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result(s) for
"Daou, Laurent"
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The measurement and quantification of generalized gradients of soil fertility relevant to plant community ecology
by
Daou, Laurent
,
Shipley, Bill
in
Arabidopsis thaliana
,
Community ecology
,
Ecological monitoring
2019
We propose an operational definition of soil “fertility” that is applicable to plant community ecology and develop a method of measuring and quantifying it, using structural equations modeling, that is generalizable to soils in different regions whose fertility has different causes. To do this, we used structural equation modeling (SEM). The measurement submodel predicts the latent “generalized fertility,” F
G, of a soil using four indicator variables: the relative growth rates of Festuca rubra, Trifolium pratense, Triticum aestivum, and Arabidopsis thaliana. The direct causes of F
G in this study were the supply rates of NO3
− , P, and K as well as three indirect causes consisting of three physical soil properties, but these can change between studies. The model was calibrated using 76 grassland soils from southern Quebec, Canada and independently tested using aboveground net primary productivity (NPP) of the natural vegetation over two growing seasons. Both the measurement submodel and the full SEM fit the data well. The F
G values predicted 51% of the variance in NPP and were a better predictor than any other single variable, including the actual nutrient flux rates. Furthermore, this model can be applied to grassland soils anywhere because of its modular nature in which the causes and effects of soil fertility are clearly separated.
Journal Article
Simplifying the protocol for the quantification of generalized soil fertility gradients in grassland community ecology
2020
Aims
A new method, based on the latent variable measurement model, was recently developed to quantify generalised soil fertility (F
G
) in grassland ecosystems; i.e. the productive capacity of a soil at a multispecific scale when non-soil variables are held constant. To predict F
G
values, this method uses the relative growth rates (RGR) of
Festuca rubra, Trifolium pratense, Triticum aestivum
and
Arabidopsis thaliana
grown in intact soil.
We investigated three simplifications of this method; namely, (i) the use of sieved soil instead of intact cores, (ii) the use of a single measure of biomass production instead of RGR and (iii), a combination of these two modifications.
Methods
Using 26 grassland soils from southern Quebec (Canada), F
G
values were predicted for each method and compared using Pearson correlation coefficients. We also evaluated the performances of these different F
G
values, as well as measures of NO
3
−
, P and K in predicting aerial net primary production (NPP) of the vegetation in these sites in a common non-soil environment.
Result
The four methods had comparable and very consistent F
G
values and, although they were not numerically equivalent, they were equivalent in predicting natural NPP of plant communities, and these predictions were better than the direct measures of NO
3
−
, K and P flux rates as measured by Plant Root Simulator probes.
Conclusions
Therefore, any of these methods could be used to assess the generalized fertility.
Journal Article
Quantifying the relationship linking the community‐weighted means of plant traits and soil fertility
by
Daou, Laurent
,
Garnier, Éric
,
Shipley, Bill
in
Biodiversity and Ecology
,
biomass
,
Community‐weighted functional traits
2021
Is it possible to generalize relationships between certain plant traits and soil fertility? In particular, are there quantitative relationships between community-weighted mean (CWM) trait values of leaf dry-matter content (LDMC), specific leaf area (SLA), plant height, and Grime’s competitor-stress tolerator-ruderal (CSR) strategy scores and the generalized soil fertility, FG (i.e., the capacity of a soil to produce biomass when all nonsoil variables are held constant) that are generalizable across different species assemblages and geographical areas? We assessed FG in 21 sites in southern Quebec and 7 sites in southern France using a previously published method based on structural equation modeling. We then determined the CWM values of LDMC, SLA, plant height, and CSR scores in the 21 Quebec sites to obtain quantitative relationships between FG and these CWM traits. Using these relationships, we independently tested the generality of the trait–fertility relationships using data from French sites. The relationships between FG and the CWM traits were nonlinear, but displayed the expected qualitative trends as reported in the literature. In particular, the S score and CWM LDMC decreased with increasing soil fertility, and the R score and CWM SLA increased. CWM traits were more strongly correlated to measures of FG (r2 up to 0.48) than to measures of other soil characteristics (r2 up to 0.17 for nitrogen flux). Importantly, the independently tested French FG–trait relationships showed no significant deviations from these quantitative relationships. Further investigation is necessary to confirm if the same trend applies to other regions and or ecosystems.
