Variations in Arterial Blood Pressure after Kidney Transplantation

The course of hypertension within the first 2 months after kidney transplantation was correlated with renal function, plasma renin activity (PRA), and the daily maintenance dose of prednisone in 18 homograft recipients. During acute rejection blood pressure (BP) closely correlated with PRA. Patients with normal homograft function showed an increase in BP early after transplantation which in most returned to normal 3-8 weeks later. In the latter group no correlation could be found between the level of BP and PRA, however the BP correlated closely with the dose of prednisone. These observations suggest that during acute rejection the increase in BP may at least partly be mediated by a renal pressor mechanism, whereas with normal renal function the high dose of glucocorticoids may play an important role in the development of hypertension.</jats:p

A New Member of the Growing Family of Contact-Dependent Growth Inhibition Systems in Xenorhabdus doucetiae

Xenorhabdus is a bacterial symbiont of entomopathogenic Steinernema nematodes and is pathogenic for insects. Its life cycle involves a stage inside the insect cadaver, in which it competes for environmental resources with microorganisms from soil and the insect gut. Xenorhabdus is, thus, a useful model for identifying new interbacterial competition systems. For the first time, in an entomopathogenic bacterium, Xenorhabdus doucetiae strain FRM16, we identified a cdi-like locus. The cdi loci encode contact-dependent inhibition (CDI) systems composed of proteins from the two-partner secretion (TPS) family. CdiB is the outer membrane protein and CdiA is the toxic exoprotein. An immunity protein, CdiI, protects bacteria against inhibition. We describe here the growth inhibition effect of the toxic C-terminus of CdiA from X. doucetiae FRM16, CdiA-CTFRM16, following its production in closely and distantly related enterobacterial species. CdiA-CTFRM16 displayed Mg2+-dependent DNase activity, in vitro. CdiA-CT (FRM16)-mediated growth inhibition was specifically neutralized by CdiI(FRM16). Moreover, the cdi(FRM16) locus encodes an ortholog of toxin-activating proteins C that we named CdiC(FRM16). In addition to E. coli, the cdiBCAI-type locus was found to be widespread in environmental bacteria interacting with insects, plants, rhizospheres and soils. Phylogenetic tree comparisons for CdiB, CdiA and CdiC suggested that the genes encoding these proteins had co-evolved. By contrast, the considerable variability of CdiI protein sequences suggests that the cdiI gene is an independent evolutionary unit. These findings further characterize the sparsely described cdiBCAI-type locus

Inhibition of Spodoptera frugiperda phenoloxidase activity by the products of the Xenorhabdus rhabduscin gene cluster

We evaluated the impact of bacterial rhabduscin synthesis on bacterial virulence and phenoloxidase inhibition in a Spodoptera model. We first showed that the rhabduscin cluster of the entomopathogenic bacterium Xenorhabdus nematophila was not necessary for virulence in the larvae of Spodoptera littoralis and Spodoptera frugiperda. Bacteria with mutations affecting the rhabduscin synthesis cluster (ΔisnAB and ΔGT mutants) were as virulent as the wild-type strain. We then developed an assay for measuring phenoloxidase activity in S. frugiperda and assessed the ability of bacterial culture supernatants to inhibit the insect phenoloxidase. Our findings confirm that the X. nematophila rhabduscin cluster is required for the inhibition of S. frugiperda phenoloxidase activity. The X. nematophila ΔisnAB mutant was unable to inhibit phenoloxidase, whereas ΔGT mutants displayed intermediate levels of phenoloxidase inhibition relative to the wild-type strain. The culture supernatants of Escherichia coli and of two entomopathogenic bacteria, Serratia entomophila and Xenorhabdus poinarii, were unable to inhibit S. frugiperda phenoloxidase activity. Heterologous expression of the X. nematophila rhabduscin cluster in these three strains was sufficient to restore inhibition. Interestingly, we observed pseudogenization of the X. poinarii rhabduscin gene cluster via the insertion of a 120 bp element into the isnA promoter. The inhibition of phenoloxidase activity by X. poinarii culture supernatants was restored by expression of the X. poinarii rhabduscin cluster under the control of an inducible Ptet promoter, consistent with recent pseudogenization. This study paves the way for advances in our understanding of the virulence of several entomopathogenic bacteria in non-model insects, such as the new invasive S. frugiperda species in Africa

