A Carbocyclic Curcumin Inhibits Proliferation of Gram-Positive Bacteria by Targeting FtsZ

Inhibition of FtsZ assembly has been found to stall bacterial cell division. Here, we report the identification of a potent carbocyclic curcumin analogue (<b>2d</b>) that inhibits <i>Bacillus subtilis</i> 168 cell proliferation by targeting the assembly of FtsZ. <b>2d</b> also showed potent inhibitory activity (minimum inhibitory concentrations of 2–4 mg/L) against several clinically important species of Gram-positive bacteria, including methicillin-resistant <i>Staphylococcus aureus</i>. In addition, <b>2d</b> displayed a significantly reduced inhibitory effect on human cervical cancer cells in comparison to its effect on bacterial cells. Using live cell imaging of GFP-FtsZ by confocal microscopy, <b>2d</b> was found to rapidly perturb the cytokinetic FtsZ rings in <i>Bacillus subtilis</i> cells. The immunofluorescence imaging of FtsZ also showed that <b>2d</b> destroyed the Z-ring in bacteria within 5 min. Prolonged treatment with <b>2d</b> produced filamentous bacteria, but <b>2d</b> had no detectable effect either on the nucleoids or on the membrane potential of bacteria. <b>2d</b> inhibited FtsZ assembly <i>in vitro</i>, whereas it had minimal effects on tubulin assembly. Interestingly, <b>2d</b> strongly enhanced the GTPase activity of FtsZ and reduced the GTPase activity of tubulin. Furthermore, <b>2d</b> bound to purified FtsZ with a dissociation constant of 4.0 ± 1.1 μM, and the binding of <b>2d</b> altered the secondary structures of FtsZ. The results together suggested that the non-natural curcumin analogue <b>2d</b> possesses powerful antibacterial activity against important pathogenic bacteria, and the evidence indicates that <b>2d</b> inhibits bacterial proliferation by targeting FtsZ