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Precision cut lung slices: a novel versatile tool to examine host-pathogen interaction in the chicken lung
No full textThe avian respiratory tract is a common entry route for many pathogens and an important delivery route for vaccination in the poultry industry. Immune responses in the avian lung have mostly been studied in vivo due to the lack of robust, relevant in vitro and ex vivo models mimicking the microenvironment. Precision-cut lung slices (PCLS) have the major advantages of maintaining the 3-dimensional architecture of the lung and includes heterogeneous cell populations. PCLS have been obtained from a number of mammalian species and from chicken embryos. However, as the embryonic lung is physiologically undifferentiated and immunologically immature, it is less suitable to examine complex host-pathogen interactions including antimicrobial responses. Here we prepared PCLS from immunologically mature chicken lungs, tested different culture conditions, and found that serum supplementation has a detrimental effect on the quality of PCLS. Viable cells in PCLS remained present for ≥ 40 days, as determined by viability assays and sustained motility of fluorescent mononuclear phagocytic cells. The PCLS were responsive to lipopolysaccharide stimulation, which induced the release of nitric oxide, IL-1β, type I interferons and IL-10. Mononuclear phagocytes within the tissue maintained phagocytic activity, with live cell imaging capturing interactions with latex beads and an avian pathogenic Escherichia coli strain. Finally, the PCLS were also shown to be permissive to infection with low pathogenic avian influenza viruses. Taken together, immunologically mature chicken PCLS provide a suitable model to simulate live organ responsiveness and cell dynamics, which can be readily exploited to examine host-pathogen interactions and inflammatory responses
Comparative Genomics and Phylogenetic Analyses Suggest Several Novel Species within Clavibacter sp. Including Non-Pathogenic Tomato-Associated Strains
No full textMembers of Clavibacter spp. are economically important bacterial plant pathogens infecting a set of diverse agricultural crops (e.g. alfalfa, corn, potato, tomato, and wheat). Tomato-associated Clavibacter spp. strains occupy a great portion of genetic diversity of the genus, and C. michiganensis sensu stricto (formerly C.michiganensis subsp. michiganensis) causing bacterial canker disease considered one of the destructive seed-borne agents of the crop worldwide. However, current taxonomic descriptions of the genus do not reflect the existing diversity of the strains, resulting in unsatisfactory consequences in quarantine surveys for the pathogens. In this study, we used all the available genome sequences of Clavibacter spp. strains − including the type strains of newly described subspecies − to provide a precise insight into the diversity of tomato-associated members of the genus, and further clarify taxonomic status of the strains using genotypic and phenotypic features. Results of phylogenetic analyses revealed the existence of nine hypothetical new species among the investigated strains. None of the three new subspecies (i.e. C. michiganensis subsp. californiensis, C. michiganensis subsp. chilensis and C. michiganensis subsp. phaseoli) is included within the tomato-pathogenic C. michiganensis sensu stricto lineage. Although comparative genomics revealed the lack of chp and tomA pathogenicity determinant gene clusters in the non-pathogenic strains, a number of pathogenicity related genes were noted to be present in all the strains regardless of their pathogenicity characteristics. Altogether, our results advocate a need for a formal taxonomic reconsideration of tomato-associated Clavibacter spp. strains to facilitate differentiation of the lineages in quarantine inspections
Effect of two agro-pedo-climatic zones, drying methods and pelleting processes on chemical composition of Manihot esculenta (sp.), Leucaena leucocephala and Cajanus cajan
No full textIn tropical and subtropical countries, livestock productivity may be affected by the availability of food resources and the high prevalence of gastrointestinal pathogenic nematodes. The classical method of control using anthelmintic drugs is becoming decreasingly efficient because of a generalised resistance of the gastrointestinal nematodes suppress (GIN) to most of the drugs. In small farms, protein-rich biomasses with significant amounts of condensed tannins (CT), which are known to have anthelminbtic properties, might be good candidates to produce nutraceuticals. This experiment was conducted to determine the feasibility of producing nutraceutical pellets from Manihot esculenta sp., Cajanus cajan and Leucaena leucocephala, considering the influence of agro-pedo-climatic conditions plant species and technological factors, such as drying and pelleting. The samples were harvested in two different agro-pedo-climatic zones and sundried under shelter (at 25 to 35°C) or in a ventilated oven (45°C) before pelleting. Chemical analysis on crude protein and condensed tannins were conducted. The chemical composition of the plants did not vary significantly with agro-pedo-climatic conditions. Sun-drying and oven-drying decreased the CT content of the plants. No effect of pelleting was recorded on crude protein and CT contents, except for C. cajan, for which a small decrease in CT content was observed. Protein-rich foliage types with CT contents above 50 g/kg of dry matter are potentially good candidates to produce nutraceutical pellets if they are dried using mild drying conditions, like sun-drying under shelter
