the host.


The method for the preparation of 1 litre of LB:

  • Measure out the following:
    • 10 g tryptone
    • 5 g yeast extract
    • 10 or 5 or 0.5 g NaCl as required (see Formulae above; some bacteria are sensitive to NaCl)
  • Suspend the solids in ~800 mL of distilled or deionized water.
  • Add further distilled water or deionized water, in a measuring cylinder to ensure accuracy, to make a total of 1 liter.
  • Autoclave at 121°C for 20 mins.
  • After cooling, swirl the flask to ensure mixing, and the LB is ready for use.

Because 1 L of LB is too much for our experiment, we’ve divided each dosage by 4

  • 250 mL of distilled water
  • 2.5 g of tryptone
  • 1.25 g of yeast extract
  • 2.5 g of NaCl

Yeast extract peptone dextrose (YEPD) is a complete medium for yeast growth. It contains yeast extract, peptone, double-distilled water, and glucose (dextrose). It can be used as solid medium by including agar. The yeast extract will typically contain all the amino acids necessary for growth.


Yeast extract 10 g

Tryptone 20 g

Dexyrose 20 g

1000 mL of distilled water


We’ve also divide each dosage by 4:

Yeast extract 2.5 g

Tryptone 5 g

Dexyrose 5 g

250 mL of distilled water


medium into petri dish in the clean bench.