Optimization of BioExpress supplementation of M9 cultures

Uniform labeling of proteins with 15N and 13C has typically been achieved through the use of bacteria grown in minimal media, such as M9, which contain single nitrogen and carbon sources. While this arrangement facilitates the straightforward isotopic replacements of these elements, the growth characteristics of Escherichia coli (E. coli) in these media are somewhat compromised compared to growth in rich media. These effects typically include a drop in maximum cell density, requiring that larger cultures be grown to produce sufficient quantities of protein for NMR study.

To avoid the increased expense and time required to prepare, grow, and process such larger cultures, an alternative approach is to supplement minimal media with mixtures of isotopically labeled biomolecules, such as cell lysates. In this application note, Cambridge Isotope Laboratories evaluates the effects of adding increasing amounts of one such mixture, BioExpress^® Cell Growth media to E. coli cultures grown in M9 minimal media.