title: Optimality and sub-optimality in a bacterial growth law.
abstract: Organisms adjust their gene expression to improve fitness in diverse environments. But finding the optimal expression in each environment presents a challenge. We ask how good cells are at finding such optima by studying the control of carbon catabolism genes in Escherichia coli. Bacteria show a growth law: growth rate on different carbon sources declines linearly with the steady-state expression of carbon catabolic genes. We experimentally modulate gene expression to ask if this growth law always maximizes growth rate, as has been suggested by theory. We find that the growth law is optimal in many conditions, including a range of perturbations to lactose uptake, but provides sub-optimal growth on several other carbon sources. Combining theory and experiment, we genetically re-engineer E. coli to make sub-optimal conditions into optimal ones and vice versa. We conclude that the carbon growth law is not always optimal, but represents a practical heuristic that often works but sometimes fails.
authors.affiliation: Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Towbin
authors.affiliation: Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Yael
authors.initials: Y
authors.lastname: Korem
authors.affiliation: Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Anat
authors.initials: A
authors.lastname: Bren
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Shany
authors.initials: S
authors.lastname: Doron
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Rotem
authors.initials: R
authors.lastname: Sorek
authors.affiliation: Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Uri
authors.initials: U
authors.lastname: Alon
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D001692:Biological Transport; D002244:Carbon / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D005818:Genetic Engineering
chemical_list: D029968:Escherichia coli Proteins; D002244:Carbon