Fungi

Résumé

vignette|La présence de sporophores en console du Polypore amadouvier sur le volis et la chandelle d'un hêtre montre que ce dernier a été attaqué par ce champignon nécrotrophe lignicole à l'origine de la pourriture blanche qui creuse le cœur de l'arbre qu'il parasite en le faisant mourir d'épuisement. La poursuite du développement de ce macromycète sur le volis entraîne une modification rapide de l'orientation de la « fructification » en croissance, afin de pouvoir projeter les spores fongiques dans les conditions optimales. vignette|Autre agent actif d'une pourriture du bois, l'Hypholome en touffes, champignon saprotrophe très commun. Les Fonges (), également appelés Mycètes (), sont un règne d'organismes eucaryotes appelés communément champignons. Ce règne est diversifié, regroupant des organismes microscopiques, invisibles à l'œil nu, microchampignons unicellulaires (levures) ou pluricellulaires (moisissures), jusqu'aux « champignons supérieurs » dotés le plus souvent d'un pied et

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https://fr.wikipedia.org/wiki/Fungi

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Hydrophilic nanocarriers, formed by electrostatic interaction between their oppositely charged components, are recognized as nanomaterials with an enormous potential as vectors in biomedical and pharmaceutical applications. However, comprehensive information about their fate in various biological environments is still lacking. In general, due to their size, nanoparticles are able to enter and transport molecules into cells via pathways forbidden for bigger structures of even identical chemical nature. Research under defined conditions aiming at a better understanding of nanoparticle-cell interactions is crucial for the development of safe and successful nanocarriers for biomedical and pharmaceutical applications. Nanogels produced by electrostatic interaction of two types of the polysaccharide chitosan and pentasodium triphosphate were the subject of the research of this thesis. Additional surface coating with sodium alginate conferred to the nanogels a negatively charged surface enabling sufficient stability under physiological and in vivo relevant conditions. Of particular interest was the comparison of the two chitosan types, the first one obtained from usual animal sources while the second one became newly available from fungal sources. Prerequisite for the comparison in terms of nanogel formation, stability, interaction with cells and potential applications was the detailed analysis and characterization of the chitosan samples. The identification of almost identical degree of deacetylation, very similar molar mass distribution and solution behavior, but a somewhat higher molar mass of the animal chitosan as the only difference, allowed for a direct comparison. The animal and fungal derived chitosan samples yielded similar nanogels in relation to formation, size distributions and zeta potential. The nanogels were spherical with a hydrodynamic diameter in the range of 450 nm and a zeta potential of approx. -65 mV. The physical characteristics of the nanogels were clearly influenced by the ionic strength and temperature of the suspension. High deformability of the nanogel network was demonstrated by filtration through pores much narrower than the gel diameter. Temperature cycles in the range of 4°C to 37°C proved reversibility of size and zeta potential. The nanogels were stable in both simulated in vivo environment and in conditioned cell culture media. Exposure of seven human cancerous and non-cancerous cell lines to the nanogels, to identify the influence on the cell metabolic activity, revealed cell-type, nanogel dosage and exposure time dependence. However, nanogels prepared from animal and fungal chitosan showed similar behavior in vitro in all cell lines tested. The results obtained so far confirm fungal derived chitosan as an alternative to the animal derived chitosan. Nanogels carrying model protein antigen cargoes were taken up by porcine monocyte-derived dendritic cells, and kinetic analysis using an auto-quenched protein revealed a time-dependent endocytic processing of the nanogel cargo. These in vitro analyses were elaborated with an in vivo murine immunization experiment. Nanogels carrying ovalbumin (OVA) induced a dose-dependent antibody response over 6 weeks post-vaccination. An effective memory response was induced in nanogel-OVA immunized mice following a 0.1 µg OVA boost injection. Nanogels were also prepared carrying recombinant vaccine antigen against Neospora caninum. These induced a protective immune response following both intranasal and intraperitoneal vaccination in mice challenged with the tachyzoite form of the parasite. Overall, the results obtained in the framework of this research extend the knowledge on chitosan-based nanogels intended as nanocarriers for biomedical/pharmaceutical applications and contribute to further development of effective nanogel-based delivery systems.

EPFL2011

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Despite recent advances in down-stream processing, production of microalgae remains substantially limited because of economical reasons. Harvesting and dewatering are the most energy-intensive processing steps in their production and contribute 20–30% of total operational cost. Bio-flocculation of microalgae by co-cultivation with filamentous fungi relies on the development of large structures that facilitate cost effective harvesting. A yet unknown filamentous fungus was isolated as a contaminant from a microalgal culture and identified as Isaria fumosorosea. Blastospores production was optimized in minimal medium and the development of pellets, possibly lichens, was followed when co-cultured with Chlorella sorokiniana under strict autotrophic conditions. Stable pellets (1–2 mm) formed rapidly at pH 7–8, clearing the medium of free algal cells. Biomass was harvested with large inexpensive filters, generating wet slurry suitable for hydrothermal gasification. Nutrient rich brine from the aqueous phase of hydrothermal gasification supported growth of the fungus and may increase the process sustainability.

Elsevier2015

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Evolution of longevity improves immunity in Drosophila

Bruno Lemaitre

Much has been learned about the genetics of aging from studies in model organisms, but still little is known about naturally occurring alleles that contribute to variation in longevity. For example, analysis of mutants and transgenes has identified insulin signaling as a major regulator of longevity, yet whether standing variation in this pathway underlies microevolutionary changes in lifespan and correlated fitness traits remains largely unclear. Here, we have analyzed the genomes of a set of Drosophila melanogaster lines that have been maintained under direct selection for postponed reproduction and indirect selection for longevity, relative to unselected control lines, for over 35 years. We identified many candidate loci shaped by selection for longevity and late-life fertility, but - contrary to expectation - we did not find overrepresentation of canonical longevity genes. Instead, we found an enrichment of immunity genes, particularly in the Toll pathway, suggesting that evolutionary changes in immune function might underpin - in part - the evolution of late-life fertility and longevity. To test whether this genomic signature is causative, we performed functional experiments. In contrast to control flies, long-lived flies tended to downregulate the expression of antimicrobial peptides upon infection with age yet survived fungal, bacterial, and viral infections significantly better, consistent with alleviated immunosenescence. To examine whether genes of the Toll pathway directly affect longevity, we employed conditional knockdown using in vivo RNAi. In adults, RNAi against the Toll receptor extended lifespan, whereas silencing the pathway antagonist cactus--causing immune hyperactivation - dramatically shortened lifespan. Together, our results suggest that genetic changes in the age-dependent regulation of immune homeostasis might contribute to the evolution of longer life.

JOHN WILEY & SONS LTD2018

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EPFL2011

Evolution of longevity improves immunity in Drosophila

Bruno Lemaitre

JOHN WILEY & SONS LTD2018