2xYT Broth is a nutritious microbial growth medium designed for the cultivation of recombinant strains of Escherichia coli. It is also commonly used for the propagation of the M13 bacteriophage for research. The high proportions of Tryptone and yeast extract in this medium provide the necessary nitrogen and growth factors that the bacteriophage requires to multiply quickly and in high density without depleting the host cells of these critical nutrients.   

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 2xYT 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.