A New Member of the Growing Family of Contact-Dependent Growth Inhibition Systems in Xenorhabdus doucetiae

Xenorhabdus is a bacterial symbiont of entomopathogenic Steinernema nematodes and is pathogenic for insects. Its life cycle involves a stage inside the insect cadaver, in which it competes for environmental resources with microorganisms from soil and the insect gut. Xenorhabdus is, thus, a useful model for identifying new interbacterial competition systems. For the first time, in an entomopathogenic bacterium, Xenorhabdus doucetiae strain FRM16, we identified a cdi-like locus. The cdi loci encode contact-dependent inhibition (CDI) systems composed of proteins from the two-partner secretion (TPS) family. CdiB is the outer membrane protein and CdiA is the toxic exoprotein. An immunity protein, CdiI, protects bacteria against inhibition. We describe here the growth inhibition effect of the toxic C-terminus of CdiA from X. doucetiae FRM16, CdiA-CTFRM16, following its production in closely and distantly related enterobacterial species. CdiA-CTFRM16 displayed Mg2+-dependent DNase activity, in vitro. CdiA-CT (FRM16)-mediated growth inhibition was specifically neutralized by CdiI(FRM16). Moreover, the cdi(FRM16) locus encodes an ortholog of toxin-activating proteins C that we named CdiC(FRM16). In addition to E. coli, the cdiBCAI-type locus was found to be widespread in environmental bacteria interacting with insects, plants, rhizospheres and soils. Phylogenetic tree comparisons for CdiB, CdiA and CdiC suggested that the genes encoding these proteins had co-evolved. By contrast, the considerable variability of CdiI protein sequences suggests that the cdiI gene is an independent evolutionary unit. These findings further characterize the sparsely described cdiBCAI-type locus

Phylogenetic analysis of CdiI^FRM16 orthologous sequences

<p>Phylogenetic trees were constructed by the maximum likelihood (ML) method, with bootstrap values indicated at the nodes. The branch length scale bar below the phylogenetic tree reflects the numbers of amino-acid substitutions per site. The protein sequences are split into three clades, I, II and III, indicated at the right of the tree. Accession numbers of the sequences are indicated in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0167443#pone.0167443.s002" target="_blank">S2 Table</a>.</p

Inventory of <i>cdiBCAI</i>-type loci in <i>Xenorhabdus</i> and <i>Photorhabdus</i> genomes.

<p>Inventory of <i>cdiBCAI</i>-type loci in <i>Xenorhabdus</i> and <i>Photorhabdus</i> genomes.</p

A New Member of the Growing Family of Contact-Dependent Growth Inhibition Systems in <i>Xenorhabdus doucetiae</i> - Fig 1

<p><b>The <i>cdiBCAI</i> locus of <i>Xenorhabdus doucetiae</i> FRM16 A</b>. <b>Genetic organization of the <i>cdiBCAI</i> locus</b> Boxes represent genes. Gene labels are shown above the boxes. The putative <i>cdiA</i> and <i>cdiB</i> genes are shown in blue. The <i>cdiA</i>-CT region is indicated. The location of the nucleotide sequence encoding the VENN motif is indicated in yellow. <b>B. The <i>cdiBCAI</i> locus is located in an integrative conjugative element (ICE).</b> The <i>cdi</i> locus is shown in blue. The conserved genes of the ICE, as defined in a previous study [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0167443#pone.0167443.ref040" target="_blank">40</a>], are highlighted in green. Notable cargo genes (e.g. potentially involved in host interactions) are highlighted in red. The label numbers of the genes are indicated above the locus. The ICE is embedded in a large genomic island inserted between the <i>fba</i> and <i>mltC</i> genes (black boxes). The genetic content of the genomic island is described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0167443#pone.0167443.s003" target="_blank">S3 Table</a>.</p

