Simulated Microgravity Created Using a Random Positioning Machine Induces Changes in the Physiology of the Fusarium solani Species Complex

Fusarium is a phytopathogenic fungus involved in human pathology and is present in space stations. It is essential to understand the effects of microgravity on the physiology of this fungus to determine the potential risks to the health of crew members and to propose the necessary countermeasures. This study aimed to determine changes in the physiological parameters of the Fusarium solani species complex under simulated microgravity generated using a random positioning machine (RPM) and phenotypic approaches. We observed increased growth, spore production, and germination while biofilm production was reduced under RPM exposure. These in vitro data show the importance of further studying this fungus as it has been repeatedly demonstrated that microgravity weakens the immune system of astronauts

Exploiting Catabolite Repression and Stringent Response to Control Delay and Multimodality of Bioluminescence Signal by Metal Whole-Cell Biosensors: Interplay between Metal Bioavailability and Nutritional Medium Conditions

International audienceThe time-dependent response of metal-detecting whole-cell luminescent bacterial sensors is impacted by metal speciation/bioavailability in solution. The comprehensive understanding of such connections requires the consideration of the bacterial energy metabolism at stake and the effects of supplied food on cells’ capability to convert bioaccumulated metals into light. Accordingly, we investigated the time response (48 h assay) of PzntA-luxCDABE Escherichia coli Cd biosensors in media differing with respect to sources of amino acids (tryptone or Lysogeny Broth) and carbon (glucose, xylose and mixtures thereof). We show that the resulting coupling between the stringent cell response and glucose/xylose-mediated catabolite repressions lead to well-defined multimodalities and shapes of the bioluminescence signal over time. Based on a recent theory for the time–response of metal-sensing luminescent bacteria, successful theoretical reconstructions of the bioluminescence signals are reported under all Cd concentrations (0–20 nM) and nutritive conditions examined. This analysis leads to the evaluation of time-dependent cell photoactivity and qualitative information on metal speciation/bioavailability in solution. Biosensor performance and the position, shape, number, and magnitude of detected peaks are discussed in relation to the metabolic pathways operative during the successive light emission modes identified here over time. Altogether, the results clarify the contributions of metal/nutrient bio-availabilities and food quality to cell response typology

Comparative Analysis of Cell Metabolic Activity Sensing by Escherichia coli rrnB P1-lux and Cd Responsive-Lux Biosensors: Time-Resolved Experiments and Mechanistic Modelling

International audienceWhole-cell bacterial sensors are used in medical/environmental applications to detect chemicals, and to assess medium toxicity or stress. Non-specific constitutive biosensors generally serve the latter purpose, whereas chemical detection is performed with biosensors involving a specific chemical-inducible promoter. Herein, we show that functioning principles of specific and nonspecific whole-cell biosensors are not exclusive as both can probe modulations of cell metabolic activity under stressing conditions. The demonstration is based on (i) time-resolved measurements of bioluminescence produced by constitutive rrnB P1-luxCDABE Escherichia coli biosensor in media differing with respect to carbon source, (ii) theoretical reconstruction of the measured signals using a here-reported theory for bioluminescence generated by constitutive cells, (iii) comparison between time-dependent cell photoactivity (reflecting metabolic activity) retrieved by theory with that we reported recently for cadmium-inducible PzntA-luxCDABE E. coli in media of similar compositions. Whereas signals of constitutive and non-constitutive biosensors differ in terms of shape, amplitude and peak number depending on nutritional medium conditions, analysis highlights the features shared by their respective cell photoactivity patterns mediated by the interplay between stringent response and catabolite repressions. The work advocates for the benefits of a theoretical interpretation for the time-dependent response of biosensors to unravel metabolic and physicochemical contributions to the bioluminescence signal

Gut Microbiota of Zebra Mussels (Dreissena polymorpha) as a Holobiont Concept- Significantly Reliable Method for Aquatic Environment Monitoring?

