RT Journal Article SR Electronic T1 Noc corrals migration of FtsZ protofilaments during cytokinesis in Bacillus subtilis JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.08.27.271361 DO 10.1101/2020.08.27.271361 A1 Yuanchen Yu A1 Jinsheng Zhou A1 Fredy Gueiros-Filho A1 Daniel B. Kearns A1 Stephen C. Jacobson YR 2020 UL http://biorxiv.org/content/early/2020/08/31/2020.08.27.271361.abstract AB Bacteria that divide by binary fission form FtsZ rings at the geometric midpoint of the cell between the bulk of the replicated nucleoids. In B. subtilis, the DNA- and membrane-binding Noc protein is thought to mediate nucleoid occlusion to prevent FtsZ rings from forming over the chromosome. To explore the role of Noc, we used time-lapse fluorescence microscopy to monitor FtsZ and the nucleoid of cells growing in microfluidic channels. Our data show that Noc does not prevent FtsZ formation over the chromosome or control cell division site selection. Instead, Noc inhibits migration of FtsZ protofilaments from one FtsZ structure to the next. Moreover, we show that FtsZ protofilaments travel due to a local reduction in ZapA association, and the Noc mutant phenotype can be suppressed by ZapA overexpression. Thus, Noc maintains a high local concentration of FtsZ to stabilize FtsZ rings during cytokinesis.IMPORTANCE In bacteria, a condensed structure of FtsZ (Z-ring) recruits cell division machinery, and Z-ring formation is inhibited over the chromosome by a poorly understood phenomenon called nucleoid occlusion. In B. subtilis, nucleoid occlusion has been reported to be mediated by the DNA-membrane bridging protein, Noc. Using time-lapse fluorescence microscopy of cells growing in microchannels, we show that Noc neither protects the chromosome from proximal Z-ring formation nor determines the future site of cell division. Rather, Noc plays a corralling role by preventing protofilaments from leaving a Z-ring undergoing cytokinesis and traveling over the nucleoid.