We used two different approaches to do so. First, we computed the coefficient of variation (CV, the ratio between click here the see more standard deviation and the mean) for each measurement of GFP fluorescence. As control, we used the reporter for rpsM, which encodes the ribosomal protein S13, previously shown to exhibit a low degree of variation in the expression between clonal cells [31]. The ptsG reporter showed higher CVs than the mglB reporter in all glucose-feed environments (Table 2, Additional file 1: File S1), and also higher CVs than the PrpsM-gfp control (Figure 1, Table 2). However, CVs alone are not a reliable indicator for the level of heterogeneity in gene expression, since it has been previously demonstrated that
CVs are dependent on the mean expression level [31]. This relationship also manifests in our dataset in all tested growth conditions (presented in the next section of Results and Discussion). Table 1 Values for mean log expression of measured reporter strains Mean log expression Experimental conditions ptsG mglB rpsM acs Chemostat, D = 0.15 h-1; 0.56 mM Glc 1.94 ± 0.02 2.78 ± 0.01 2.84 ± 0.03 2.18 ± 0.02 Batch; 0.56 mM Glc 2.05 ± 0.02 2.19 ± 0.01 3.14 ± 0.01 1.90 ± 0.02 Chemostat, D = 0.3 h-1; 0.56 mM Glc 2.11 ± 0.06 2.75 ± 0.02 2.78 ± 0.09
2.12 ± 0.01 Chemostat, D = 0.15 h-1; 5.6 mM Glc 2.18 ± 0.03 2.75 ± 0.03 2.97 ± 0.01 1.93 ± 0.02 Batch; 5.6 mM Glc 1.94 ± 0.02 2.25 ± 0.04 3.25 ± 0.00 1.50 ± 0.06 Chemostat, D = 0.15 h-1; 0.56 mM Sapitinib nmr Ac 1.36 ± 0.04 2.83 ± 0.05 2.65 ± 0.02 2.24 ± 0.00 Batch; 0.56 mM Ac 1.44 ± 0.03 2.80 ± 0.02 2.81 ± 0.03 1.97 ± 0.16 Chemostat, D = 0.15 h-1; 5.6 mM Ac 1.57 ± 0.02 2.87 ± 0.02 2.81 ± 0.03 2.18 ± 0.02 Batch; 5.6 mM Ac 1.19 ± 0.00 2.85 ± 0.02 2.82 ± 0.03 1.91 ± 0.01 Chemostat, D = 0.15 h-1; 2.8 mM Glc, 2.8 mM Ac 2.02 ± 0.02 2.78 ± 0.08 2.78 ± 0.01 2.04 ± 0.00 Batch; 2.8 mM Glc, 2.8 mM Ac 1.96 ± 0.01 2.23 ± 0.02
3.20 ± 0.04 1.66 ± 0.01 Chemostat, D = 0.15 h-1; 0.28 mM Glc, Cepharanthine 0.28 mM Ac 1.71 ± 0.04 2.81 ± 0.02 2.74 ± 0.02 2.06 ± 0.02 Batch; 0.28 mM Glc, 0.28 mM Ac 1.98 ± 0.002 2.37 ± 0.02 3.11 ± 0.02 1.85 ± 0.01 The values are represented as mean of the replicates ± standard error of the mean. Table 2 Values for CV of log expression of measured reporter strains CV of log expression Experimental conditions ptsG mglB rpsM acs Chemostat, D = 0.15 h-1; 0.56 mM Glc 0.21 ± 0.02 0.17 ± 0.01 0.13 ± 0.02 0.14 ± 0.02 Batch; 0.56 mM Glc 0.12 ± 0.01 0.08 ± 0.00 0.06 ± 0.00 0.14 ± 0.00 Chemostat, D = 0.3 h-1; 0.56 mM Glc 0.25 ± 0.01 0.15 ± 0.01 0.19 ± 0.07 0.11 ± 0.01 Chemostat, D = 0.15 h-1; 5.6 mM Glc 0.15 ± 0.01 0.11 ± 0.01 0.08 ± 0.01 0.15 ± 0.01 Batch; 5.6 mM Glc 0.10 ± 0.01 0.10 ± 0.01 0.07 ± 0.01 0.24 ± 0.02 Chemostat, D = 0.15 h-1; 0.56 mM Ac 0.46 ± 0.03 0.22 ± 0.03 0.25 ± 0.01 0.22 ± 0.00 Batch; 0.56 mM Ac 0.47 ± 0.02 0.22 ± 0.01 0.20 ± 0.03 0.38 ± 0.10 Chemostat, D = 0.15 h-1; 5.6 mM Ac 0.28 ± 0.01 0.17 ± 0.01 0.21 ± 0.02 0.19 ± 0.02 Batch; 5.6 mM Ac 0.64 ± 0.00 0.