The Min system disassembles FtsZ foci and inhibits polar peptidoglycan remodeling in Bacillus subtilis

Microfluidic in combination with fluorescence microscopy is a powerful approach for quanatitative analysis of bacterial growth. Here we measure parameters of growth and dynamic localization of the cell division initiation protein FtsZ in Bacillus subtilis. Consistent with previous reports, we find that after division FtsZ rings remain at the cell pole and FtsZ ring disassembly coincides with rapid Z-ring accumulation at the midcell. In cells mutated for minD, however, the polar FtsZ rings persist indefinitely, suggesting that the primary function of the Min system is in Z-ring disassembly. The inability to recycle FtsZ monomers in the minD mutant results in maintenance of multiple Z-rings simultaneously, that are restricted by competition for newly synthesized FtsZ. Whereas the parameters of FtsZ dynamics change in the minD mutant, the overall cell cycle remains the same, albeit with elongated cells necessary to accumulate a threshold concentration of FtsZ for promoting medial division. Finally, the minD mutant characteristically produces minicells composed of polar peptidoglycan shown to be inert for remodeling in the wild type. Polar peptidoglycan however, loses its inert character in the minD mutant suggesting that not only is the Min system important for recycling FtsZ but also may have a secondary role in the regulation of peptidoglycan remodeling.