Figure 3. Factors contributing to spatial correlations in colicin Ib expression dynamics.

A) Shared lineage history leads to similarity in Colicin Ib protein levels (left) and promoter activity (right). The phenotypic difference between a focal cell and an equidistant cell (δ_ED) is significantly larger than the phenotypic difference between a focal cell and its closest relative (δ_CR), i.e. 〈δ_ED/δ_CR〉 > 1. B) Spatial proximity leads to similarity in Colicin Ib levels but not in promoter activity. For Colicin Ib levels, the phenotypic difference between a focal cell and an equally-related cell (δ_ED) is significantly larger than the phenotypic difference between the focal cell and one of its neighbors (δ_NB), i.e. 〈δ_ER/δ_NB〉 > 1. C) Local spatial effects do not contribute to spatial correlations in Colicin Ib levels or promoter activity. Local spatial effects were calculated using the residuals of a linear regression of a cell’s phenotype to the distance of a cell to the colony edge. The difference in residuals between a focal cell and an equally-related cell (δ_ER|_resid) is not significantly different from the difference in residuals between the focal cell and one of its neighbors δ_NB|_resid),i.e. δ_ER/δ_NB|_reside ≈ 1. D) Global spatial effects contribute to spatial correlations in Colicin Ib levels. Global spatial effects were calculated as the difference between the total effects of spatial proximity (panel B) and the local spatial effects (panel C). A-D) Each point corresponds to a microcolony with 117-138 (mean=128) cells; points are horizontally offset. Thick horizontal lines indicate mean, thin lines 95% confidence intervals. Dashed lines indicate the expected value under the null-hypothesis. Null hypothesis rejected with: *p<0.05, **p<0.01, ***p<0.001, t-test, n=9. The statistics are robust to the choice of the equally-related cell (Figure S4A), the size of the colony being analyzed (Figure S4B), and differences in the processing of fluorescent images (Figure S4C). Full distributions are shown in Figure S5. See also Figure S4-8