Differential Regulation of Horizontally Acquired and Core Genome Genes by the Bacterial Modulator H-NS

Horizontal acquisition of DNA by bacteria dramatically increases genetic diversity and hence successful bacterial colonization of several niches, including the human host. A relevant issue is how this newly acquired DNA interacts and integrates in the regulatory networks of the bacterial cell. The global modulator H-NS targets both core genome and HGT genes and silences gene expression in response to external stimuli such as osmolarity and temperature. Here we provide evidence that H-NS discriminates and differentially modulates core and HGT DNA. As an example of this, plasmid R27-encoded H-NS protein has evolved to selectively silence HGT genes and does not interfere with core genome regulation. In turn, differential regulation of both gene lineages by resident chromosomal H-NS requires a helper protein: the Hha protein. Tight silencing of HGT DNA is accomplished by H-NS-Hha complexes. In contrast, core genes are modulated by H-NS homoligomers. Remarkably, the presence of Hha-like proteins is restricted to the Enterobacteriaceae. In addition, conjugative plasmids encoding H-NS variants have hitherto been isolated only from members of the family. Thus, the H-NS system in enteric bacteria presents unique evolutionary features. The capacity to selectively discriminate between core and HGT DNA may help to maintain horizontally transmitted DNA in silent form and may give these bacteria a competitive advantage in adapting to new environments, including host colonization

Phage Encoded H-NS: A Potential Achilles Heel in the Bacterial Defence System

The relationship between phage and their microbial hosts is difficult to elucidate in complex natural ecosystems. Engineered systems performing enhanced biological phosphorus removal (EBPR), offer stable, lower complexity communities for studying phage-host interactions. Here, metagenomic data from an EBPR reactor dominated by Candidatus Accumulibacter phosphatis (CAP), led to the recovery of three complete and six partial phage genomes. Heat-stable nucleoid structuring (H-NS) protein, a global transcriptional repressor in bacteria, was identified in one of the complete phage genomes (EPV1), and was most similar to a homolog in CAP. We infer that EPV1 is a CAP-specific phage and has the potential to repress up to 6% of host genes based on the presence of putative H-NS binding sites in the CAP genome. These genes include CRISPR associated proteins and a Type III restriction-modification system, which are key host defense mechanisms against phage infection. Further, EPV1 was the only member of the phage community found in an EBPR microbial metagenome collected seven months prior. We propose that EPV1 laterally acquired H-NS from CAP providing it with a means to reduce bacterial defenses, a selective advantage over other phage in the EBPR system. Phage encoded H-NS could constitute a previously unrecognized weapon in the phage-host arms race

Single-molecule study on histone-like nucleoid-structuring protein (H-NS) paralogue in Pseudomonas aeruginosa: MvaU Bears DNA organization mode similarities to MvaT

10.1371/journal.pone.0112246PLoS ONE911e11224

Sultiame pharmacokinetic profile in plasma and erythrocytes after single oral doses: A pilot study in healthy volunteers.

A pilot study was conducted aiming at specifying sultiame's pharmacokinetic profile, completed by in vitro assays evaluating the intraerythrocytic transfer of sultiame and by a pharmacokinetic model assessing its distribution. Single oral doses of sultiame (Ospolot <sup>®</sup> 50, 100, and 200 mg) were administered in open-label to four healthy volunteers. Serial plasma, whole blood, and urine samples were collected. A spiking experiment was also performed to characterize sultiame's exchanges between plasma and erythrocytes in vitro. Pharmacokinetic parameters were evaluated using standard noncompartmental calculations and nonlinear mixed-effect modeling. The plasma maximal concentrations (C <sub>max</sub> ) showed striking nonlinear disposition of sultiame, with a 10-fold increase while doses were doubled. Conversely, whole blood C <sub>max</sub> increased less than dose proportionally while staying much higher than in plasma. Quick uptake of sultiame into erythrocytes observed in vivo was confirmed in vitro, with minimal efflux. A two-compartment model with first-order absorption, incorporating a saturable ligand to receptor binding, described the data remarkably well, indicating apparent plasma clearance of 10.0 L/h (BSV: 29%) and distribution volume of 64.8 L; saturable uptake into an intracellular compartment of 3.3 L with a maximum binding capacity of 111 mg accounted for nonlinearities observed in plasma and whole blood concentrations. Pharmacokinetic characteristics of sultiame are reported, including estimates of clearance and volume of distribution that were so far unpublished. The noticeable nonlinearity in sultiame disposition should be taken into account for the design of future studies and the interpretation of therapeutic drug monitoring results

