High adsorption rate is detrimental to bacteriophage fitness in a biofilm-like environment.

BACKGROUND: Bacterial biofilm is ubiquitous in nature. However, it is not clear how this crowded habitat would impact the evolution of bacteriophage (phage) life history traits. In this study, we constructed isogenic lambda phage strains that only differed in their adsorption rates, because of the presence/absence of extra side tail fibers or improved tail fiber J, and maker states. The high cell density and viscosity of the biofilm environment was approximated by the standard double-layer agar plate. The phage infection cycle in the biofilm environment was decomposed into three stages: settlement on to the biofilm surface, production of phage progeny inside the biofilm, and emigration of phage progeny out of the current focus of infection. RESULTS: We found that in all cases high adsorption rate is beneficial for phage settlement, but detrimental to phage production (in terms of plaque size and productivity) and emigration out of the current plaque. Overall, the advantage of high adsorption accrued during settlement is more than offset by the disadvantages experienced during the production and emigration stages. The advantage of low adsorption rate was further demonstrated by the rapid emergence of low-adsorption mutant from a high-adsorption phage strain with the side tail fibers. DNA sequencing showed that 19 out of the 21 independent mutant clones have mutations in the stf gene, with the majority of them being single-nucleotide insertion/deletion mutations occurring in regions with homonucleotide runs. CONCLUSION: We conclude that high mutation rate of the stf gene would ensure the existence of side tail fiber polymorphism, thus contributing to rapid adaptation of the phage population between diametrically different habitats of benthic biofilm and planktonic liquid culture. Such adaptability would also help to explain the maintenance of the stf gene in phage lambda\u27s genome

Effects of bacteriophage traits on plaque formation

<p>Abstract</p> <p>Background</p> <p>The appearance of plaques on a bacterial lawn is one of the enduring imageries in modern day biology. The seeming simplicity of a plaque has invited many hypotheses and models in trying to describe and explain the details of its formation. However, until now, there has been no systematic experimental exploration on how different bacteriophage (phage) traits may influence the formation of a plaque. In this study, we constructed a series of isogenic λ phages that differ in their adsorption rate, lysis timing, or morphology so that we can determine the effects if these changes on three plaque properties: size, progeny productivity, and phage concentration within plaques.</p> <p>Results</p> <p>We found that the adsorption rate has a diminishing, but negative impact on all three plaque measurements. Interestingly, there exists a concave relationship between the lysis time and plaque size, resulting in an apparent optimal lysis time that maximizes the plaque size. Although suggestive in appearance, we did not detect a significant effect of lysis time on plaque productivity. Nonetheless, the combined effects of plaque size and productivity resulted in an apparent convex relationship between the lysis time and phage concentration within plaques. Lastly, we found that virion morphology also affected plaque size. We compared our results to the available models on plaque size and productivity. For the models in their current forms, a few of them can capture the qualitative aspects of our results, but not consistently in both plaque properties.</p> <p>Conclusions</p> <p>By using a collection of isogenic phage strains, we were able to investigate the effects of individual phage traits on plaque size, plaque productivity, and average phage concentration in a plaque while holding all other traits constant. The controlled nature of our study allowed us to test several model predictions on plaque size and plaque productivity. It seems that a more realistic theoretical approach to plaque formation is needed in order to capture the complex interaction between phage and its bacterium host in a spatially restricted environment.</p

The variety mixture strategy assessed in a G × G experiment with rice and the blast fungus Magnaporthe oryzae