International audienceFrance's Water bodies are constantly exposed to emerging pollutants from urban areas. It requires constant monitoring of contamination. Zebra mussel (ZM) is an invasive species which is spread in European waters extensively. They are filter feeders that filter a large amount of water as its food source. They process and remove a high number of microorganisms (MO). ZM accumulate compounds from the water column and is an excellent indicator of the surrounding environment. The filtration process allows ZMs to absorb naturally occurring mixtures and pollutants. ZM's gut microbiota (GM) contains a high number of MO and creates a specific symbiosis with the host. It is closely connected to the outside environment and represents aquatic conditions. It shows the importance of holobiont symbiosis and its need for detailed understanding. This study investigates the GM of ZM as an indicator of emerging contaminants such as human pathogens and antibiotics resistance bacteria (ARB). The inquiry is how GM is affected by variations of diet, pathogens and contaminants appearing in aquatic environments and the overall understanding of the gut microbiota of ZMs and its essence in the accumulation of increasing quantities of pathogens and ARB.ZMs were collected in the field and let acclimated before following steps. After the acclimation period, the field investigation selected ZMs were transferred to appointed sites and put into specially created devices for collecting faeces. The rest of the ZMs were kept in laboratory conditions to further study their gastrointestinal microbiota. Further analysis will be performed by 16S rDNA sequencing and cultivation.The experiment combines laboratory-controlled conditions and field experiments. Obtaining data from different feeding conditions, filtration rates and the overall effect of the laboratory and field environment and possible accumulation of pathogens and ARB from the field is critical for further study. Testing of water bodies can be more reliable with ZMs accumulation of contaminants with comparison to regular grab water samples depending on many factors.This study emphasises the importance of the microbiota of filter feeders and their ability to accumulate compounds from the water

Kinetics of metal detection by luminescence-based whole-cell biosensors: connecting biosensor response to metal bioavailability, speciation and cell metabolism

International audienceLuminescent whole-cell metal biosensors are genetically engineered cells used for the detection of metals in e.g. aqueous solutions. Herein, we detail the quantitative connections between time-response of luminescent bacterial metal sensors and the bioavailability of free and complexed metal species. To that end, we formulate the biophysicochemical dynamics of metal partitioning at a biosensor/solution interface and integrate the required metabolism contribution to cell response. The formalism explains the ways in which cell signal depends on: coupled Eigen kinetics of metal complexation and diffusion of metal species to/from the interface; kinetics of metal excretion, Michaelis–Menten bioaccumulation and ensuing metal depletion from bulk solution; and kinetics of bioluminescence production following intracellular metal sequestration by regulatory metalloproteins. In turn, an expression is derived for the time-dependent cell signal as a function of interrelated (bioavai)lability of metal species and (thermo)dynamic descriptors of extra/intracellular metal complexation. Quantitative criteria are elaborated to identify scenarios where equilibrium modeling of metal speciation is incorrect, bulk metal depletion is operative, metal biouptake kinetics is governed by metal diffusion, or labile metal complexes fully contribute to cell response. Remarkably, in agreement with experiments, the theory predicts time-shifts of bioluminescence peaks with increasing concentration of biosensor and/or metal ligand in solution. We show that these shifts originate from the crosstalk between activation kinetics of cell photoactivity and speciation-dependent kinetics of bulk metal depletion. Overall, the work paves the way for the elaboration of new strategies to exploit the bioluminescence response of metal lux-biosensors at a dynamic level and evaluate metal bioavailability properties in environmental or biological aqueous samples

Delta-2-Troglitazone targets mitochondria in triple-negative breast cancer cells: a metabolic change contributing to sensitization of cancer cells to chemotherapy?

Présentation PosterNational audienceBackground: Resistance to conventional therapies for triple-negative mammary tumors are strong arguments for the search for new therapeutic agents. A strategy is to develop drugs targeting energetic metabolism to sensitize cancer cells to chemotherapy. Thiazolidinediones display antiproliferative effects which could be the result of mechanisms altering cell metabolism. Our objectives are to characterize the modifications of the triple-negative breast cancer cell line MDA-MB231 metabolism after Delta-2-Troglitazone (D2T) exposure and to define whether D2T could potentiate the action of chemotherapeutic agents.Methods: Cell numbers were assessed by crystal violet staining. NAD+ and NADH concentrations were determined by chemiluminescence. Lactate and glucose concentrations were measured with an YSI 2950 Biochemistry Analyzer. Mitochondrial activity was assessed by oxygraphy. Results: 48h cell treatment with D2T (75 µM) inhibited cell proliferation. At the metabolic level, NAD+/NADH ratio was increased after a 24h treatment, suggesting that glycolysis and/or mitochondrial respiration could be altered. Oxygen consumption was diminished after a 24h exposure to D2T, associated with a decreased mitochondrial efficiency and a mitochondrial decoupling. At the glycolytic level, lactate production and glucose consumption were increased in D2T-treated cells. Finally, D2T at a lower dose (15 µM) potentiated the effects of 2-DG (2-Deoxyglucose, a glycolytic inhibitor) and doxorubicin on cell viability. Conclusion: D2T induces metabolic changes in cancer cells MDA-MB231. D2T targets mitochondrial activity likely leading to the stimulation of glycolysis. Besides, a low dose of D2T potentiates the action of 2-DG and doxorubicin on cell viability. The impact of the D2T/doxorubicin combination on proliferation and apoptosis has to be characterized. Overall, the link between the metabolic alteration observed with D2T and its antiproliferative effect has to be demonstrated

