Multiple factors affecting Ixodes ricinus ticks and associated pathogens in European temperate ecosystems (northeastern France).

In Europe, the main vector of tick-borne zoonoses is Ixodes ricinus, which has three life stages. During their development cycle, ticks take three separate blood meals from a wide variety of vertebrate hosts, during which they can acquire and transmit human pathogens such as Borrelia burgdorferi sensu lato, the causative agent of Lyme borreliosis. In this study conducted in Northeastern France, we studied the importance of soil type, land use, forest stand type, and temporal dynamics on the abundance of ticks and their associated pathogens. Negative binomial regression modeling of the results indicated that limestone-based soils were more favorable to ticks than sandstone-based soils. The highest tick abundance was observed in forests, particularly among coniferous and mixed stands. We identified an effect of habitat time dynamics in forests and in wetlands: recent forests and current wetlands supported more ticks than stable forests and former wetlands, respectively. We observed a close association between tick abundance and the abundance of Cervidae, Leporidae, and birds. The tick-borne pathogens responsible for Lyme borreliosis, anaplasmosis, and hard tick relapsing fever showed specific habitat preferences and associations with specific animal families. Machine learning algorithms identified soil related variables as the best predictors of tick and pathogen abundance.

Photodegradation of disposable polypropylene face masks: Physicochemical properties of debris and implications for the toxicity of mask-carried river biofilms.

COVID-19 outbreak led to a massive dissemination of protective polypropylene (PP) face masks in the environment, posing a new environmental risk amplified by mask photodegradation and fragmentation. Masks are made up of a several kilometres long-network of fibres with diameter from a few microns to around 20 µm. After photodegradation, these fibres disintegrate, producing water dispersible debris. Electrokinetics and particle stability observations support that photodegradation increases/decreases the charge/hydrophobicity of released colloidal fragments. This change in hydrophobicity is related to the production of UV-induced carbonyl and hydroxyl reactive groups detectable after a few days of exposure. Helical content, surface roughness and specific surface area of mask fibres are not significantly impacted by photodegradation. Fragmentation of fibres makes apparent, at the newly formed surfaces, otherwise-buried additives like TiO2 nanoparticles and various organic components. Mortality of gammarids is found to increase significantly over time when fed with 3 days-UV aged masks that carry biofilms grown in river, which is due to a decreased abundance of microphytes therein. In contrast, bacteria abundance and microbial community composition remain unchanged regardless of mask degradation. Overall, this work reports physicochemical properties of pristine and photodegraded masks, and ecosystemic functions and ecotoxicity of freshwater biofilms they can carry.

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

Luminescent 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.

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.

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

Whole-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 non-specific 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.

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.

The 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.

Protozoans in subgingival biofilm: clinical and bacterial associated factors and impact of scaling and root planing treatment.

Objective: In patients with periodontitis, identification of protozoans and evaluation of some bacteria and clinical parameters associated and assessment of scaling and root planing (SRP) impact on their detection. Methods: Before and after SRP, subgingival microbiota was collected in two pathological and one healthy site from 30 periodontitis patients. One healthy site from 30 control patients was also sampled. The usual clinical periodontal parameters were recorded; microbial detection was determined by PCR hybridization system for bacteria and qPCR for protozoans. Results: In periodontitis group, Trichomonas tenax and two subtypes of Entamoeba gingivalis (ST1 and a variant ST2) were detected in respectively 33.3%, 70% and 18.3% of pathological samples, and in 6.7%, 10% and 3.3% healthy samples. In control group, ST1 alone was found in 3.3% of individuals. ST1 was associated with Gingival Index, Clinical Attachment Level (p ≤ 0.03) and with the total bacterial count (p = 0.02). T. tenax alone was associated with P. gingivalis, T. denticola and E. nodatum (p ≤ 0,02). After therapy, only T. tenax detection decreased significantly (p = 0.004) and no association between the protozoan elimination and improvement of pathological sites was found. Conclusions: Protozoans were associated with some clinical parameters and/or periodontopathogens in patients with periodontitis.

Development of a new TaqMan PCR assay for the detection of both Entamoeba gingivalis genotypes.