Frequent and devastating epidemics of parasites are one of the major issues encountered by modern agriculture. To manage the impact of pathogens, resistant plant varieties have been selected. However, resistances are overcome by parasites requiring the use of pesticides and causing new economical and food safety issues. A promising strategy to maintain the epidemic at a low level and hamper pathogen's adaptation to varietal resistance is the use of mixtures of varieties such that the mix will form a heterogeneous environment for the parasite. A way to find the good combination of varieties that will actually constitute a heterogeneous environment for pathogens is to look for genotype × genotype (G × G) interactions between pathogens and plant varieties. A pattern in which pathogens have a high fitness on one variety and a poor fitness on other varieties guarantees the efficiency of the mixture strategy. In the present article, we inoculated 18 different genotypes of the fungus Magnaporthe oryzae on three rice plant varieties showing different levels of partial resistance in order to find a variety combination compatible with the requirements of the variety mixture strategy, i.e., showing appropriate G × G interactions. We estimated the success of each plant-fungus interaction by measuring fungal fitness and three fungal life history traits: infection success, within-host growth, sporulation capacity. Our results show the existence of G × G interactions between the two varieties Ariete and CO39 on all measured traits and fungal fitness. We also observed that these varieties have different resistance mechanisms; Ariete is good at controlling infection success of the parasite but is not able to control its growth when inside the leaf, while CO39 shows the opposite pattern. We also found that Maratelli's resistance has been eroded. Finally, correlation analyses demonstrated that not all infectious traits are positively correlated. (Résumé d'auteur

316: Diuretic is safe and superior to volume expansion in normotensive patients with acute pulmonary embolism and right ventricular dilatation

BackgroundThe rational and the benefit of load expansion is controversial in acute pulmonary embolism (PE). Diuretic may reduce RV preload and improve hemodynamic status. The present study reported the safety of furosemide in normotensive acute PE with oligo-anuria.Methods and ResultsWe prospectively included 68 consecutive normotensive patients (systolic blood pressure ≥90mmHg) admitted for acute PE with oligoanuria and RV dilation. RV dilation was defined by a right and left ventricular diameter ratio >0.6. Overall, 29 patients were treated by a repeated bolus of furosemide (83±84mg, range 40 to 160mg), while 39 patients received isotonic saline solution (1.6±0.8 L, range, 0.5 to 4,0L). Patients treated by furosemide and fluid expansion had similar severity of hypoxemia but the furosemide group had lower admission blood pressure (119±21mmHg vs. 132±18mmHg, P=0.007) and greater shock index defined as heart rate and blood pressure ratio (0.81±0.23 vs. 0.69±0.18, P=0.02). Despite these differences, only the furosemide group had decrease shock index (0.81±0.23 vs. 0.62±0.17, P<0.0001) with improved systolic blood pressure (119±21mmHg vs. 133 ±18mmHg, P<0.001), heart rate (93±19bpm vs. 81±18bpm, P<0.001), and creatinin level. Finally, more patients were weaned in oxygen at 24 hours (39% vs. 19%) and in-hospital survival without death and PE-related shock was similar between the two groups (93% vs. 95%).ConclusionsIn normotensive PE with oligoanuria and RV dilatation, diuretic can be safely delivered to improve systolic blood pressure and oxygenation

Pharmacological analysis of transmission activation of two aphid-vectored plant viruses, turnip mosaic virus and cauliflower mosaic virus

Turnip mosaic virus (TuMV, family Potyviridae) and cauliflower mosaic virus (CaMV, family Caulimoviridae) are transmitted by aphid vectors. They are the only viruses shown so far to undergo transmission activation (TA) immediately preceding plant-to-plant propagation. TA is a recently described phenomenon where viruses respond to the presence of vectors on the host by rapidly and transiently forming transmissible complexes that are efficiently acquired and transmitted. Very little is known about the mechanisms of TA and on whether such mechanisms are alike or distinct in different viral species. We use here a pharmacological approach to initiate the comparison of TA of TuMV and CaMV. Our results show that both viruses rely on calcium signaling and reactive oxygen species (ROS) for TA. However, whereas application of the thiol-reactive compound N-ethylmaleimide (NEM) inhibited, as previously shown, TuMV transmission it did not alter CaMV transmission. On the other hand, sodium azide, which boosts CaMV transmission, strongly inhibited TuMV transmission. Finally, wounding stress inhibited CaMV transmission and increased TuMV transmission. Taken together, the results suggest that transmission activation of TuMV and CaMV depends on initial calcium and ROS signaling that are generated during the plant's immediate responses to aphid manifestation. Interestingly, downstream events in TA of each virus appear to diverge, as shown by the differential effects of NEM, azide and wounding on TuMV and CaMV transmission, suggesting that these two viruses have evolved analogous TA mechanisms

