Fig. 1 |. RNa-to-protein ratio is both growth-rate and nutrient dependent.

a, Schematic flow of nutrients for biomass formation. Carbon (C) and nitrogen (N) combine to make amino acids. Amino acids combine with carbon precursors and phosphorus (P) to make nucleic acids. b, RNA-to-protein ratios for chemostat cultures under C, N and P limitations at different growth rates. Each data point shows the mean value from three technical replicates. c, Translation elongation rates (amino acids per second) as measured by the lacZ induction assay after correction for translation initiation. The bar height represents mean values with error bars as s.e.m. from three biological replicates. d, Polysome profiles of cells grown under C, N and P limitations in chemostats at a dilution rate of 0.1 h⁻¹. Five independent experiments were repeated, with a single representative curve shown. e, Quantification of ribosomes in the form of subunits (30 S +  50 S), free 70 S, mRNA-bound 70 S (one ribosome on one mRNA) and polysomes (multiple ribosomes on one mRNA). The bar height represents mean values with error bars as s.e.m. from three biological replicates. f, Cells adapt to different nutrient limitations using different strategies of translational regulation that achieve the same protein production rate.