Additional file 6: Figure S6. of Asymmetric cellular memory in bacteria exposed to antibiotics

It has been reported that the blaA (CC2139) gene is a major contributor to ampicillin resistance in C. crescentus [22]. We measured expression of blaA using a transcriptional reporter (see Methods). GFP (green fluorescent protein) intensity, a proxy for transcriptional activity of blaA, was measured before (t1) and after (t2) the warning event (0 or 10 µg/mL ampicillin for 2 h). After background correction the intensity level at t2 was subtracted from the intensity level at t1. (A) The mean of the differences is represented by the bars (error bars denote standard errors of the mean). For both conditions the intensity levels at t1 was compared to the intensity levels at t2 using a paired t-test statistic (N = 117 and 119 for 0 and 10 µg/mL ampicillin exposure). When cells were exposed to 10 µg/mL ampicillin for 2 h (yellow), the increase of the measured GFP intensity was significant (p < 0.01), while for the unwarned cells (green) no significant changes were observed (p = 0.3). (B) Numbers of surviving and dead cells are reported for small intervals of GFP intensity values (20 bins from -1.5 to 2.5 with size 0.2). No statistically significant association of GFP levels with survival after stress (logistic regression p = 0.68) could be established. (PNG 272 kb)