scholarly journals Effects of ciprofloxacin on plasmid DNA supercoiling of Escherichia coli topoisomerase I and gyrase mutants.

1991 ◽  
Vol 35 (1) ◽  
pp. 20-23 ◽  
Author(s):  
V Aleixandre ◽  
G Herrera ◽  
A Urios ◽  
M Blanco
Keyword(s):  
Escherichia Coli ◽  
Plasmid Dna ◽  
Topoisomerase I ◽  
Dna Supercoiling

scholarly journals Plasmid DNA Supercoiling and Gyrase Activity in Escherichia coli Wild-Type and rpoS Stationary-Phase Cells

2003 ◽  
Vol 185 (3) ◽  
pp. 1097-1100 ◽  
Author(s):  
Yazmid Reyes-Domínguez ◽  
Gabriel Contreras-Ferrat ◽  
Jesús Ramírez-Santos ◽  
Jorge Membrillo-Hernández ◽  
M. Carmen Gómez-Eichelmann
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Plasmid Dna ◽  
Bimodal Distribution ◽  
Dna Supercoiling ◽  
Wild Type

ABSTRACT Stationary-phase cells displayed a distribution of relaxed plasmids and had the ability to recover plasmid supercoiling as soon as nutrients became available. Preexisting gyrase molecules in these cells were responsible for this recovery. Stationary-phase rpoS cells showed a bimodal distribution of plasmids and failed to supercoil plasmids after the addition of nutrients, suggesting that rpoS plays a role in the regulation of plasmid topology during the stationary phase.

scholarly journals Topoisomerase I Essentiality, DnaA-independent Chromosomal Replication, and Transcription-Replication Conflict in Escherichia coli

2021 ◽  
Author(s):  
J Krishna Leela ◽  
Nalini Raghunathan ◽  
J Gowrishankar
Keyword(s):  
Escherichia Coli ◽  
Dna Replication ◽  
Topoisomerase I ◽  
Synthetic Lethality ◽  
Life Forms ◽  
Dna Supercoiling ◽  
Loop Formation ◽  
Chromosomal Dna ◽  
E Coli ◽  
Rnase Hi

Topoisomerase I (Topo I) of Escherichia coli , encoded by topA , acts to relax negative supercoils in DNA. Topo I deficiency results in hypernegative supercoiling, formation of transcription-associated RNA-DNA hybrids (R-loops), and DnaA- and oriC -independent constitutive stable DNA replication (cSDR), but some uncertainty persists as to whether topA is essential for viability in E. coli and related enterobacteria. Here we show that several topA alleles, including Δ topA , confer lethality in derivatives of wild-type E. coli strain MG1655. Viability in absence of Topo I was restored with two perturbations, neither of which reversed the hypernegative supercoiling phenotype: (i) in a reduced-genome strain MDS42, or (ii) by an RNA polymerase (RNAP) mutation rpoB*35 that has been reported to alleviate the deleterious consequences of RNAP backtracking and transcription-replication conflicts. Four phenotypes related to cSDR were identified for topA mutants: (i) One of the topA alleles rescued Δ dnaA lethality; (ii) in dnaA + derivatives, Topo I deficiency generated a characteristic copy number peak in the terminus region of the chromosome; (iii) topA was synthetically lethal with rnhA (encoding RNase HI, whose deficiency also confers cSDR); and (iv) topA rnhA synthetic lethality was itself rescued by Δ dnaA . We propose that the terminal lethal consequence of hypernegative DNA supercoiling in E. coli topA mutants is RNAP backtracking during transcription elongation and associated R-loop formation, which in turn lead to transcription-replication conflicts and to cSDR. Importance In all life forms, double helical DNA exists in a topologically supercoiled state. The enzymes DNA gyrase and topoisomerase I act, respectively, to introduce and to relax negative DNA supercoils in Escherichia coli . That gyrase deficiency leads to bacterial death is well established, but the essentiality of topoisomerase I for viability has been less certain. This study confirms that topoisomerase I is essential for E. coli viability, and suggests that in its absence aberrant chromosomal DNA replication and excessive transcription-replication conflicts occur that are responsible for lethality.

scholarly journals Molecular Interaction between Escherichia Coli Topoisomerase I and pBAD/Thio Supercoiled Plasmid DNA

2015 ◽  
Vol 108 (2) ◽  
pp. 398a
Author(s):  
Purushottam Tiwari ◽  
Thirunavukkarasu Annamalai ◽  
Bokun Cheng ◽  
Gagandeep Narula ◽  
Xuewen Wang ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Plasmid Dna ◽  
Molecular Interaction ◽  
Topoisomerase I ◽  
Supercoiled Plasmid

scholarly journals Uncoupling of the Diurnal Growth Program by Artificial Genome Relaxation in Synechocystis sp. PCC 6803

2021 ◽  
Author(s):  
Anna Behle ◽  
Maximilian Dietsch ◽  
Louis Goldschmidt ◽  
Wandana Murugathas ◽  
David Brandt ◽  
...  
Keyword(s):  
Dna Replication ◽  
Plasmid Dna ◽  
Topoisomerase I ◽  
Metabolic Flux ◽  
Dna Supercoiling ◽  
Dark Cycle ◽  
Dark Light ◽  
Wildtype Cell ◽  
Transcription And Replication ◽  
Pcc 6803

In cyanobacteria DNA supercoiling varies over the diurnal light/dark cycle and is integrated with temporal programs of transcription and replication. We manipulated DNA supercoiling in Synechocystis sp. PCC 6803 by CRISPRi-based knock-down of gyrase subunits and overexpression of topoisomerase I, and characterized the phenotypes. Cell division was blocked, most likely due to inhibition of genomic but not plasmid DNA replication. Cell growth continued to 4-5x of the wildtype cell volume, and metabolic flux was redirected towards glycogen in the topoI overexpession strain. Topoisomerase I induction initially lead to down-regulation of GC-rich and up-regulation of AT-rich genes. The response quickly bifurcated and four diurnal co-expression cohorts (dawn, noon, dusk and night) all responded differently, in part with a circadian (≈24 h) pattern. We suggest a model where energy- and gyrase-gated transcription of growth genes at the dark/light transition (dawn) generates DNA supercoiling which then directly facilitates DNA replication and initiates the diurnal transcriptome program.

Sign in / Sign up

Export Citation Format

Share Document