Figure 4

Fluorescence microscopy of E. coli C41(DE3) pLysS cells expressing L. paracasei YafQ and DinJ stained with ThT and imaged before (left) and after (right) 20 hours incubation. (a) Cells producing YafQ_pa4366 toxin, (b) cells producing YafQ_pa4366 toxin and DinJ_pa4366 antitoxin, (c) cells producing YafQ_pa2333 non-toxic protein. (d) Box-plot of the cell average fluorescence intensity relative to the six sets of images: green boxes refer to the conditions in (a) orange boxes refer to the conditions in (b) blue boxes refer to the conditions in (c). The boundaries of the box plot indicate the 25th and 75th percentile of the distribution, the horizontal line within the box represents the median and the error bars show the 10th and 90th percentile of the distribution. The total number of cells in each box-plot from left to right is: 1757, 1057, 1929, 1902, 1596, 1641. Each pair of box-plots was subjected to the Mann–Whitney U test to verify the statistical significance of the difference between the two distributions. Fold changes (FC) and probability (P) values are: FC = 0.754 P ≤ 0.001 for YafQ_pa4366 (green boxes); FC = 0.960 P = 0.011 for YafQ_pa4366/DinJ_pa4366 (orange boxes); FC = 1.134 P ≤ 0.001 for YafQ_pa2333 (blue boxes).