Escherichia coli physiology in Luria-Bertani broth

Abstract

Luria-Bertani broth supports Escherichia coli growth to an optical density at 600 nm (OD(600)) of 7. Surprisingly, however, steady-state growth ceases at an OD(600) of 0.3, when the growth rate slows down and cell mass decreases. Growth stops for lack of a utilizable carbon source. The carbon sources for E. coli in Luria-Bertani broth are catabolizable amino acids, not sugars.

FIG. 1.

Growth of E. coli MG1655 in Luria-Bertani broth. An overnight culture was diluted 5,000-fold in Luria-Bertani broth and cultivated at 37°C with vigorous aeration. (A) The OD₆₀₀ (triangles) and cell concentration (crosses) were measured periodically. (B) The ratio of the OD₆₀₀ to the cell concentration was calculated at each point and multiplied by 10⁹.

FIG. 2.

Growth response to d-glucose in exhausted Luria-Bertani medium. Filter-sterilized LB* medium was supplemented with various concentrations of d-glucose, inoculated with MG1655, and incubated for 24 h at 37°C with vigorous aeration. The OD₆₀₀ of each culture was measured.

FIG. 3.

Bioassay for l-leucine. A culture of a leu-82::Tn10 derivative of MG1655 was grown in M63 glucose minimal medium containing l-leucine. Cells were resuspended in M63 and diluted 4,000-fold into M63 glucose containing increasing concentrations of l-leucine (A) or of Luria-Bertani broth (LB) (B).