The study by Guennadi Sezonov, Danièle Joseleau-Petit, and Richard D'Ari investigates the physiology of *Escherichia coli* in Luria-Bertani broth. They found that steady-state growth in this medium ceases at an optical density (OD600) of 0.3, despite the broth supporting growth up to an OD600 of 7. The growth rate slows down and cell mass decreases, indicating a lack of utilizable carbon source. The carbon sources in Luria-Bertani broth are catabolizable amino acids, not sugars. The authors conducted experiments to confirm that the broth lacks fermentable sugars and contains high concentrations of catabolizable amino acid equivalents, which are depleted during the post-exponential phase of growth. They also noted that the physiological state of the cells varies significantly during this period, and the composition of the broth can affect the reproducibility of results. The study highlights the importance of understanding the specific conditions under which *E. coli* grows optimally in Luria-Bertani broth.The study by Guennadi Sezonov, Danièle Joseleau-Petit, and Richard D'Ari investigates the physiology of *Escherichia coli* in Luria-Bertani broth. They found that steady-state growth in this medium ceases at an optical density (OD600) of 0.3, despite the broth supporting growth up to an OD600 of 7. The growth rate slows down and cell mass decreases, indicating a lack of utilizable carbon source. The carbon sources in Luria-Bertani broth are catabolizable amino acids, not sugars. The authors conducted experiments to confirm that the broth lacks fermentable sugars and contains high concentrations of catabolizable amino acid equivalents, which are depleted during the post-exponential phase of growth. They also noted that the physiological state of the cells varies significantly during this period, and the composition of the broth can affect the reproducibility of results. The study highlights the importance of understanding the specific conditions under which *E. coli* grows optimally in Luria-Bertani broth.