Figure 3
Effect of over-expression of the putative toxin proteins RelE1sca and RelE2sca on the growth of E. coli MGJ5987 (MG1655 ∆relBE mutant).
E. coli MGJ5987 cells transformed with individual plasmids were grown in LB medium until the OD600 reached 0.2: (a) control plasmid (pBAD/myc-hisA), (b) plasmid carrying relE1sca (pBAD-relE1sca), (c) plasmid carrying relE2sca (pBAD-relE2sca) and (d) plasmid carrying the intact relBE2sca operon (pBAD-relBE2sca). Then, at time zero, 0.2% glucose (the hollow square) was added into one-half of each culture and 0.2% L-arabinose (the solid square) was added into the other half. Cell growth was monitored by measuring the OD600 every 30 minutes. The means and standard deviation of three different experiments are shown. For statistical analysis, two-way analysis of variance with Bonferroni post-tests were used to obtain P values for each time point: *P < 0.05; **P < 0.01; ***P < 0.001. 3 μl of serial dilutions of different cultures which were collected after induction by glucose or arabinose for 1 hour were spread onto the LA plate and incubated at 37 °C for 12 hours.
