Reconstitution of Bacterial Plasmid Segregation and its Dynamic Pattern Formation

Abstract

The segregation of genetic material prior to cell division is an essential process for all organisms. In order to maintain faithful inheritance of genetic information, chromosome copies must be partitioned to the daughter cells before cell division. The bacterial P1 plasmid in Escherichia coli is a simple yet useful model system to study the mechanism of chromosome segregation in prokaryotes as they encode only three components that are necessary for plasmid partitioning: a parS DNA sequence on the plasmid acting as the partition site and two partition proteins, ParA and ParB. In vivo studies have shown that the dynamics of ParA, an ATPase, is involved in the positioning of the plasmid copies with ParB bound at parS sites prior to cell division, but how these three components work together to drive plasmid segregation remains unanswered [1]. To better understand the mechanism of P1 plasmid partitioning, we have previously characterized ATP-dependent DNA binding process of ParA [2]. In this work, we reconstituted the three-component partition system in a cell-free reaction. We present the spatio-temporal dynamics of the ParA/B/S partition system observed real-time using TIRF microscopy.[1] Gerdes K, Howard M, Szardenings F, Cell. 2010; 141(6): 927-42.[2] Vecchiarelli AG, Han YW, Tan X, Mizuuchi M, Ghirlando R, Biertumpfel C, Funnell BE, Mizuuchi K., Mol. Microbiol. 2010; 78(1): 78-91.