Toxic effect and inability of L-homoserine to be a nitrogen source for growth of Escherichia coli resolved by a combination of in vivo evolution engineering and omics analyses

L-homoserine is a pivotal intermediate in the carbon and nitrogen metabolism of E. coli. However, this non-canonical amino acid cannot be used as a nitrogen source for growth. Furthermore, growth of this bacterium in a synthetic media is potently inhibited by L-homoserine. To understand this dual effect, an adapted laboratory evolution (ALE) was applied, which allowed the isolation of a strain able to grow with L-homoserine as the nitrogen source and was, at the same time, desensitized to growth inhibition by this amino acid. Sequencing of this evolved strain identified only four genomic modifications, including a 49 bp truncation starting from the stop codon of thrL. This mutation resulted in a modified thrL locus carrying a thrL* allele encoding a polypeptide 9 amino acids longer than the thrL encoded leader peptide. Remarkably, the replacement of thrL with thrL* in the original strain MG1655 alleviated L-homoserine inhibition to the same extent as strain 4E, but did not allow growth with this amino acid as a nitrogen source. The loss of L-homoserine toxic effect could be explained by the rapid conversion of L-homoserine into threonine via the thrL*-dependent transcriptional activation of the threonine operon thrABC. On the other hand, the growth of E. coli on a mineral medium with L-homoserine required an activation of the threonine degradation pathway II and glycine cleavage system, resulting in the release of ammonium ions that were likely recaptured by NAD(P)-dependent glutamate dehydrogenase. To infer about the direct molecular targets of L-homoserine toxicity, a transcriptomic analysis of wild-type MG1655 in the presence of 10 mM L-homoserine was performed, which notably identified a potent repression of locomotion-motility-chemotaxis process and of branched-chain amino acids synthesis. Since the magnitude of these effects was lower in a ΔthrL mutant, concomitant with a twofold lower sensitivity of this mutant to L-homoserine, it could be argued that growth inhibition by L-homoserine is due to the repression of these biological processes. In addition, L-homoserine induced a strong upregulation of genes in the sulfate reductive assimilation pathway, including those encoding its transport. How this non-canonical amino acid triggers these transcriptomic changes is discussed

Regards comparatistes sur la réforme de la responsabilité civile: le rapprochement des responsabilités contractuelle et délictuelle dans l’avant-projet de réforme, abordé sous l’angle du droit compare

This article is a comparative study of the Dutch and French legal systems regarding four major points of the French governmental reform project for civil liability : concurrence of actions; limitation and exemption clauses; causation; the obligation to mitigate your own damage. It also addresses the following issues: the question of damages to the environment, and the role of transitional provisions. Through these different areas of study, this article shows that the traditional distinction between contractual and tortuous liability is not necessarily relevant and may even prove a nuisance in certain cases. The contribution is followed by a reaction of Mme. De Cabarrus, magistrate at the French Ministry of Justice

Quaternion based control for robotic observation of marine diversity

International audienceIn the current context of increasing pressures on marine ecosystems, one of the main challenge of ecology is to be able to conduct accurate and reliable assessment of biodiversity. Until now, studies are mainly performed by divers, which induces high cost and heavy logistic on terrain missions and are limited to few meters depth. An underwater robot could be a solution to most limitations of human-operated observation (divers) in underwater environment, but requires to be specialized according to expert protocols and objectives. This paper presents the design of the control architecture of an underwater hybrid vehicle, where control is distributed among expert (marine biologists) and autonomous system. The analysis of expert protocols drives the control design, resulting in a composition of 'functioning modes', according to the chosen observation strategy and the appropriate control distribution (operator/robot) and actuators allocation (redundant thrusters). We present here the design of the different control laws dedicated to each functioning mode (observation strategy). The performance of the solution is evaluated on the simulator of the ROV Ulysse

