Hiroshi Nakaido, PBD Faculty Scientist, Structural Biology Department, and Professor of Biochemistry and Molecular Biology, UC Berkeley, has authored a guest post on the Small Things Considered Blog regarding the limitations of LB medium.
"LB broth contains, per ml, 10 mg tryptone (a mixture of peptides formed by the digestion of casein with the pancreatic enzyme, trypsin), 5 mg yeast extract (an autolysate of yeast cells), and 5 or 10 mg NaCl... While this may appear a tasty dish for many bacteria of research interest, it is an inappropriate choice for physiological studies wherein reproducibility is required. Since only bacterial cultures in balanced growth (achieved by sufficient time in exponential growth) have a reproducible average cell size and chemical composition, none of the components of liquid media should become exhausted during growth of the culture. Is this the case with LB broth? To answer this question, we must know what limits bacterial growth in LB broth."
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