Human pathogenic Yersinia spp. can colonize Steinernema entomopathogenic nematodes

The existence of biological micro-reservoirs explaining the long-term survival of pathogenic bacteria in the environment has long been speculated. Soil invertebrates in particular are suspected to act as intermediary hosts for such pathogenic bacteria and entomopathogenic nematodes (EPNs) were investigated in this respect. To determine whether human pathogenic Yersiniae are able to colonize and multiply in EPNs, a laboratory model was developed. This model consists in Galleria mellonella insect larvae, Steinernema EPNs carrying or not their natural Xenorhabdus symbiont and Yersiniae, brought artificially either in the gut of EPNs or in the haemocoele of the insect larva prior to infection. Using a single direct injection in the insect haemolymph, Y. pseudotuberculosis was recovered from nematodes after seven consecutive EPN infection cycles. As compared to other pathogenic Yersiniae as well as other pathogenic enterobacteria, Y. pseudotuberculosis demonstrated much higher ability to colonize Steinernema EPNs. Genetic determinants potentially involved in the colonization of Steinernema nematodes were knocked out and the resulting Y. pseudotuberculosis mutants were complemented with the corresponding intact genes borne on a low copy plasmid. The EPN colonization capacity of the knockout mutants could not be fully characterized for technical and timing reasons. Nevertheless, our results globally demonstrate long-term persistence of Y. pseudotuberculosis in EPNs in our laboratory conditions. Finally, a method for swapping fluorescent labels in tagged bacteria was developed and used to re-engineer fluorescently labelled Y. pseudotuberculosis. Dual fluorescence confocal microscopic observations showed that the tagged Yersinia colonized distinct Steinernema tissues as compared to the natural Xenorhabdus symbiont of this nematode.(SC - Sciences) -- UCL, 201

La mobilité résidentielle transfrontalière entre le Luxembourg et ses régions voisines : un panorama

International audienceL’article propose un panorama du phénomène de mobilité résidentielle trans-frontalière entre le Luxembourg et ses régions voisines (Lorraine, Wallonie, Rhénanie-Palatinat, Sarre). Le pays voit en effet un nombre croissant de personnes actives le quitter pour s’installer de l’autre côté de la frontière, tout en continuant à travailler au Luxembourg. Les auteurs s’intéressent à l’ampleur du phénomène, aux lieux de départ et d’arrivée, aux motivations des partants et à d’autres facettes caractérisant ce type particulier de mobilité résidentielle

Method for fluorescent marker swapping and its application in Steinernema nematode colonization studies.

An allelic exchange vector was constructed to replace gfp by mCherry in bacteria previously tagged with mini-Tn5 derivatives. The method was successfully applied to a gfp-labeled Yersinia pseudotuberculosis strain and the re-engineered bacterium was used to study the colonization of Steinernema nematodes hosting their Xenorhabdus symbiont using dual-color confocal microscopy

Long-term persistence of Yersinia pseudotuberculosis in entomopathogenic nematodes

Entomopathogenic nematodes (EPNs) are small worms whose ecological behaviour consists to invade, kill insects and feed on their cadavers thanks to a species-specific symbiotic bacterium belonging to any of the genera Xenorhabdus or Photorhabdus hosted in the gastro-intestinal tract of EPNs. The symbiont provides a number of biological functions that are essential for its EPN host including the production of entomotoxins, of enzymes able to degrade the insect constitutive macromolecules and of antimicrobial compounds able to prevent the growth of competitors in the insect cadaver. The question addressed in this study was to investigate whether a mammalian pathogen taxonomically related to Xenorhabdus was able to substitute for or "hijack" the symbiotic relationship associating Xenorhabdus and Steinernema EPNs. To deal with this question, a laboratory experimental model was developed consisting in Galleria mellonella insect larvae, Steinernema EPNs with or without their natural Xenorhabdus symbiont and Yersinia pseudotuberculosis brought artificially either in the gut of EPNs or in the haemocoel of the insect larva prior to infection. The developed model demonstrated the capacity of EPNs to act as an efficient reservoir ensuring exponential multiplication, maintenance and dissemination of Y. pseudotuberculosis

Differential localization of <i>Y. pseudotuberculosis</i> 4N1C and <i>X</i>. sp. TZ03 in <i>Steinernema</i> sp. MW8B nematodes.

