L B BROTH (Lennox)

LB Broth (Lennox) is a nutritionally rich medium developed by Lennox for the growth and maintenance of pure cultures of recombinant strains of E. coli used in molecular and microbiological procedures. These strains are generally derived from E. coli K12, which are unable to produce vitamin B, so this media 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.
Cultivation in LB Broth allows cells with an insert plasmid to start expressing the genes on the transformed plasmid, including the antibiotic resistance gene. If transformed E. coli are plated directly onto selective agar media (LB Agar containing antibiotic), fewer transformed colonies will appear per ml plated. Growing the transformed cells in LB broth will increase the number of transformed cells per ml. LB Broth (Lennox) contains ten times the sodium chloride level of Luria Broth (Miller?s Modification) and a half of the level found in Luria Broth (Miller?s LB Broth). This allows selecting the optimal salt concentration medium for a specific strain.

for propagation and maintenance of E.coli