LB Agar (Lennox) BD Difco™ 500 g. A nutritionally rich media developed by Lennox for the growth and maintenance of pure cultures of recombinant strains of E. coli. These strains are generally derived from E. coli K12, which are deficient in B vitamin production. 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. LB Agar, Lennox provides all the nutritional requirements of these organisms. LB Agar, Lennox contains half the sodium chloride level of the Miller formulation of LB Agar. This allows the researcher to select the optimal salt concentration for a specific strain.