Macromolecular composition of bacteria

Equations are presented that describe the macromolecular composition in exponential bacterial cultures as functions of five parameters: doubling time of the culture (τ), protein per origin of replication (P₀), chromosome replication time (C-period), peptide chain elongation rate (c_p), and the time between termination of replication and cell division (D-period). Implicit in the value for some of these parameters is a specific macromolecular control system: the control of the growth rate (τ), the timing of initiation of rounds of chromosome replication (P₀), and the regulation of cell division (D). The utility of these relations is illustrated by using updated measurements of the macromolecular composition of E. coli B/r to calculate values for the fundamental parameters and to predict the composition of a mutant which has a defect in the control of DNA replication. Furthermore, the meaning of several often-cited physiological parameters (RNA/protein, RNA/cell and RNA/genome) is examined. The relations presented here show that these parameters and their variation with growth rate are not directly relevant to arguments about control of ribosome synthesis or culture growth.