Figure 1.
Chemical structures of antibacterial compounds used in this study.
Table 1.
Plasmids used in this study.
Table 2.
Structure of PNA used in this study.
Table 3.
Escherichia coli strains used in this study.
Figure 2.
Bacterial SOS response in the presence of berberine.
The doses of each compound were chosen as indicated percentage of the MIC (4 mM, 15 nM and 400 nM for berberine, mitomycin C and triclosan, respectively). Mitomycin C and triclosan were included as positive and negative controls for SOS induction. The Relative Fluorescence Units (RFUs) indicate the level of SOS reporter expression in the SOS-negative E. coli strain SS996.
Figure 3.
Effect of berberine on E. coli morphology.
Bacteria (wild-type and the SOS-negative strain) were either untreated or treated with 1.5 mM berberine. Scale bars are 10 µm.
Figure 4.
Z-ring formation and cell morphology in berberine-treated E. coli.
Representative cells untreated and treated with 3 mM berberine; FtsZ was tagged with YFP and bacterial DNA was visualised through staining with DAPI. Scale bars are 10 µm.
Figure 5.
Effect of expressed antisense RNA-mediated ftsZ silencing on E. coli growth and susceptibility to berberine.
(A) Growth curves for the SOS-negative strains carrying the control and anti-ftsZ plasmids. Antisense expression was induced by a range of IPTG concentrations (0–70 µM) and cells were treated with the indicated concentrations of berberine. (B) Regression analysis of IPTG concentration and the MIC of berberine in both strains.
Figure 6.
Effect of PNA-mediated ftsZ silencing on cell growth and susceptibility to berberine in E. coli K-12 strain.
(A) Typical growth curves; cells were grown in the presence one of two different PNAs: Ec326 (anti-ftsZ) or Ec107 (anti-fabI, negative control) in a range of concentrations (0–2 µM) and treated with the indicated concentrations of berberine. (B) Regression analysis of PNA concentration and the MIC of berberine.
Figure 7.
Over-expression of ftsZ and its effect on E. coli growth in the presence and absence of berberine.
Bacteria (E. coli DH5α carrying plasmid pBAD-ftsZ) were induced using a concentration range of L-arabinose (0–0.01%) to allow over-expression of the FtsZ protein and grown in the absence or presence of berberine. The growth rate in the absence of L-arabinose or berberine was set as 1. As a control, E. coli DH5α without the plasmid was treated with berberine in the same range of L-arabinose concentrations.