The bacterial segrosome: a dynamic nucleoprotein machine for DNA trafficking and segregation

Abstract

The genomes of unicellular and multicellular organisms must be partitioned equitably in coordination with cytokinesis to ensure faithful transmission of duplicated genetic material to daughter cells. Bacteria use sophisticated molecular mechanisms to guarantee accurate segregation of both plasmids and chromosomes at cell division. Plasmid segregation is most commonly mediated by a Walker-type ATPase and one of many DNA-binding proteins that assemble on a cis-acting centromere to form a nucleoprotein complex (the segrosome) that mediates intracellular plasmid transport. Bacterial chromosome segregation involves a multipartite strategy in which several discrete protein complexes potentially participate. Shedding light on the basis of genome segregation in bacteria could indicate new strategies aimed at combating pathogenic and antibiotic-resistant bacteria.

Conjugative plasmids: vessels of the communal gene pool

“…Low copy number conjugative plasmids, however, have to rely on active mechanisms, usually a nucleoprotein complex (the segrosome), which ensures that plasmids are actively moved into position prior to cell division in a manner analogous to eukaryotic mitotic division. This mechanism is, in the majority of observed cases, encoded on par loci consisting of two genes, often given the generic parA and parB denomination, that encode trans-acting proteins and a centromere-like cis-region sometimes named the parS site (Tolmasky et al 2000;Hayes & Barilla 2006). In most cases, one gene (parA) encodes an ATPase, which provides the energy required for the intracellular movement and distribution of plasmids, which binds to a DNA-binding protein (encoded by parB) that, in turn, binds to the plasmid centromere region.…”

Two novel conjugative plasmids from a single strain of Sulfolobus

“…Surprisingly, a homologue of ParA/SopA appears not to be encoded by pSOG1. In bacteria, plasmid partitioning during cell division proceeds via the so-called segrosome, a protein complex at least consisting of ParA and ParB, which are encoded by the plasmid-borne par locus (Gerdes et al, 2000; reviewed by Hayes & Barilla, 2006). ParA is a membrane-associated…”

Characterization of the mycobacterial chromosome segregation protein ParB and identification of its target in Mycobacterium smegmatis

“…Bacterial chromosome segregation has been recently found to be an active and complex process closely coupled with replication (see Bartosik & Jagura-Burdzy, 2005;Errington et al, 2005;Hayes & Barilla, 2006;Leonard et al, 2005 for reviews). In bacteria studied to date, the newly synthesized origin (oriC) regions undergo a symmetric or asymmetric segregation process; two copies of the duplicated oriC regions migrate from the cell centre toward opposite cell poles, i.e.…”

“…Knowledge regarding the steps of the mycobacterial cell cycle (replication, chromosome segregation and cell division) seems to be critical for understanding the mechanisms that are responsible for the transition from an active to a non-replicative persistent state (and vice versa) of pathogenic mycobacteria, particularly M. tuberculosis. While initiation of chromosome replication Qin et al, 1999;Rajagopalan et al, 1995;Zawilak et al, 2004) and cell division (FtsZ ring formation) (Chauhan et al, 2006; Dziadek et al, 2002Dziadek et al, , 2003Huang et al, 2007;Rajagopalan et al, 2005) are relatively well studied in mycobacteria, nothing is known about the segregation of chromosomes in these bacteria.Bacterial chromosome segregation has been recently found to be an active and complex process closely coupled with replication (see Bartosik & Jagura-Burdzy, 2005;Errington et al, 2005;Hayes & Barilla, 2006; Leonard et al, 2005 for reviews). In bacteria studied to date, the newly synthesized origin (oriC) regions undergo a symmetric or asymmetric segregation process; two copies of the duplicated oriC regions migrate from the cell centre toward opposite cell poles, i.e.…”