The Agrobacterium tumefaciens min system contributes to the regulation of cell division

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] In A. tumefaciens, the essential FtsZ protein is located at the growth pole before shifting to the mid-cell right before division. Recruitment of FtsZ to mid-cell is required for septum formation and subsequent cell separation during cell division. For this research, we have conducted a systematic characterization of the Min system in A. tumefaciens to better understand the regulation of FtsZ ring placement. Remarkably, the Min system is not required for cell survival. Yet we find that the minE and minCDE deletion causes the most pronounced phenotype, presumably due to misplacement of the FtsZ rings. When minCDE is deleted we observe that many cells grow normally; however some cells become elongated and have multiple sites of constriction and other cells become branched. Branching can be caused by uncontrolled growth or failure to complete cytokinesis during cell division. Additionally we find that the minE deletion causes a broad range of cell lengths from mini cells to elongated cells. We observe that asymmetric placement of FtsZ rings leads to cell division resulting in daughter cells of different cell lengths. Remarkably, small cells contain DNA; however, chromosome segregation is impaired in the minE deletion strain. Taken together, our data suggest that the Min system contributes to the proper regulation of FtsZ placement and subsequent cell division.