LB Growth Top Agar

Principle and Interpretation

LB-Growth Top Agar is recommended for the cultivation and maintenance of recombinant strains of Escherichia coli strains for the preparation of phage and plasmid DNA. LB Media, originally developed by Bertani, is a very common and nutritionally rich growth media for E. coli (1). This media is extensively used for the maintenance and propagation of plasmid DNA and for the growth of the recombinant strains which contain protein expression vector (2). The ingredients provide all the growth factors required for the E. coli strains. Tryptone provides all the required peptides and peptones. Yeast extract supplies all the essential vitamins, nucleotides, amino acids, carbohydrate and trace elements. Sodium chloride provides the sodium ions which help in the membrane transport and maintenance of osmotic equilibrium of the medium. Top agar is used to distribute bacteriophage and bacterial cells uniformly on the thin layer over the surface of a plate. Top agar contains less amount of agar than usual plates and so stays in a molten state for several days when it is kept at 45° to 50°C.