Journal Article
Synthesis of FAU-Type Zeolite Membranes with Antimicrobial Activity
by
Michelin, Laure
,
Josien, Ludovic
,
Dutournie, Patrick
in
Adsorption
,
Anti-Bacterial Agents - chemical synthesis
,
Anti-Bacterial Agents - chemistry
2020
In this study, a layer of a pure and dense phase of FAU-type zeolite was synthesized directly on the surface of α-Al2O3 plane macroporous support. Before hydrothermal synthesis, a step of cleaning of the support by an anionic detergent was performed, a roughness surface is created, allowing the anchoring of the zeolite nuclei and then their growth, favoring in this sense the formation of a homogeneous zeolite layer. The obtained membranes were fully characterized using X-ray diffraction analysis (XRD), nitrogen sorption, scanning electron microscopy (SEM), and mercury porosimetry. After 24 h of thermal treatment at 75 °C, a homogeneous zeolite layer composed of bipyramidal crystals of FAU-type zeolite is obtained with a thickness of about 2.5 µm. No obvious defects or cracks can be observed. It was found that the increase in heating temperature could lead to the appearance of an impurity phase, GIS-type zeolite. Then the ideal zeolite membrane was exchanged with Ag+ or Zn2+ cations to studies their antimicrobial properties. Zeolites membranes exchanged with Ag+ showed an agar-diffusive bactericidal activity against gram negative Escherichia coli (E. coli) bacteria. Zn2+ exchanged zeolite membrane presented a bacteriostatic activity that is less diffusive in agar. As expected, non-exchanged zeolite membrane (in its Na+ form) have no effect on bacterial activity. This process is particularly interesting for the synthesis of a good quality FAU-type zeolite membranes with antimicrobial properties.
Journal Article
Did subduction in the Western Mediterranean drive Neogene alpine dynamics? Insights from analogue modeling
2024
In the Western Alps, a first Late Cretaceous to Eocene \"Pyrenean-Provençal\" compressive phase accommodating N-S shortening resulting from the convergence between Africa and Eurasia is classically described. It is followed by the Neogene \"Alpine phase\" accommodating E-W shortening. Since this major tectonic change is not explained by a modification of the global Africa-Eurasia convergence, it should be explained instead by more local causes, possibly by the subduction of the Ligurian Ocean that initiated in the Oligocene beneath the European and Iberian plates. In this paper, we present analogue models simulating the Neogene evolution of this subduction zone, in order to understand how it impacted the regional tectonics. Although models do not include the lithospheric plate overriding the subduction zone, their surface deformations share many similarities with the Neogene tectonics of Western Europe and Iberia. We observe that the tectonic evolution is largely controlled by the roll-back of the slab, that occurred much faster than the Africa-Eurasia convergence. Models reproduce the opening of the Western Mediterranean Basins and the dispersion of the AlKaPeCa continental fragments (Alboran, Kabylian, Peloritan and Calabrian blocks). They also show that the subduction of the Ligurian Ocean favors the counterclockwise rotation of Adria. In more elaborated models, we introduced a pre-existing weakness along the Africa and Adria margins, to reproduce the break-off of the oceanic slab that followed the beginning of continental subduction both in Northern Africa and Adria. Slab break-off is followed by the exhumation of the subducted continent. We observe that the influence of subduction on the kinematics of Adria largely decreases following slab break-off. In the models, the total counterclockwise rotation of Adria varies between 7° and more than 30°, depending on the timing of slab break-off. Since the process of subduction modifies the displacement of Adria, it also impacts the tectonic evolution of surrounding regions, especially in the Alpine belt: Our models show that during slab-roll back and before the Ligurian slab break-off, the azimuth of convergence between Adria and Europe shifts from ∼N-S to ∼ENE-WSW. Hence, they suggest that the oceanic subduction in the Western Mediterranean may contribute to the \"Oligocene revolution\" described by Dumont et al. (2011), leading to E-W shortening in the Western Alps and to the activation of the Periadriatic right-lateral shear zones in the Central Alps. We conclude that the western Mediterranean region is a spectacular example showing how the tectonics of mountain ranges and plate boundaries may be controlled by distant subduction processes.