Phylogenetic analysis of CdiC ^FRM16 orthologous sequences

<p>Phylogenetic trees were constructed by the maximum likelihood (ML) method, with bootstrap values indicated at the nodes. The branch length scale bar below the phylogenetic tree reflects the numbers of amino-acid substitutions per site. The protein sequences are split into two clades, I and II, indicated at the right of the tree. The ecological niches are symbolized by pictograms (insects, rhizosphere, water, plants, and vertebrates). Accession numbers of the sequences are indicated in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0167443#pone.0167443.s002" target="_blank">S2 Table</a>.</p

CdiA-CT^FRM16 inhibits cell growth when expressed in <i>E</i>. <i>coli</i> and <i>Xenorhabdus bovienii</i>.

<p><b>A. CdiA-CT</b>^<b>FRM16</b><b>–mediated growth inhibition in <i>X</i>. <i>bovienii</i> strain CS03 growth.</b><i>X</i>. <i>bovienii</i> CS03 carrying pGJ907 (black lines), or pGJ907_<i>cdiA</i>-CT^FRM16 (red lines) was grown at 28°C in LB broth supplemented with kanamycin (dotted curves), or LB broth supplemented with kanamycin plus aTc (continuous curves). <b>B. CdiA-CT</b>^<b>FRM16</b><b>–mediated growth inhibition in <i>E</i>. <i>coli</i> EPI400.</b> <i>E</i>. <i>coli</i> EPI400 carrying pGJ907 (black lines) or pGJ907_<i>cdiA</i>-CT^FRM16 (red lines) was grown at 37°C in LB broth supplemented with kanamycin (dotted curves), or LB broth supplemented with kanamycin plus aTc (continuous curves). <b>C. XDD1-1120 confers immunity to CdiA-CT</b>^<b>FRM16</b> <b>toxicity in <i>E</i>. <i>coli</i> EPI400.</b> <i>E</i>. <i>coli</i> carrying pGJ907 and pUC18 (black line), pGJ907_<i>cdiA</i>-CT^FRM16 and pUC18 (red line), pGJ907_<i>cdiA</i>-CT^FRM16 and pUC18_ XD1120 (blue line), pGJ907_<i>cdiA</i>-CT^FRM16 and pUC18_ XD1118 (green line) were grown at 37°C in LB broth supplemented with kanamycin. The times when IPTG and aTc were added at the culture are indicated by an arrow. In each panel, optical density at 600 nm was recorded every 30 minutes. When required, aTc was added 2 hours after the start of culture (OD_{600 nm}~0.15). The results shown are the mean and standard deviation of three experiments.</p

Ail and PagC-Related Proteins in the Entomopathogenic Bacteria of Photorhabdus Genus

Among pathogenic Enterobacteriaceae, the proteins of the Ail/OmpX/PagC family form a steadily growing family of outer membrane proteins with diverse biological properties, potentially involved in virulence such as human serum resistance, adhesion and entry into eukaryotic culture cells. We studied the proteins Ail/OmpX/PagC in the bacterial Photorhabdus genus. The Photorhabdus bacteria form symbiotic complexes with nematodes of Heterorhabditis species, associations which are pathogenic to insect larvae. Our phylogenetic analysis indicated that in Photorhabdus asymbiotica and Photorhabdus luminescens only Ail and PagC proteins are encoded. The genomic analysis revealed that the Photorhabdus ail and pagC genes were present in a unique copy, except two ail paralogs from P. luminescens. These genes, referred to as ail1Pl and ail2Pl, probably resulted from a recent tandem duplication. Surprisingly, only ail1Pl expression was directly controlled by PhoPQ and low external Mg2+ conditions. In P. luminescens, the magnesium-sensing two-component regulatory system PhoPQ regulates the outer membrane barrier and is required for pathogenicity against insects. In order to characterize Ail functions in Photorhabdus, we showed that only ail2Pl and pagCPl had the ability, when expressed into Escherichia coli, to confer resistance to complement in human serum. However no effect in resistance to antimicrobial peptides was found. Thus, the role of Ail and PagC proteins in Photorhabdus life cycle is discussed