Roa, T., Roa, M., Toloza, J. y Navas, L. (Coords.). (2017). Como el agua y el aceite. Conflictos socioambientales por la extracción petrolera. Bogotá D.C.: Centro Nacional Salud, Ambiente y Trabajo, CENSAT Agua Viva, 287 pp.

Como el agua y el aceite. Conflictos socioambientales por la extracción petrolera, es un documento coordinado por Tatiana Roa Avendaño, María Roa García, Jessica Toloza Chaparro y Luisa Navas Camacho, recoge 16 relatos de mujeres acerca de los conflictos socioambientales en cuatro zonas del país: el Piedemonte amazónico-orinocense, la cordillera Oriental, la zona Caribe y la cuenca del Magdalena.Como el agua y el aceite. Conflictos socioambientales por la extracción petrolera, es un documento coordinado por Tatiana Roa Avendaño, María Roa García, Jessica Toloza Chaparro y Luisa Navas Camacho, recoge 16 relatos de mujeres acerca de los conflictos socioambientales en cuatro zonas del país: el Piedemonte amazónico-orinocense, la cordillera Oriental, la zona Caribe y la cuenca del Magdalena

The conformations of MvaU-DNA at various protein concentrations in AFM imaging experiments.

<p>(A) Naked ΦX174 DNA adopting random coiled structure. (B–D) ΦX174 DNA complexed with 30 nM (B), 300 nM (C), and 3 µM (D) MvaU. Blue arrows in panel B indicate small uncoated DNA loops at the end of the DNA bridges. The orange arrows in panel D show large bridges formed through further association or compaction of thinner MvaU nucleoprotein filaments. (E–H) Line profiles of the loop end structures as indicated by the magenta and green lines in panel A–D. The surface area for all the images are 0.7 µm×0.7 µm.</p

The effect of variation in KCl concentration, pH, temperature, and MgCl₂ concentration on MvaU-DNA.

<p>The concentration of MvaU was fixed at 300 nM MvaU at all the conditions tested. (A) Lower KCl concentration results in larger hysteresis or DNA folding. The apparent DNA stiffening is largely unaffected in 50–200 mM KCl. (B) Lower pH value results in larger hysteresis or DNA folding, while the level of DNA stiffening is largely unaffected in the pH range tested. (C) Increase in temperature leads to larger hysteresis or DNA folding, while the level of DNA stiffening is largely unaffected in the temperature range tested. (D) In the presence of MgCl₂, DNA folding is promoted as indicated by increasing amount of hysteresis as the MgCl₂ concentration was increased. The level of DNA stiffening is largely unaffected by variation in MgCl₂ concentration.</p

Sequence alignment and predicted secondary structure of MvaT and MvaU.

<p>(A) The sequence alignment was done with ClustalW2 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0112246#pone.0112246-Larkin1" target="_blank">[46]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0112246#pone.0112246-Goujon1" target="_blank">[47]</a>, with 46% pairwise identity. An * (asterisk) indicates positions which have a single, fully conserved residue, a : (colon) indicates conservation between groups of strongly similar properties, and a . (period) indicates conservation between groups of weakly similar properties. (B) The secondary structures were predicted using a consensus prediction method <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0112246#pone.0112246-Combet1" target="_blank">[48]</a>. Blue vertical bars represent a-helix, red vertical bars represent extended strand, purple vertical bars represent random coil, and gray vertical bars represent ambiguous states.</p

The formation of MvaU nucleoprotein filament effectively blocks DNase1 access to DNA.

<p>Multiple tethers of λ-DNA were completely cleaved in the presence of 100 nM DNase1 after <5 minutes of incubation (black data). In contrast, ∼70% of DNA tethers remained uncut ∼1 hour after the mixture of MvaU/DNase1 was introduced (magenta data), or after the buffer was changed to those containing 100 nM DNase1 without free MvaU in solution (green data).</p