Journal Article
The Impact of Preventive Protocols on Oral Health Outcomes in Cancer Patients Undergoing Chemotherapy or Radiotherapy: A Systematic Review and Meta-Analysis
2025
Background/Objectives: Cancer patients undergoing chemotherapy (CT) or radiotherapy (RT) are at increased risk of oral complications. Preventive dental care has been proposed to mitigate these risks, yet its effectiveness is not sufficiently evaluated. This systematic review and meta-analysis aimed to assess the impact of preventive oral health interventions on key clinical outcomes in oncology patients. Methods: A systematic search of MEDLINE, Embase, and CENTRAL databases was conducted (March 2025), adhering to PRISMA guidelines with a PROSPERO-registered protocol (CRD 420251006799). Eligible studies included randomized trials, cohort studies, and pre–post intervention studies evaluating preventive dental care in patients receiving CT or RT. The outcomes included gingival index (GI), dental caries (DMFT), plaque levels, and periodontal health. Meta-analyses were performed on GI and DMFT outcomes using random-effects models. Results: Eleven studies were included in the qualitative synthesis and four in the meta-analyses. Preventive interventions, such as fluoride applications, oral hygiene education, and regular professional cleanings, were associated with stabilization or improvement of gingival health. The pooled estimate for GI showed no significant deterioration over time (MD = −0.05, 95% CI: −0.34 to 0.24, p = 0.72). For DMFT, a slight but significant increase was observed (MD = 1.07, 95% CI: 0.08 to 2.05, p = 0.03), suggesting a continued risk of caries despite intervention. Conclusions: Preventive dental care interventions appear to support the maintenance of gingival health in cancer patients undergoing CT or RT. However, despite these interventions, a slight increase in dental caries was still observed, indicating that preventive strategies may not fully eliminate the risk of caries. These findings highlight the importance of sustained and individualized oral health programs as part of comprehensive oncology care. Future studies using standardized protocols and longer follow-up periods are needed to better evaluate their long-term effectiveness across diverse cancer populations.
Journal Article
Rational Design and Characterisation of Novel Mono- and Bimetallic Antibacterial Linde Type A Zeolite Materials
by
Reicher, Chloé
,
Michelin, Laure
,
Josien, Ludovic
in
Aluminosilicates
,
Aluminum silicates
,
antibacterial properties
2022
The development of antimicrobial devices and surfaces requires the setup of suitable materials, able to store and release active principles. In this context, zeolites, which are microporous aluminosilicate minerals, hold great promise, since they are able to serve as a reservoir for metal-ions with antimicrobial properties. Here, we report on the preparation of Linde Type A zeolites, partially exchanged with combinations of metal-ions (Ag+, Cu2+, Zn2+) at different loadings (0.1–11.9 wt.%). We combine X-ray fluorescence, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction to monitor the metal-ion contents, distribution, and conservation of the zeolite structure after exchange. Then, we evaluate their antimicrobial activity, using agar dilution and optical-density monitoring of Escherichia coli cultures. The results indicate that silver-loaded materials are at least 70-fold more active than the copper-, zinc-, and non-exchanged ones. Moreover, zeolites loaded with lower Ag+ concentrations remain active down to 0.1 wt.%, and their activities are directly proportional to the total Ag content. Sequential exchanges with two metal ions (Ag+ and either Cu2+, Zn2+) display synergetic or antagonist effects, depending on the quantity of the second metal. Altogether, this work shows that, by combining analytical and quantitative methods, it is possible to fine-tune the composition of bi-metal-exchanged zeolites, in order to maximise their antimicrobial potential, opening new ways for the development of next-generation composite zeolite-containing antimicrobial materials, with potential applications for the design of dental or bone implants, as well as biomedical devices and pharmaceutical products.