120 Superiority of CT scan over transthoracic echocardiography in predicting aortic regurgitation after TAVI

BackgroundParavalvular aortic regurgitation (AR) occurs in up to 86% of patients undergoing Transcatheter Aortic Valve Implantation (TAVI). Its prevalence remains unchanged after one year follow-up but its determinants are unclear. We sought to evaluate the impact of annulus measurement by transthoracic echocardiography (TTE) and by CT scan on the occurrence of AR.MethodsThe study included 43 symptomatic patients (83±8 years, 72% in NYHA≥III) with severe aortic stenosis [0.76±0.19cm2, mean gradient 42±14mmHg] who underwent TAVI using CoreValve® LLC Percutaneous Aortic Valve Implantation System, Medtronic, Minneapolis USA. Left ventricular outflow tract (LVOT) area was computed from LVOT diameter (21±2mm) by TTE using a spherical model and from CT using an ellipsoidal model according to the larger (25±3mm) and the smaller outflow tract diameters (22±3mm). These data were compared to the prosthesis area and the occurrence of AR after TAVI.ResultsIn patients with AR greater or equal to 2/4 (32%), LVOT area measured by CT was significantly greater as compared to patients with no or mild AR (478±65mm 2 vs. 411±85mm2, p=0.009). Furthermore, the difference between actual prosthesis area and LVOT area measured by CT scan was significantly smaller (113±55 vs. 171±67, p=0.009) in patients with significant AR (≥2/4) after TAVI. In contrast, LVOT area from TTE did not correlate with AR severity.ConclusionCT scan is more accurate than TTE for calculating LVOT area for prosthesis sizing before TAVI in order to avoid post-implantation AR

Cellular Postconditioning: Allogeneic Cardiosphere-Derived Cells Reduce Infarct Size and Attenuate Microvascular Obstruction When Administered After Reperfusion in Pigs With Acute Myocardial Infarction

Intracoronary (IC) delivery of cardiosphere-derived cells (CDCs) has been demonstrated to be safe and effective in porcine and human chronic myocardial infarction (MI). However, IC delivery of CDCs after reperfusion in acute MI has never been assessed in a clinically-relevant large animal model. We tested CDCs as adjunctive therapy to reperfusion in a porcine model of MI

Renovering av Lyon Part-Dieu : Innovativ byggarbetsplatser skötsel i en tät stadsmiljö

This study aims at identifying on a concrete example the possible transfer of methods from strategic spatial planning to lower scales of planning like urban programming or operational planning of construction sites. Strategic spatial planning is a participatory and open method establishing the basis for cooperation between public and private stakeholders to achieve what is defined by said stakeholders as the best evolution for the territory it is dealing with, it relies on tools and processes like territorial diagnosis, thematic workshops and roundtables; Objectives are more qualitatively than quantitatively defined to allow flexibility to adapt to internal and external changes. This paper considers the territory of Lyon conurbation, France, as its territory of focus and particularly the redevelopment project of its central business district and multimodal hub, Part-Dieu. The planning of Lyon conurbation was in the 80s at the vanguard of strategic planning in France. Driven by Lyon urban planning agency and Grand Lyon, the local authority in charge of the area, under the pressure of local economic actors, Lyon conurbation acquired and integrated new tools and methods from strategic spatial planning. The hypothesis of this study is that, from then on, strategic planning methods and processes got transferred from the field of pure strategic spatial planning to the lower notches of the decision-making chain leading to the realization of a project: the stage of the programming of a neighborhood – the Part-Dieu district – and the stage of the operational planning of a construction or redevelopment operation. This study puts forward the following reasoning to explain this transfer of methods: an acculturation process to the collaborative and qualitative methods of strategic spatial planning took place in the territory of Lyon conurbation. It happened between the corporate cultures of spatial planning and those of urban program design and construction operation management. However, more than a way to really involve all stakeholders in the decision-making process in a bottom-up approach, this study suggests that the use of these methods at the stage of construction/redevelopment operation management is more of a facade to make stakeholders better accept decisions already taken by experts and/or public authorities. One could talk about a top-down approach disguised as a bottom-up approach

Small bottleneck size in Faba bean necrotic stunt virus populations during aphid transmission

BGPI : équipe 2Small bottleneck size in Faba bean necrotic stunt virus populations during aphid transmission. 16. Rencontres de Virologie Végétale (RVV 2017