Entamoeba gingivalis is a parasitic protozoan found in the mouth of patients suffering from periodontitis, a widespread oral disease with an underestimated prevalence and major consequences on health. We present the development of the first TaqMan PCR assay targeting both E. gingivalis subtypes. This method has been evaluated on 50 samples from patients diagnosed with periodontitis in comparison with 2 different conventional PCRs, and a real-time SYBR Green PCR. Fifty percent of the samples were found positive for the E. gingivalis ST1 subtype with this new PCR, the SYBR Green PCR and one of the conventional PCRs. Among the 25 remaining samples, 12 (24%) were found positive for the E. gingivalis ST2 kamaktlii variant. This new TaqMan PCR could be used before and after periodontitis treatment to follow its efficacy and measure the parasite load in order to better understand the role of these parasites in oral diseases.

Protein N-glycosylation alteration and glycolysis inhibition both contribute to the antiproliferative action of 2-deoxyglucose in breast cancer cells.

PURPOSE: Cancer cells often elicit a higher glycolytic rate than normal cells, supporting the development of glycolysis inhibitors as therapeutic agents. 2-Deoxyglucose (2-DG) is used in this context due to its ability to compete with glucose. However, many studies do not take into account that 2-DG inhibits not only glycolysis but also N-glycosylation. Since there are limited publications on 2-DG mechanism of action in breast cancer, we studied its effects in breast cancer cell lines to determine the part played by glycolysis inhibition and N-linked glycosylation interference. METHODS AND RESULTS: 2-Deoxyglucose behaved as an anticancer agent with a similar efficiency on cell number decrease between the hormone-dependent MCF-7 and hormone-independent MDA-MB-231 breast cancer cells. It also interfered with the N-linked glycosylation process in both cell lines as illustrated by the migration profile of the lysosomal-associated membrane protein 2 and calumenin. These results are reinforced by the appearance of an abnormal Man7GlcNAc2 structure both on lipid-linked oligosaccharides and N-linked glycoproteins of 2-DG incubated MDA-MB-231 cells. Besides, 2-DG-induced a transient endoplasmic reticulum stress that was more sustained in MDA-MB-231 cells. Both changes were abrogated by mannose. 2-DG, even in the presence of mannose, decreased glycolysis in both cell lines. Mannose partially reversed the effects of 2-DG on cell numbers with N-linked glycosylation interference accounting for 37 and 47% of 2-DG anti-cancerous effects in MDA-MB-231 and MCF-7 cells, respectively. CONCLUSION: N-linked glycosylation interference and glycolysis disruption both contribute to the anticancer properties of 2-DG in breast cancer cells.

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

Fusarium 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 genotyping 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 with FSSC strains with the same MLST sequence type, supporting the hypothesis the hypothesis that common environmental populations of fungi existed for these sharks and would suggest the longtime persistence of the two clonal strains within the environment, perhaps in holding pools and life support systems of the aquarium. This study highlights how molecular tools like MLST can be used to investigate outbreaks of microbiological disease. This work reinforces the need for regular controls of water quality to reduce microbiological contamination due to waterborne microorganisms.

Δ2-Troglitazone promotes cytostatic rather than pro-apoptotic effects in breast cancer cells cultured in high serum conditions.

We have previously shown that Δ2-Troglitazone (Δ2-TGZ) displayed anticancer effects on breast cancer cell lines grown in low serum conditions (1% fetal calf serum (FCS)). The present study was performed in order to characterize the effects of Δ2-TGZ in high serum containing medium and to determine if starvation could influence the response of breast cancer cells to this compound, keeping in mind the potential interest for breast cancer therapy. We observed that in high serum conditions (10% FCS), a 48 h treatment with Δ2-TGZ induced a decrease in cell numbers in MDA-MB-231 and MCF-7 breast cancer cell lines. The IC50 values were higher than in low serum conditions. Furthermore, in contrast to our previous results obtained in 1% FCS conditions, we observed that in 10% FCS-containing medium, MCF-7 cells were more sensitive to Δ2-TGZ than MDA-MB-231 cells. Δ2-TGZ also induced endoplasmic reticulum (ER) stress mainly in MDA-MB-231 cells. Besides, in high serum conditions, Δ2-TGZ induced a G0/G1 cell cycle arrest, an inhibition of BrdU incorporation and a reduced level of cyclin D1. We observed a limited cleavage of PARP and a limited proportion of cells in sub-G1 phase. Thus, in high serum conditions, Δ2-TGZ displayed cytostatic effects rather than apoptosis as previously reported in 1% FCS-containing medium. Our results are in accordance with studies suggesting that serum starvation could potentiate the action of diverse anti-cancer agents.