English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Background  In low-copy-number plasmids, the partitioning loci ( par ) act to ensure proper plasmid segregation and copy number maintenance in the daughter cells. In many bacterial species,  par  gene homologues are encoded on the chromosome, but their function is much less understood. In the two-replicon, polyploid genome of the hyperthermophilic bacterium  Thermus thermophilus , both the chromosome and the megaplasmid encode  par  gene homologues ( parABc  and  parABm , respectively). The mode of partitioning of the two replicons and the role of the two Par systems in the replication, segregation and maintenance of the genome copies are completely unknown in this organism.    Results  We generated a series of chromosomal and megaplasmid  par  mutants and sGFP reporter strains and analyzed them with respect to DNA segregation defects, genome copy number and replication origin localization. We show that the two ParB proteins specifically bind their cognate centromere-like sequences  parS , and that both ParB- parS  complexes localize at the cell poles. Deletion of the chromosomal  parAB  genes did not apparently affect the cell growth, the frequency of cells with aberrant nucleoids, or the chromosome and megaplasmid replication. In contrast, deletion of the megaplasmid  parAB  operon or of the  parB  gene was not possible, indicating essentiality of the megaplasmid-encoded Par system. A mutant expressing lower amounts of ParABm showed growth defects, a high frequency of cells with irregular nucleoids and a loss of a large portion of the megaplasmid. The truncated megaplasmid could not be partitioned appropriately, as interlinked megaplasmid molecules (catenenes) could be detected, and the ParBm- parSm  complexes in this mutant lost their polar localization.    Conclusions  We show that in  T. thermophilus  the chromosomal  par  locus is not required for either the chromosomal or megaplasmid bulk DNA replication and segregation. In contrast, the megaplasmid Par system of  T. thermophilus  is needed for the proper replication and segregation of the megaplasmid, and is essential for its maintenance. The two Par sets in  T. thermophilus  appear to function in a replicon-specific manner. To our knowledge, this is the first analysis of Par systems in a polyploid bacterium.    Electronic supplementary material  The online version of this article (doi:10.1186/s12864-015-1523-3) contains supplementary material, which is available to authorized users.

Characterization of chromosomal and megaplasmid partitioning loci in Thermus thermophilus HB27