Figure 1

Protein distributions. GFP fluorescence distributions in populations of bacteria (red) and yeast (black) measured under different conditions by flow cytometry. (a) High- and low-copy number (HC and LC respectively) regulatory promoters in bacteria and yeast: GFP expressed under the $LacO$ promoter on high (circles) and low (squares) copy number plasmids in bacteria, and under the GAL10 promoter on a high-copy plasmid (circles) and integrated into the genome (squares) in yeast. (b) Continuous (chemostats; circles) and batch cultures (diamonds) in bacteria and yeast: GFP expressed from high-copy number plasmids under the $LacO$ or GAL10 promoters, respectively. (c) Regulated (squares) and constitutive (x) promoters: In bacteria, $LacO$ promoter is compared to ColE1P1 promoter, both on low-copy number plasmids, and in yeast the GAL10 promoter is compared to ADH1, both integrated into the genome. All populations were grown in batch cultures. (d) Reporter GFP under GAL10 promoter (squares) and a functional HIS3-GFP N-terminal (stars) and C-terminal (triangles) tagged, both under the GAL1 promoter. All fluorescence levels in this figure were normalized such that the peak of the distributions appears at 1. The probability density is normalized to unit area. Note the logarithmic $y$ axis.Reuse & Permissions

Figure 2

(a) All distributions of Fig. 1 are plotted in units scaled by subtracting the mean and dividing by the standard deviation. The symbols represent different experiments as follows: $LacO$ promoter on a high-copy plasmid in bacteria (blue star—grown in chemostat, cyan triangle—in batch); the same on a low-copy plasmid in chemostat (red circle); GAL10 promoter on a high-copy plasmid in yeast (green triangle – grown in chemostat, magenta squares—in batch); the same integrated into the genome in chemostat (black cross); ADH1 promoter integrated into the genome in yeast grown in batch (blue diamond); ColE1P1 promoter on a low-copy plasmid in bacteria grown in batch (red triangle); Fused HIS3-GFP under GAL1 promoter in yeast in chemostat ($N$ terminal—cyan circles, C-terminal—black pentagram). The black line is the Frechet distribution best fit to the data, Eq. (4) with $k=0.095$, $m=-7.5$, and $s=7.09$.Reuse & Permissions

Figure 3

Relation between mean and variance. (a) Mean and variance for all experiments in bacteria that appear in Fig. 2 using the same symbols. (b) The same for yeast experiments. (c) Mean and variance for a large collection of experiments on yeast populations, where steady state protein distributions were measured by fluorescence microscopy [11]. GFP was expressed under the control of GAL10 on high or low-copy number plasmids, in different background strains grown in chemostat cultures with different dilution rates and limiting nutrients. Fits: $y=A{x}^2+Bx+C$ with the parameters: (a) $A=0.46$, $B=-0.39$, $C=0.1$. (b) $A=0.17$, $B=3.1$, $C=-1.54$. (c) $A=0.167$, $B=-0.31$, $C=-0.015$. The data are presented in three panels since fluorescence is not calibrated and therefore different sets of experiments performed under different conditions contain an arbitrary scale factor.Reuse & Permissions

Figure 4

Distributions under transient dynamics. Populations of bacteria (a) and yeast (b) were grown in chemostat to steady state and then switched to different medium. Main figures show protein distribution along time; insets show mean and variance throughout the transient. (a) Bacteria were grown to steady state in glucose and then switched to high concentration of lactose. As a result, an overshoot of induction was seen (blue x; broadest distribution) followed by an adaptive response until a steady state in lactose was reached (green triangles). Then the culture was switched again to glucose (last two distributions, black crosses and magenta squares). (b) Yeast cells were grown in chemostat to steady state in galactose (broadest distribution; red circles), then switched to glucose. The tail of the distribution gradually decreased following the switch until a very narrow distribution (red stars) was reached. In both experiments the mean and variance displayed a quadratic relation (insets).Reuse & Permissions