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

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.