Comparaison des réponses biologiques chez deux espèces de dreissenidés dans un contexte de biosurveillance active d'une rivière urbaine, l'Orne

International audienceLes bivalves sont des organismes sentinelles utilisés en tant qu'indicateurs de la présence et/ou de la toxicité des contaminants dans des contextes d'expositions d'origine industrielle, agricole et/ou urbaine. L'objectif de nos travaux est d'évaluer et de caractériser les réponses biologiques (biomarqueurs) chez deux espèces de dreissènes (Dreissena polymorpha et Dreissena r. bugensis) lors d'opérations de biosurveillance active. Dans ce contexte, les dreissènes ont été encagées dans une rivière sidérurgique lorraine empreinte d’un lourd passé industriel, l'Orne. A la fin du XIXème siècle, le développement des activités sidérurgiques autour de cette rivière s’est accompagné de la construction de trois barrages, devenus obsolètes aujourd'hui. L’effacement de ces barrages a débuté en 2019 avec l’ouverture des vannes pour deux d'entre eux, engendrant de profonds remaniements du lit et modifiant l'hydrologie. Ces modifications hydromorphologiques associées à des épisodes de crues entraînent un risque accru de remise en suspension/circulation des sédiments contaminés qui ont été accumulés pendant les phases d'activité industrielle. Afin d'étudier l'impact potentiel de la remise en suspension des sédiments contaminés sur le biote, des biomarqueurs ont été mesurés dans les glandes digestives de dreissènes encagées dans l’Orne pendant deux crues hivernales successives. Les biomarqueurs choisis interviennent dans la gestion énergétique (activité de la Cytochrome c oxydase COX, de la chaine mitochondriale -Electron transport system- ETS et de la Lactate déshydrogénase LDH, et concentrations en Triglycérides TRI), dans la défense anti-toxique et anti-oxydante (activité de la Glutathion-S-Transférase GST, de la Glutathion Peroxydase GPx et de la Superoxyde Dismutase SOD, et Capacité antioxydante -Total Antioxidant Capacity- TAC,) et dans la survenue d'effets toxiques (activité de la Caspase 3 CSP et concentrations en peroxydes lipidiques LOOH). Les premiers résultats montrent que les deux espèces de dreissènes présentent des profils de réponse distincts. En effet, Dreissena polymorpha semble activer ses défenses anti-oxydantes au détriment de ses réserves énergétiques (TRI), ce qui lui permet néanmoins de limiter les effets toxiques en maintenant des niveaux faibles de peroxydes lipidiques (LOOH). A l'opposé, Dreissena r. bugensis préserve ses réserves en maintenant des niveaux de défense plus faibles, ce qui engendre en contrepartie une augmentation de la peroxydation lipidique. Concernant la question de l'impact de la crue sur les réponses biologiques, les résultats n'ont pas révélé de signaux de stress marqué suite à l'exposition. Finalement, cette approche multi-biomarqueurs nous a permis de caractériser les profils de réponses des dreissènes ainsi que de déterminer le caractère perturbé de certains sites. L’utilisation des biomarqueurs est de plus en plus recommandée dans les programmes de biosurveillance des cours d’eau. En effet, ces outils permettent une évaluation précoce et rapide de l’état du compartiment biologique à un niveau individuel et ils s’avèrent complémentaires des approches actuellement utilisées dans le cadre des suivis de l’état des masses d’eau imposés par la Directive Cadre sur l'Eau (DCE, 2000/60/CE)

Comparaison des réponses biologiques chez deux espèces de dreissenidés dans un contexte de biosurveillance active d'une rivière urbaine, l'Orne

