A cell length‐dependent transition in MinD‐dynamics promotes a switch in division‐site placement and preservation of proliferating elongated Vibrio parahaemolyticus swarmer cells

Abstract

Vibrio parahaemolyticus exists as swimmer and swarmer cells, specialized for growth in liquid and on solid environments respectively. Swarmer cells are characteristically highly elongated due to an inhibition of cell division, but still need to divide in order to proliferate and expand the colony. It is unknown how long swarmer cells divide without diminishing the population of long cells required for swarming behavior. Here we show that swarmer cells divide but the placement of the division site is cell length-dependent; short swarmers divide at mid-cell, while long swarmers switch to a specific non-mid-cell placement of the division site. Transition to non-mid-cell positioning of the Z-ring is promoted by a cell length-dependent switch in the localization-dynamics of the division regulator MinD from a pole-to-pole oscillation in short swarmers to a multi-node standing-wave oscillation in long swarmers. Regulation of FtsZ levels restricts the number of divisions to one and SlmA ensures sufficient free FtsZ to sustain Z-ring formation by preventing sequestration of FtsZ into division deficient clusters. By limiting the number of division-events to one per cell at a specific non-mid-cell position, V. parahaemolyticus promotes the preservation of long swarmer cells and permits swarmer cell division without the need for dedifferentiation.

In long bacterial cells, the Min system can act off‐center

“…Although this is still likely true for cells smaller than the wavelength of the Min system, the work by Muraleedharan et al . show how multi‐nodal Min dynamics that emerge in elongated cells can be used to align non‐mid‐cell divisions (Muraleedharan et al ., ).…”

“…Muraleedharan et al . shows that swarmer cells indeed divide, but positioning of the cell division machinery is dependent upon cell length – small cells (less than 10 microns in length) divide at mid‐cell, while long cells (greater than 10 microns) transition to an off‐center division site (Muraleedharan et al, ).…”

“…The authors find that a switch to non‐mid‐cell division is mediated by a cell‐length‐dependent transition in the number and position of nodes generated by the Min system (Muraleedharan et al ., ). Consistent with the previously studied Min systems of E. coli, B. subtilus and S. elongatus , both swimmer‐ and swarmer‐cells less than 10 microns in length support a single node where MinD/MinC concentrations are minimum at mid‐cell (Fig.…”

“…Two nodes provide the cell with two potential sites for a functional Z ring, however, the authors find that only one of these quarter positions are selected for Z ring formation and cell division (Muraleedharan et al ., ). In very long swarmer cells, Min dynamics transition from 2 to 4 nodes for cells between 20 and 30 microns in length, and then from 4 to 6 nodes for cells 30–40 microns in length.…”

“…This has also been shown for SlmA of V. Cholerae (Galli et al, ). In the absence of SlmA in V. parahaemolyticus , the authors found that FtsZ forms division‐deficient clusters along the cell length rather than a single, division‐competent Z ring (Muraleedharan et al ., ). Therefore, FtsZ is inhibited from accumulating along the cell length by SlmA, which is bound to the multiple copies of nucleoids occupying the entire length of the cell.…”