<p>Epifluorescence microscope pictures showing axenic EPNs artificially fed on (A) plate-grown red fluorescent <i>Y. pseudotuberculosis</i> 4N1C localizing in the gut (100× magnification) or (B) plate-grown green fluorescent <i>X</i>. sp. TZ03 localizing in a symbiotic vesicle (400× magnification). The latter was still localized in the symbiotic vesicle after 2 consecutive infection cycles on <i>G. mellonella</i> larvae (C) (800× magnification)</p

Growth of <i>Y. pseudotuberculosis</i> 4N1G during EPN’s infection cycles.

<p>The hatched bars show the total counts of <i>Y. pseudotuberculosis</i> 4N1G CFUs retrieved from IJs emerged from a dead moth larva after 1, 4 and 7 consecutive infection cycles (data from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116818#pone.0116818.t002" target="_blank">table 2</a>). The straight line shows the theoretical counts that would be observed starting from the same inoculum if no bacterial division would occur. For this calculation, theoretical volumes of 0.5ml and 0.8nl have been assigned per <i>G. mellonella</i> larva and <i>Steinernema</i> sp MW8B IJ, respectively, and a mean EPN emergence yield of 50,000 EPNs per larva has been considered (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116818#sec002" target="_blank">M&M</a>).</p

Epifluorescence microscope pictures of GFP-labelled <i>Y. pseudotuberculosis</i> 4N1G in <i>Steinernema</i> sp; MW8B EPNs.

<p>A. EPNs emerging from dead moth larvae after 1 (A.1), 4 (A.2) and 7 (A.3) consecutive infection cycles (100× magnification). B. IJs collected after the first infection cycle and stored at 4°C in physiological water for either 8 (B.1, B.2) or 42 days (B.3) (400× magnification). C. IJs collected after the first infection cycle and stored at 28°C in physiological water for 98 days. C.1, enlarged view of the mouth; C.2, enlarged view of the anus; C.3, whole IJ body (400× magnification, 800× magnification for enlarged view).</p

Localization of <i>Y</i>. <i>enterocolitica</i> YE03 in <i>Steinernema</i> sp. MW8B EPNs emerged from an infected larva.

<p>Confocal microscope slides in Z-axis (numbered from 1 to 8) of a <i>Steinernema</i> sp. MW8B EPN colonized by <i>Y. enterocolitica</i> YE03 emerged from the second infection cycle. GFP-labeled bacteria localize in the mouth and in the gut lumen. EPN borders are drawn in white (800× magnification).</p

List of bacterial strains used in this study.

<p>* NCCB, The Netherlands Culture Collection of Bacteria, Utrecht, The Netherlands.</p><p>^§ VAR, Veterinary and Agrochemical Research Center, Brussels, BELGIUM.</p><p>List of bacterial strains used in this study.</p

Evolving the Robotic Technology Kernel to Expand Future Force Autonomous Ground Vehicle Capabilities

This paper presents the conceptual design, development, and implementation of the Robotic Technology Kernel (RTK) in a Polaris GEM e2 by the United States Military Academy\u27s autonomy research team. RTK is the autonomous software suite of the U.S. Army Combat Capabilities Development Command Ground Vehicles Systems Center and to this point has primarily been used within off-road environments. The research team\u27s primary objectives were to verify RTK\u27s platform-agnostic characteristic by implementing the control software on a small, low-speed electric vehicle and augmenting the software to provide the additional capability of operating within an established infrastructure rule set