International audienceLes bivalves sont des organismes sentinelles utilisés en tant qu'indicateurs de la présence et/ou de la toxicité des contaminants dans des contextes d'expositions d'origine industrielle, agricole et/ou urbaine. L'objectif de nos travaux est d'évaluer et de caractériser les réponses biologiques (biomarqueurs) chez deux espèces de dreissènes (Dreissena polymorpha et Dreissena r. bugensis) lors d'opérations de biosurveillance active. Dans ce contexte, les dreissènes ont été encagées dans une rivière sidérurgique lorraine empreinte d’un lourd passé industriel, l'Orne. A la fin du XIXème siècle, le développement des activités sidérurgiques autour de cette rivière s’est accompagné de la construction de trois barrages, devenus obsolètes aujourd'hui. L’effacement de ces barrages a débuté en 2019 avec l’ouverture des vannes pour deux d'entre eux, engendrant de profonds remaniements du lit et modifiant l'hydrologie. Ces modifications hydromorphologiques associées à des épisodes de crues entraînent un risque accru de remise en suspension/circulation des sédiments contaminés qui ont été accumulés pendant les phases d'activité industrielle. Afin d'étudier l'impact potentiel de la remise en suspension des sédiments contaminés sur le biote, des biomarqueurs ont été mesurés dans les glandes digestives de dreissènes encagées dans l’Orne pendant deux crues hivernales successives. Les biomarqueurs choisis interviennent dans la gestion énergétique (activité de la Cytochrome c oxydase COX, de la chaine mitochondriale -Electron transport system- ETS et de la Lactate déshydrogénase LDH, et concentrations en Triglycérides TRI), dans la défense anti-toxique et anti-oxydante (activité de la Glutathion-S-Transférase GST, de la Glutathion Peroxydase GPx et de la Superoxyde Dismutase SOD, et Capacité antioxydante -Total Antioxidant Capacity- TAC,) et dans la survenue d'effets toxiques (activité de la Caspase 3 CSP et concentrations en peroxydes lipidiques LOOH). Les premiers résultats montrent que les deux espèces de dreissènes présentent des profils de réponse distincts. En effet, Dreissena polymorpha semble activer ses défenses anti-oxydantes au détriment de ses réserves énergétiques (TRI), ce qui lui permet néanmoins de limiter les effets toxiques en maintenant des niveaux faibles de peroxydes lipidiques (LOOH). A l'opposé, Dreissena r. bugensis préserve ses réserves en maintenant des niveaux de défense plus faibles, ce qui engendre en contrepartie une augmentation de la peroxydation lipidique. Concernant la question de l'impact de la crue sur les réponses biologiques, les résultats n'ont pas révélé de signaux de stress marqué suite à l'exposition. Finalement, cette approche multi-biomarqueurs nous a permis de caractériser les profils de réponses des dreissènes ainsi que de déterminer le caractère perturbé de certains sites. L’utilisation des biomarqueurs est de plus en plus recommandée dans les programmes de biosurveillance des cours d’eau. En effet, ces outils permettent une évaluation précoce et rapide de l’état du compartiment biologique à un niveau individuel et ils s’avèrent complémentaires des approches actuellement utilisées dans le cadre des suivis de l’état des masses d’eau imposés par la Directive Cadre sur l'Eau (DCE, 2000/60/CE)

Multi-locus sequence typing provides epidemiological insights for diseased sharks infected with fungi belonging to the Fusarium solani species complex

International audienceFusarium spp. are saprobic moulds that are responsible for severe opportunistic infections in humans and animals. However, we need epidemiological tools to reliably trace the circulation of such fungal strains within medical or veterinary facilities, to recognize environmental contaminations that might lead to infection and to improve our understanding of factors responsible for the onset of outbreaks. In this study, we used molecular genotyping to investigate clustered cases of Fusarium solani species complex (FSSC) infection that occurred in eight Sphyrnidae sharks under managed care at a public aquarium. Genetic relationships between fungal strains were determined by multi-locus sequence typing (MLST) analysis based on DNA sequencing at five loci, followed by comparison with sequences of 50 epidemiologically unrelated FSSC strains. Our geno-typing approach revealed that F. keratoplasticum and F. solani haplotype 9x were most commonly isolated. In one case, the infection proved to be with another Hypocrealian rare opportunistic pathogen Metarhizium robertsii. Twice, sharks proved to be infected C Th