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Jennifer Herricks

Advisor: William Margolin, Ph.D.

Cytokinesis is a fundamental process that is essential for bacterial proliferation. The cytokinetic machinery in bacteria is termed the “divisome”. The divisome is a complex of proteins that forms a ring at midcell over dividing nucleoids. In order for daughter cells to form, the divisome must constrict. As constriction occurs, two new cell poles are formed, one for each daughter cell. The first step in divisome formation is the assembly of FtsZ into a Z ring. The work presented in this dissertation focuses on two proteins that regulate the Z ring: MinD, which is a part of the Min system and important for positioning of the divisome; and FtsA, involved in early and late stages of divisome formation with a speculated role in regulating its constriction and disassembly. In E. coli the Min proteins oscillate from pole-to-pole to prevent Z ring formation at the cell poles. I found that MinD oscillation becomes irregular as cell length increases, and that it starts to pause frequently at each side of the developing septum. Eventually this irregular pattern switches to a doubled, regular pattern that is maintained in newly born daughter cells. I suggest this may be the mechanism by which Min proteins are equally distributed in daughter cells. My studies of FtsA show that ATP binding is important for its function in vivo, affecting its ability to interact with FtsZ and possibly with itself and other division proteins. I also show for the first time that E. coli FtsA can hydrolyze ATP.

Research Info

Regulators of Bacterial Cell Division: Investigations of Min Oscillation and FtsA Activity