Mechanistic insight into the effect of BT-benzo-29 on the Z-ring in Bacillus subtilis

The assembly and disassembly of FtsZ play an essential role in bacterial cell division. Using single-cell imaging, we report that short exposure to BT-benzo-29 inhibits Z-ring formation in live Bacillus subtilis cells. Fluorescence recovery after photobleaching of the Z-ring in live bacteria demonstrated that BT-benzo-29 strongly suppressed the assembly dynamics of FtsZ in the Z-ring. Furthermore, B. subtilis cells expressing V275A-FtsZ resisted the antibacterial activity of BT-benzo-29 providing evidence that BT-benzo-29 inhibits bacterial proliferation by targeting FtsZ. In addition, a brief (8 min) exposure of BT-benzo-29 destroyed the Z-ring without perturbing the localization of a late cell division protein, DivIVA, the nucleoid segregation, and membrane permeability. BT-benzo-29, when used in combination with vancomycin and polymyxin B (PMB), produced a much stronger inhibitory effect on Bacillus subtilis and Escherichia coli cells, respectively. The combination index of BT-benzo-29 with vancomycin and PMB was determined to be <1, suggesting that BT-benzo-29 exhibits synergistic inhibitory effects on bacterial proliferation when used along with these antibiotics.