Luria Broth (Miller’s LB Broth) is a nutritious medium designed for the growth and maintenance of recombinant strains of Escherichia coli. E.coli grows to the late log phase and strains are typically derived from E.coli K12. This strain has been modified by specific mutation into an auxotrophic strain incapable of growth in nutrient-deficient media. Luria Broth provides all the nutritional factors to support luxurious growth of E.coli so that the cells do not need to synthesize them on their own.  

Typically growth in broth is measured visually, or by measuring the optical density of the broth after incubation. While these are considered acceptable methods, for this analysis Alpha Biosciences’ QC laboratory took another approach to obtain more quantified results. We performed a Growth Comparison test by inoculating prepared duplicate tubes of each leading commercial provider’s Luria Broth in parallel, with pure ATCC cultures and incubated for 24 hours. Next, we sub-cultured equal aliquots of equally serial-diluted suspensions of the cultured broth onto duplicate Standard Methods Agar (SMA). We incubated the inoculated SMA plates for 24 hours and counted all plates with 30-300 colonies, and averaged the duplicates. We then calculated the growth increase as cfu/mL of each strain for each provider and graphed the results.