Datasets from a ground based model of microgravity

Recherche Data Gouv repositoryData presentation Sequential 11 day data of a murin model for hindlimb suspension subdivided as a 3-day control period, a 5-day suspension period, a 2-day recovery period and a brief re-suspension. Physiological parameters (Sys(mmHg):Pressure, Dia(mmHg):Pressure, Mean(mmHg):Pressure, +dP/dt(mmHg/ms):Pressure, -dP/dt(mmHg/ms):Pressure, HR(bpm):Pressure, HR(bpm):ECG, RR-I(ms):ECG, R-H(mV):ECG, QRS(ms):ECG, QT-I(ms):ECG, QTcb(ms):ECG, QTcf(ms):ECG, QTcv(ms):ECG, T_NPMN(Celsius):Temp, A_NPMN(Counts):Activity) are provided as two-hour time bins datasets from HD-X11 transmitters (Data Science International®, DSI, Saint Paul MN, USA) and telemetric receivers (RPC-1 PhysioTelTM Receivers, DSI). Research purpose It remains unclear how the autonomic nervous system adapts to short and long duration missions. On board studies are limited due to high costs and difficulties in obtaining data during missions; therefore, our data is mainly from ground-based models. Yet, the hemodynamic and autonomic responses during simulated microgravity using these models remain controversial. The controversy is likely rooted in the heterogeneity between species, the differences in both the duration of microgravity exposure as well as the choice of time points for recorded measures. We sought to clarify various controversial aspects of these forms of experiments by devising a murine hindlimb unloading (HU) model with continuous monitoring of relevant parameters. We aimed to define the kinetics of cardiovascular adaptation and recovery using a murine HU model during three phases over 10 days: 3 days of control, 5 days of HU and 2 days of recovery. Using implantable radio telemetry devices, we continuously collected data on mouse subcutaneous temperature and locomotor activity, as well as cardiac parameters, arterial blood pressure (ABP), heart rate (HR). The cardiac parameters were further exploited to calculate heart rate variability (HRV) and baroreflex sensitivity (BRS). We also performed complementary experiments on 6 subjects to monitor temperature fluctuations. We found that HU induced an immediate, dramatic and persistent decrease in locomotor activity and temperature (subcutaneous and central recorded temperature). On the other hand, the cardiac response was varied. We observed an initial bradycardia associated with an increase in vagal activity and baroreflex sensitivity together with a decrease in water intake. These findings indicate early adaptation to fluid redistribution. Analyses of the complete data set revealed effects on cardiovascular circadian rhythms during HU that are exacerbated during the recovery phase. Our investigation with continuous monitoring has both provided a degree of clarity with regard to the conflicting information in the literature and provided us with insights into how to better design these types of experiments in the future

Aquatic eDNA for monitoring French Guiana biodiversity

International audienc

Glycosylated Amphiphilic Calixarene‐Based Detergent for Functional Stabilization of Native Membrane Proteins.

International audienc

Atelier débitmétrie liquide à surface libre

National audienceInitié en 2005, l'atelier "Débitmétrie liquide à surface libre" avait pour objectif le recensement des méthodes utilisées à Irstea pour mesurer le débit des cours d'eau. Le travail de synthèse suite aux au résultat d'une enquête et de réunions est maintenant accessible via l'intranet du réseau mesure. Doté de quarante fiches, cet outil recense les techniques de mesure de débit utilisées a Irstea ; notamment dans les bassins versants expérimentaux (Orgeval, Draix, Real Colobrier, Yzeron) et par les différentes équipes utilisant l'hydrométrie. Cet outil a pour but de donner une vision d'ensemble des compétences et du matériel disponible à Irstea. Il peut permettre à un jeune chercheur, un doctorant, un technicien de se renseigner rapidement sur une méthode, d'avoir directement des contacts pour affiner la construction d'une station de mesure ou pour choisir une technique plutôt qu'une autre. A partir de ce premier travail nous avons identifié des besoins à plusieurs niveaux : •Le contrôle et l'étalonnage des courantomètres. •Le calcul du débit et de son incertitude. •Le partage de connaissances sur les méthodes et les pratiques des hydromètres. Lors d'une réunion de l'atelier en 2010 le groupe décide d'organiser un test pour comparer les techniques et les protocoles de mesures utilisés dans les différentes équipes pour mesurer les débits par exploration du champ des vitesses notamment. Des inter-comparaisons d'instruments de mesures de débit sont pratiquées dans différents domaines. L'organisation et l'exploitation des inter-comparaisons sont décrites dans les normes (en particulier ISO 5725-2). L'objectif recherché est ici de déterminer la performance d'une méthode : le jaugeage par exploration des vitesses au courantomètre sur perche. L'atelier a organisé un premier test en mai 2011 sur l'Ouvèze et le Toulourenc (84) rassemblant 11 équipes qui a donné des résultats très intéressants. Une seconde campagne avec 13 équipes a eu lieu en octobre 2013 sur le Cernon et le Durzon (12). Ces deux campagnes de mesure ont permis de comparer les valeurs d'incertitudes évaluées à partir d'un jaugeage (Norme ISO 748) et celles obtenues par comparaison inter-laboratoire