Investigation of Genetic Relationships Between Hanseniaspora Species Found in Grape Musts Revealed Interspecific Hybrids With Dynamic Genome Structures
No full textHanseniaspora, a predominant yeast genus of grape musts, includes sister species recently reported as fast evolving. The aim of this study was to investigate the genetic relationships between the four most closely related species, at the population level. A multi-locus sequence typing strategy based on five markers was applied on 107 strains, confirming the clear delineation of species H. uvarum, H. opuntiae, H. guilliermondii, and H. pseudoguilliermondii. Huge variations were observed in the level of intraspecific nucleotide diversity, and differences in heterozygosity between species indicate different life styles. No clear population structure was detected based on geographical or substrate origins. Instead, H. guilliermondii strains clustered into two distinct groups, which may reflect a recent step toward speciation. Interspecific hybrids were detected between H. opuntiae and H. pseudoguilliermondii. Their characterization using flow cytometry, karyotypes and genome sequencing showed different genome structures in different ploidy contexts: allodiploids, allotriploids, and allotetraploids. Subculturing of an allotriploid strain revealed chromosome loss equivalent to one chromosome set, followed by an auto-diploidization event, whereas another auto-diploidized tetraploid showed a segmental duplication. Altogether, these results suggest that Hanseniaspora genomes are not only fast evolving but also highly dynamic
About biomass overyielding of mixed cultures in batch processes
No full textWe study mechanisms that can produce an increase of biomass production in batch processes when considering mixed cultures, compared to pure cultures. We show that growth thresholds or variable yields can produce 'overyielding', while this is not possible in the classical batch model with multiple species. We give sufficient conditions on the characteristics of the species to obtain overyielding, and illustrate these theoretical results with numerical simulations. This work provides new insights on species complementary in models of mixed cultures, without having to consider direct interactions terms between species as, for instance in the well known Generalized Lotka-Volterra model
Applicability of an unmedicated feeding program aimed to reduce the use of antimicrobials in nursery piglets: impact on performance and fecal microbiota
No full textThis study aimed to assess the impact of two different feeding programs, including or not antimicrobials, on gut microbiota development at early ages in commercial pigs. For this, 21-day-old weaned piglets were distributed into 12 pens (6 replicates with 26 pigs each) and fed ad libitum until fattening with: standard commercial formula with antibiotics and zinc oxide (2400 ppm) (AB), and alternative unmedicated feed formula (UN). Subsequently, the animals were moved to the fattening unit (F) receiving a common diet. Pigs were weighed, and feed consumption and diarrhea scores registered. Feces were collected on days 9 (pre-starter), 40 (starter) and 72 (fattening) post-weaning and microbial DNA extracted for 16S rDNA sequencing. Piglets fed UN diets had a worse feed efficiency (p < 0.05) than AB during nursery; however, UN pigs spent less time scouring after weaning (p = 0.098). The structure of fecal community evolved with the age of the animals (p = 0.001), and diet also showed to have a role, particularly in the starter period when UN microbiomes clustered apart from AB, resembling the ecosystems found in the fattening animals. Fibrolytic genera (Fibrobacter, Butyrivibrio, Christellansellaceae) were enriched in UN piglets whereas Lactobacillus characterized AB piglets (adjusted p < 0.05). Overall, this alternative feeding program could anticipate the gut development of piglets despite a lower feed efficiency compared to standard medicalized programs
Evaluation d’une stratégie de valorisation de biomasse en alicaments anthelminthiques pour les petits ruminants dans les systèmes polyculture élevage
No full textDans les pays tropicaux et subtropicaux, l’élevage des petits ruminants peut être entravé par la disponibilité en ressources alimentaires et la forte prévalence des nématodes gastro-intestinaux. L’utilisation d’anthelminthiques de synthèse a entrainé l’apparition de souches parasitaires résistantes à la plupart des molécules. Dans les systèmes polyculture élevage, la présence de biomasse végétale aux propriétés alicamentaires permet de proposer une alternative aux anthelminthiques chimiques. Ce travail de thèse a consisté à évaluer une stratégie de valorisation de biomasse en alicaments anthelminthiques en utilisant la granulation. La Guadeloupe a été choisie comme modèle d’étude et trois biomasses, riches en protéines et en tannins condensés ont été étudiées : Manihot esculenta, Cajanus cajan et Leucaena leucocephala. L’évaluation a consisté tout d’abord à étudier l’influence des conditions agro-pédo-climatiques, de l’espèce de la plante et de la granulation sur la composition chimique des granulés. Puis nous avons étudié la valeur protéique, les propriétés anthelminthiques et alicamentaires des granulés en combinant des approches in vitro et in vivo.
