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Competing ParA Structures Space Bacterial Plasmids Equally over the Nucleoid

Low copy number plasmids in bacteria require segregation for stable inheritance through cell division. This is often achieved by a parABC locus, comprising an ATPase ParA, DNA-binding protein ParB and a parC region, encoding ParB-binding sites. These minimal components space plasmids equally over th...

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Autores principales: Ietswaart, Robert, Szardenings, Florian, Gerdes, Kenn, Howard, Martin
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2014
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4270457/
https://www.ncbi.nlm.nih.gov/pubmed/25521716
http://dx.doi.org/10.1371/journal.pcbi.1004009
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author Ietswaart, Robert
Szardenings, Florian
Gerdes, Kenn
Howard, Martin
author_facet Ietswaart, Robert
Szardenings, Florian
Gerdes, Kenn
Howard, Martin
author_sort Ietswaart, Robert
collection PubMed
description Low copy number plasmids in bacteria require segregation for stable inheritance through cell division. This is often achieved by a parABC locus, comprising an ATPase ParA, DNA-binding protein ParB and a parC region, encoding ParB-binding sites. These minimal components space plasmids equally over the nucleoid, yet the underlying mechanism is not understood. Here we investigate a model where ParA-ATP can dynamically associate to the nucleoid and is hydrolyzed by plasmid-associated ParB, thereby creating nucleoid-bound, self-organizing ParA concentration gradients. We show mathematically that differences between competing ParA concentrations on either side of a plasmid can specify regular plasmid positioning. Such positioning can be achieved regardless of the exact mechanism of plasmid movement, including plasmid diffusion with ParA-mediated immobilization or directed plasmid motion induced by ParB/parC-stimulated ParA structure disassembly. However, we find experimentally that parABC from Escherichia coli plasmid pB171 increases plasmid mobility, inconsistent with diffusion/immobilization. Instead our observations favor directed plasmid motion. Our model predicts less oscillatory ParA dynamics than previously believed, a prediction we verify experimentally. We also show that ParA localization and plasmid positioning depend on the underlying nucleoid morphology, indicating that the chromosomal architecture constrains ParA structure formation. Our directed motion model unifies previously contradictory models for plasmid segregation and provides a robust mechanistic basis for self-organized plasmid spacing that may be widely applicable.
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spelling pubmed-42704572014-12-26 Competing ParA Structures Space Bacterial Plasmids Equally over the Nucleoid Ietswaart, Robert Szardenings, Florian Gerdes, Kenn Howard, Martin PLoS Comput Biol Research Article Low copy number plasmids in bacteria require segregation for stable inheritance through cell division. This is often achieved by a parABC locus, comprising an ATPase ParA, DNA-binding protein ParB and a parC region, encoding ParB-binding sites. These minimal components space plasmids equally over the nucleoid, yet the underlying mechanism is not understood. Here we investigate a model where ParA-ATP can dynamically associate to the nucleoid and is hydrolyzed by plasmid-associated ParB, thereby creating nucleoid-bound, self-organizing ParA concentration gradients. We show mathematically that differences between competing ParA concentrations on either side of a plasmid can specify regular plasmid positioning. Such positioning can be achieved regardless of the exact mechanism of plasmid movement, including plasmid diffusion with ParA-mediated immobilization or directed plasmid motion induced by ParB/parC-stimulated ParA structure disassembly. However, we find experimentally that parABC from Escherichia coli plasmid pB171 increases plasmid mobility, inconsistent with diffusion/immobilization. Instead our observations favor directed plasmid motion. Our model predicts less oscillatory ParA dynamics than previously believed, a prediction we verify experimentally. We also show that ParA localization and plasmid positioning depend on the underlying nucleoid morphology, indicating that the chromosomal architecture constrains ParA structure formation. Our directed motion model unifies previously contradictory models for plasmid segregation and provides a robust mechanistic basis for self-organized plasmid spacing that may be widely applicable. Public Library of Science 2014-12-18 /pmc/articles/PMC4270457/ /pubmed/25521716 http://dx.doi.org/10.1371/journal.pcbi.1004009 Text en © 2014 Ietswaart et al http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
spellingShingle Research Article
Ietswaart, Robert
Szardenings, Florian
Gerdes, Kenn
Howard, Martin
Competing ParA Structures Space Bacterial Plasmids Equally over the Nucleoid
title Competing ParA Structures Space Bacterial Plasmids Equally over the Nucleoid
title_full Competing ParA Structures Space Bacterial Plasmids Equally over the Nucleoid
title_fullStr Competing ParA Structures Space Bacterial Plasmids Equally over the Nucleoid
title_full_unstemmed Competing ParA Structures Space Bacterial Plasmids Equally over the Nucleoid
title_short Competing ParA Structures Space Bacterial Plasmids Equally over the Nucleoid
title_sort competing para structures space bacterial plasmids equally over the nucleoid
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4270457/
https://www.ncbi.nlm.nih.gov/pubmed/25521716
http://dx.doi.org/10.1371/journal.pcbi.1004009
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