Journal Article
Impact of CodY protein on metabolism, sporulation and virulence in Clostridioides difficile ribotype 027
by
Nandakumar, Madhumitha
,
Bouillaut, Laurent
,
Zhang, Keshan
in
Amino Acid Sequence
,
Amino acids
,
Analysis
2019
Toxin synthesis and endospore formation are two of the most critical factors that determine the outcome of infection by Clostridioides difficile. The two major toxins, TcdA and TcdB, are the principal factors causing damage to the host. Spores are the infectious form of C. difficile, permit survival of the bacterium during antibiotic treatment and are the predominant cell form that leads to recurrent infection. Toxin production and sporulation have their own specific mechanisms of regulation, but they share negative regulation by the global regulatory protein CodY. Determining the extent of such regulation and its detailed mechanism is important for understanding the linkage between two apparently independent biological phenomena and raises the possibility of creating new ways of limiting infection. The work described here shows that a codY null mutant of a hypervirulent (ribotype 027) strain is even more virulent than its parent in a mouse model of infection and that the mutant expresses most sporulation genes prematurely during exponential growth phase. Moreover, examining the expression patterns of mutants producing CodY proteins with different levels of residual activity revealed that expression of the toxin genes is dependent on total CodY inactivation, whereas most sporulation genes are turned on when CodY activity is only partially diminished. These results suggest that, in wild-type cells undergoing nutrient limitation, sporulation genes can be turned on before the toxin genes.
Journal Article
Dental Health in Children with Congenital Heart Defects: A Systematic Review and Meta-Analysis
by
Kharouf, Naji
,
Moussa, Carol
,
Bourgi, Rim
in
Bias
,
Collaboration
,
Complications and side effects
2024
Background: Oral health outcomes in children with Congenital Heart Defects (CHD) have significant implications. The aim of this systematic review and meta-analysis is to update the current understanding of oral health outcomes in children with CHD and compare caries prevalence between CHD children and healthy controls. Methods: All studies between 2014 and 2024 comparing oral health status between children with and without CHD were considered for inclusion. Studies had to use the DMF/dmf index (Decayed, Missing, Filled Teeth or Surface index), in permanent and deciduous teeth. Two separate meta-analyses were conducted: one analyzing DMFS scores and another focusing on dmft scores. Medline, Central, and Embase databases were screened. Twelve articles were included in the qualitative synthesis, and two studies were finally included in each quantitative synthesis. Results: Several studies identified significant differences in oral health outcomes, suggesting that children with CHD are at a higher risk of dental caries compared with healthy controls, particularly as they become older. However, the differences were not uniformly observed across all studies and age groups. Based on the meta-analysis, there was no statistically significant difference in either DMFS scores (MD: 0.07 [95% CI: −0.13, 0.27]; p = 0.48) or in dmft scores (MD: 1.39 [95% CI: −1.05, 3.83]; p = 0.26). Conclusions: This systematic review and meta-analysis highlight a possible increased risk of dental caries in children with CHD, although results were not statistically significant and varied across studies. More standardized and rigorous studies are required to provide clearer insights into oral health outcomes for this population.
Journal Article
Fungal Treatment for the Valorization of Technical Soda Lignin
2021
Technical lignins produced as a by-product in biorefinery processes represent a potential source of renewable carbon. In consideration of the possibilities of the industrial transformation of this substrate into various valuable bio-based molecules, the biological deconstruction of a technical soda lignin by filamentous fungi was investigated. The ability of three basidiomycetes (Polyporus brumalis, Pycnoporus sanguineus and Leiotrametes menziesii) to modify this material, the resultant structural and chemical changes, and the secreted proteins during growth on this substrate were investigated. The three fungi could grow on the technical lignin alone, and the growth rate increased when the media were supplemented with glucose or maltose. The proteomic analysis of the culture supernatants after three days of growth revealed the secretion of numerous Carbohydrate-Active Enzymes (CAZymes). The secretomic profiles varied widely between the strains and the presence of technical lignin alone triggered the early secretion of many lignin-acting oxidoreductases. The secretomes were notably rich in glycoside hydrolases and H2O2-producing auxiliary activity enzymes with copper radical oxidases being induced on lignin for all strains. The lignin treatment by fungi modified both the soluble and insoluble lignin fractions. A significant decrease in the amount of soluble higher molar mass compounds was observed in the case of P. sanguineus. This strain was also responsible for the modification of the lower molar mass compounds of the lignin insoluble fraction and a 40% decrease in the thioacidolysis yield. The similarity in the activities of P. sanguineus and P. brumalis in modifying the functional groups of the technical lignin were observed, the results suggest that the lignin has undergone structural changes, or at least changes in its composition, and pave the route for the utilization of filamentous fungi to functionalize technical lignins and produce the enzymes of interest for biorefinery applications.
Journal Article