Les résultats ont montré que la composition des plantes en métabolites primaires et en tannins condensés dépendait essentiellement de l’espèce et non des conditions agro-pédo-climatiques. Un séchage solaire sous abri à température modérée (25 à 35°C) permet de préserver des concentrations en tannins condensés compatibles avec des propriétés anthelminthiques du granulé. La valeur nutritionnelle et alimentaire a été approchée par l’étude de la dégradabilité des protéines contenues dans les ressources, grâce à la méthode d’Ørskov. Globalement, les résultats montrent qu'il existe une grande variabilité dans la dégradabilité effective des protéines. La granulation est neutre ou a un effet favorable sur cette valeur protéique.
Les propriétés anthelminthiques d’extraits de tannins condensés provenant des granulés des trois plantes et de leur mélange ont été étudiées in vitro. Les résultats ont montré que les effets étaient variables en fonction des espèces. L’analyse HPLC des extraits montre que cette variabilité peut s’expliquer par des différences de composition en tannins condensés entre les espèces de plante. Les propriétés alicamentaires ont été étudiées en comparant les réponses animales (ingestion, digestion, croissance) et les indicateurs de santé (excrétion fécale d’oeufs, taux d’hématocrite, nombre d’éosinophiles) de chevreaux nourris par des rations mixtes composées de foin et des biomasses expérimentales. Les gains moyens quotidiens élevés des animaux et la réduction significative du nombre d’oeufs par g de fèces confirment l’activité alicamentaire des granulés. L’ensemble de nos résultats montre que le séchage solaire sous serre, suivi de la granulation des biomasses expérimentales permet de produire des granulés de bonne valeur alicamentaire et que cette dernière dépend essentiellement de l’espèce de plante choisie
Structural organization and behaviour of casein micelles fouling layer during crossflow filtration of milk at low temperature : A Small-Angle X-Ray Scattering (SAXS), osmotic stress and rheology study
No full textDuring filtration of skimmed milk, the casein micelles accumulate at the membrane surface and their presence has a crucial impact on the performances of the operation and on the products properties. Information is still scarce, especially at ‘low’ temperature (≈8-12°C), about how the casein micelles behave at the membrane surface and interact in such concentrated regimes. The aim of this work was to understand the structural organization and behavior of concentrated casein micelles accumulated at the membrane during crossflow filtration (concentration, sol-gel transition, cohesiveness and reversibility) with a focus on impact of temperature.
The strategy consisted in combining in-situ measurements by Small-Angle X-Ray Scattering coupled to crossflow filtration, with ex-situ characterization of concentrated dispersions of casein micelles using osmotic stress technique and rheology. Swelling-re-dispersion experiments were carried out to characterize the cohesiveness of micelles concentrates.
During in-situ filtration performed at constant pressure, increasing temperature (12, 25, 42°C) increased permeate flux (which was mainly attributed to the decrease of viscosity of permeate) and led to higher accumulation of casein micelles and a thicker deposit. The relaxation of pressure showed that casein micelles deposit was more cohesive at low temperature. With osmotic stress and rheology experiments, it was observed that compressibility (concentration reached at given osmotic pressure) and sol-gel transition concentration of casein micelles increased with the temperature increasing from 7 to 20°C. Moreover, swelling of casein micelles gels at 7°C resulted in lower redispersion rate as compared to the swelling at 20°C regardless of the gel formation temperature. It was also observed that casein micelles gels obtained at 7°C are more cohesive than those prepared at 20°C.
This work shows that carrying out filtration at low temperature led to a lower accumulation of casein micelle (lower compressibility of casein micelles), but to a higher cohesiveness of the accumulated micelles (lower sol/gel transition and swelling properties). These results were attributed to physico-chemical modifications of casein micelles (voluminosity, hydration) under temperature changes
Evidence and quantitative evaluation of tensile maturation strain in flax phloem through longitudinal splitting
No full textThe stems of flax (Linum usitatissimum L. cv. 'Mogilevsky') contain many gelatinous fibers in their phloem. These fibers are important for the mechanical stability of the plant as well as for industrial applications. Gelatinous fibers are known to have a motor function in the xylem of trees and in many plant organs. This function arises from the so-called maturation strain, i.e., the tendency of the gelatinous layer to shrink during fiber maturation, resulting in a state of residual tensile stress. However, the occurrence of tensile maturation strain in flax phloem fibers remains to be demonstrated, and its magnitude has never been evaluated. Here we present a novel method to highlight and quantify this strain. The method consists in splitting a stem segment longitudinally, and measuring the curvature of the half segments through their opening distance. By using a mechanical model, the maturation strain can be calculated from the curvature, the dimensions of the component tissues, and their elastic properties. The model is validated by the agreement between model predictions and observations. The splitting experiment provides qualitative evidence that flax phloem develops tensile stress during maturation, just as xylem gelatinous fibers do. Calculations enable quantitative estimation of the maturation strain. The magnitude of this strain for the material studied is, on average, -1.5%