ZymoBroth (ZB) is a specially formulated growth medium used for the preparation of highly competent E. coli cells for DNA transformation. When compared to classic SOB growth medium, ZymoBroth dramatically increases transformation efficiency, typically on the order of 5 - 100 fold (depending on the E. coli strain). As part of our popular Z-Competent E. coli Transformation Kit, ZB enables researchers to generate their own homemade Z- Competent E. coli for DNA transformation. ZB medium has been tested on a wide range of E. coli strains. Our data indicate that ZB medium stimulates the transformation efficiency of all E. coli strains tested, including K12 derivatives (Such as JM109, HB101, etc.) and B strain derivatives (such as BL21, etc.).