Plasmids used in this study.

<p>*antisense target locations are indicated relative to the start codon.</p

Over-expression of <i>ftsZ</i> and its effect on <i>E. coli</i> growth in the presence and absence of berberine.

<p>Bacteria (<i>E. coli</i> 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, <i>E. coli</i> DH5α without the plasmid was treated with berberine in the same range of L-arabinose concentrations.</p

Z-ring formation and cell morphology in berberine-treated <i>E. coli</i>.

<p>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.</p

Bacterial SOS response in the presence of berberine.

<p>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 <i>E. coli</i> strain SS996.</p

Effect of berberine on <i>E. coli</i> morphology.

<p>Bacteria (wild-type and the SOS-negative strain) were either untreated or treated with 1.5 mM berberine. Scale bars are 10 µm.</p

Structure of PNA used in this study.

<p>*antisense target locations are indicated relative to the start codon.</p

<i>Escherichia coli</i> strains used in this study.

<p><i>Escherichia coli</i> strains used in this study.</p

Effect of expressed antisense RNA-mediated <i>ftsZ</i> silencing on <i>E. coli</i> growth and susceptibility to berberine.

<p>(A) Growth curves for the SOS-negative strains carrying the control and anti-<i>ftsZ</i> 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.</p

Effect of PNA-mediated <i>ftsZ</i> silencing on cell growth and susceptibility to berberine in <i>E. coli</i> K-12 strain.

<p>(A) Typical growth curves; cells were grown in the presence one of two different PNAs: Ec326 (anti-<i>ftsZ</i>) or Ec107 (anti-<i>fabI</i>, 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.</p

Chemical structures of antibacterial compounds used in this study.

<p>Chemical structures of antibacterial compounds used in this study.</p