A Defined Terminal Region of the E. coli Chromosome Shows Late Segregation and High FtsK Activity

Background: The FtsK DNA-translocase controls the last steps of chromosome segregation in E. coli. It translocates sister chromosomes using the KOPS DNA motifs to orient its activity, and controls the resolution of dimeric forms of sister chromosomes by XerCD-mediated recombination at the dif site and their decatenation by TopoIV. Methodology: We have used XerCD/dif recombination as a genetic trap to probe the interaction of FtsK with loci located in different regions of the chromosome. This assay revealed that the activity of FtsK is restricted to a,400 kb terminal region of the chromosome around the natural position of the dif site. Preferential interaction with this region required the tethering of FtsK to the division septum via its N-terminal domain as well as its translocation activity. However, the KOPSrecognition activity of FtsK was not required. Displacement of replication termination outside the FtsK high activity region had no effect on FtsK activity and deletion of a part of this region was not compensated by its extension to neighbouring regions. By observing the fate of fluorescent-tagged loci of the ter region, we found that segregation of the FtsK high activity region is delayed compared to that of its adjacent regions. Significance: Our results show that a restricted terminal region of the chromosome is specifically dedicated to the last step

FtsK-Dependent Dimer Resolution on Multiple Chromosomes in the Pathogen Vibrio cholerae

Unlike most bacteria, Vibrio cholerae harbors two distinct, nonhomologous circular chromosomes (chromosome I and II). Many features of chromosome II are plasmid-like, which raised questions concerning its chromosomal nature. Plasmid replication and segregation are generally not coordinated with the bacterial cell cycle, further calling into question the mechanisms ensuring the synchronous management of chromosome I and II. Maintenance of circular replicons requires the resolution of dimers created by homologous recombination events. In Escherichia coli, chromosome dimers are resolved by the addition of a crossover at a specific site, dif, by two tyrosine recombinases, XerC and XerD. The process is coordinated with cell division through the activity of a DNA translocase, FtsK. Many E. coli plasmids also use XerCD for dimer resolution. However, the process is FtsK-independent. The two chromosomes of the V. cholerae N16961 strain carry divergent dimer resolution sites, dif1 and dif2. Here, we show that V. cholerae FtsK controls the addition of a crossover at dif1 and dif2 by a common pair of Xer recombinases. In addition, we show that specific DNA motifs dictate its orientation of translocation, the distribution of these motifs on chromosome I and chromosome II supporting the idea that FtsK translocation serves to bring together the resolution sites carried by a dimer at the time of cell division. Taken together, these results suggest that the same FtsK-dependent mechanism coordinates dimer resolution with cell division for each of the two V. cholerae chromosomes. Chromosome II dimer resolution thus stands as a bona fide chromosomal process

Asymmetry of Chromosome Replichores Renders the DNA Translocase Activity of FtsK Essential for Cell Division and Cell Shape Maintenance in Escherichia coli

Bacterial chromosomes are organised as two replichores of opposite polarity that coincide with the replication arms from the ori to the ter region. Here, we investigated the effects of asymmetry in replichore organisation in Escherichia coli. We show that large chromosome inversions from the terminal junction of the replichores disturb the ongoing post-replicative events, resulting in inhibition of both cell division and cell elongation. This is accompanied by alterations of the segregation pattern of loci located at the inversion endpoints, particularly of the new replichore junction. None of these defects is suppressed by restoration of termination of replication opposite oriC, indicating that they are more likely due to the asymmetry of replichore polarity than to asymmetric replication. Strikingly, DNA translocation by FtsK, which processes the terminal junction of the replichores during cell division, becomes essential in inversion-carrying strains. Inactivation of the FtsK translocation activity leads to aberrant cell morphology, strongly suggesting that it controls membrane synthesis at the division septum. Our results reveal that FtsK mediates a reciprocal control between processing of the replichore polarity junction and cell division

The Transcriptome of the Nosocomial Pathogen Enterococcus faecalis V583 Reveals Adaptive Responses to Growth in Blood

gains access to the bloodstream and establishes a persistent infection is not well understood.. infections

Physico-chemical properties and microbiological activity of some organic substrates used for growing plants and for suppressive purposes

International audienceSan

Interplay between recombination, cell division and chromosome structure during chromosome dimer resolution in Escherichia coli.

Chromosome dimers form in bacteria by recombination between circular chromosomes. Resolution of dimers is a highly integrated process involving recombination between dif sites catalysed by the XerCD recombinase, cell division and the integrity of the division septum-associated FtsK protein and the presence of dif inside a restricted region of the chromosome terminus, the dif activity zone (DAZ). We analyse here how these phenomena collaborate. We show that (i) both inter- and intrachromosomal recombination between dif sites are activated by their presence inside the DAZ; (ii) the DAZ-specific activation only occurs in conditions supporting the formation of chromosome dimers; (iii) overexpression of FtsK leads to a general increase in dif recombination irrespective of dif location; (iv) overexpression of FtsK does not improve the ability of dif sites inserted outside the DAZ to resolve chromosome dimers. Our results suggest that the formation of an active XerCD-FtsK-dif complex is restricted to when a dimer is present, the features of chromosome organization that determine the DAZ playing a central role in this control

Synthesis and “in vitro” characterization of melt derived 47S CaO-P2O5-SiO2-NaO bioactive glass

Ceramics - Silikaty, 2008, 3, 121 – 12

2D distribution of Pseudomonas fluorescens activities at the soil-root interface of sunflower grown on vineyard soils: Effects on copper uptake

International audiencePseudomonas fluorescens is a siderophore producing bacteria that is expected to alter the mobility and bioavailability of Cu in vineyard soils due to its ability to produce pyoverdine under iron deficiency. In this study, we monitored the effect of this bacterial species, particularly the production of siderophore, on the mobility and bioavailability of copper (Cu) and other elements using a spatialized approach. Two vineyard soils cultivated with sunflower, one non-carbonated (N-Carb) and one carbonated (Carb), were bioaugmented with P. fluorescens or not. 2D mapping using diffusive equilibration in thin films (DET) and diffusive gradient in thin films (DGT) was performed on day 15 after germination. At the end of the experiment, elements concentrations were measured in the plants and in the soil extracts (CaCl2 0.01 M). The results showed that the mobility of Cu and other elements (Fe, Al, Mn, Zn, N and P) was enhanced in both soils when bioaugmented. The chemistry of DET and DGT provided insights into the processes behind mobility, such as the presence and distribution of free metallophore spots (2–3.5 μM), interpreted as pyoverdine, which played a non-negligible role in Cu, Fe, Al mobilization and to a lesser extent in that of Mn, whereas pH played a limited role. DGT imaging showed that, depending on the speciation of metals in the soil solution, the increase in mobility measured by DET did not always increase bioavailability. Nevertheless, the concentration of copper in the aerial part of sunflower cultivated on the bioaugmented carbonated soil increased by 30% and copper content by 200%. These results identify bioaugmentation with P. fluorescens as a potential way to increase Cu phytoextraction, especially in carbonated soil, mainly because of its effect on plant growth but also on Cu bioavailability at the soil-plant interface. © 2021 Elsevier Lt