Luria Broth (Miller’s Modification)

These strains are generally derived from E. coli K12, which are unable to produce vitamin B, so this medium is formulated to enhance the growth of nutritionally demanding microorganisms. This strain of E. coli has been further modified through specific mutation to create an auxotrophic strain that is not capable of growth on nutritionally deficient media. Some plasmid vectors replicate to high copy numbers and do not require selective amplification. Some vectors do not replicate so freely and need to be selectively amplified. Antibiotics may be added to inhibit host synthesis and, as a result, prevent replication of the bacterial chromosome.

Tryptone provides nitrogen, vitamins, minerals and amino acids essential for growth. Yeast extract is the source of vitamins, particularly of the B-group. Sodium chloride supplies essential electrolytes for transport and osmotic balance.

Luria Broth (Miller’s Modification) has a different sodium chloride level than other media such as LB Broth (Lennox) (LC-1231) or Luria Broth (Miller’s LB Broth) (LC-1551). This allows selecting the optimum salt concentration of the medium for a specific strain.

Preparation

Suspend 15.5 grams of the medium in one litre of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Dispense into appropriate containers and sterilize in autoclave at 121 °C for 15 minutes.

Instructions for use

1. Carry out the experimental procedure according to appropriate use or purpose.
2. Inoculate and incubate at a temperature of 35 ± 2 °C for 18-24 hours.

• Miller J. H.: Experiments in Molecular Genetics, Cold Spring Harbor Laboratory (1972).