0000000000002577
AUTHOR
Sébastien Dupont
showing 16 related works from this author
Unsaturated fatty acids from food and in the growth medium improve growth of Bacillus cereus under cold and anaerobic conditions.
2013
International audience; In a chemically defined medium and in Luria broth, cold strongly reduced maximal population density of Bacillus cereus ATCC 14579 in anaerobiosis and caused formation of filaments. In cooked spinach, maximal population density of B. cereus in anaerobiosis was the same at cold and optimal temperatures, with normal cell divisions. The lipid containing fraction of spinach, but not the hydrophilic fraction, restored growth of B. cereus under cold and anaerobiosis when added to the chemically defined medium. This fraction was rich in unsaturated, low melting point fatty acids. Addition of phosphatidylcholine containing unsaturated, low melting point, fatty acids similarly…
Use of Gases in Microorganism Preservation Processes
2019
International audience
Management of Listeria monocytogenes on Surfaces via Relative Air Humidity: Key Role of Cell Envelope
2021
International audience; Although relative air humidity (RH) strongly influences microbial survival, its use for fighting surface pathogens in the food industry has been inadequately considered. We asked whether RH control could destroy Listeria monocytogenes EGDe by envelope damage. The impact of dehydration in phosphate-buffered saline (PBS) at 75%, 68%, 43% and 11% RH on the bacterial envelope was investigated using flow cytometry and atomic force microscopy. Changes after rehydration in the protein secondary structure and peptidoglycan were investigated by infrared spectroscopy. Complementary cultivability measurements were performed by running dehydration–rehydration with combinations o…
Nature of sterols affects plasma membrane behavior and yeast survival during dehydration.
2011
International audience; The plasma membrane (PM) is a main site of injury during osmotic perturbation. Sterols, major lipids of the PM structure in eukaryotes, are thought to play a role in ensuring the stability of the lipid bilayer during physicochemical perturbations. Here, we investigated the relationship between the nature of PM sterols and resistance of the yeast Saccharomyces cerevisiae to hyperosmotic treatment. We compared the responses to osmotic dehydration (viability, sterol quantification, ultrastructure, cell volume, and membrane permeability) in the wild-type (WT) strain and the ergosterol mutant erg6Δ strain. Our main results suggest that the nature of membrane sterols gover…
Modulation of lipid-induced ER stress by fatty acid shape.
2011
IF : 5,709; International audience; Exposure of pancreatic β cells to long-chain saturated fatty acids (SFA) induces a so-called endoplasmic reticulum (ER) stress that can ultimately lead to cell death. This process is believed to participate in insulin deficiency associated with type 2 diabetes, via a decrease in β-cell mass. By contrast, some unsaturated fatty acid species appear less toxic to the cells and can even alleviate SFA-induced ER stress. In the present study, we took advantage of a simple yeast-based model, which brings together most of the trademarks of lipotoxicity in human cells, to screen fatty acids of various structures for their capacity to counter ER stress. Here we dem…
Antioxidant Properties of Ergosterol and Its Role in Yeast Resistance to Oxidation
2021
International audience; Although the functions and structural roles of sterols have been the subject of numerous studies, the reasons for the diversity of sterols in the different eukaryotic kingdoms remain unclear. It is thought that the specificity of sterols is linked to unidentified supplementary functions that could enable organisms to be better adapted to their environment. Ergosterol is accumulated by late branching fungi that encounter oxidative perturbations in their interfacial habitats. Here, we investigated the antioxidant properties of ergosterol using in vivo, in vitro, and in silico approaches. The results showed that ergosterol is involved in yeast resistance to tert-butyl h…
Conservation à long terme de systèmes biologiques viables et fonctionnels
2013
National audience; La congélation et la déshydratation permettent la conservation de systèmes biologiques sur de longues périodes par le ralentissement des réactions de dégradation cellulaire. Ces opérations impliquent des transferts de chaleur et de masse pouvant conduire à l'altération des structures cellulaires. La maîtrise de la cinétique de ces transferts, associée à l'utilisation de différents protectants cellulaires, permet la mise en place de protocoles de congélation et de déshydratation spécifiques en fonction du système biologique à conserver.
Lateral reorganization of plasma membrane is involved in the yeast resistance to severe dehydration
2010
International audience; In this study, we investigated the kinetic and the magnitude of dehydrations on yeast plasma membrane (PM) modifications because this parameter is crucial to cell survival. Functional (permeability) and structural (morphology, ultrastructure, and distribution of the protein Sur7-GFP contained in sterol-rich membrane microdomains) PM modifications were investigated by confocal and electron microscopy after progressive (non-lethal) and rapid (lethal) hyperosmotic perturbations. Rapid cell dehydration induced the formation of many PM invaginations followed by membrane internalization of low sterol content PM regions with time. Permeabilization of the plasma membrane occ…
Ergosterol biosynthesis: a fungal pathway for life on land?
2012
International audience; Sterols, essential lipids of most eukaryotic cells, ensure important structural and signaling functions. The selection pressure that has led to different dominant sterols in the three eukaryotic kingdoms remains unknown. Here, we investigated the influence of the progression in the different steps of the ergosterol biosynthetic pathway (EBP) on the yeast resistance to transitions from aqueous to aerial media, typical perturbations of the higher fungi habitats. Five mutants of the EBP (ergΔ), accumulating different sterol intermediates in the EBP, and the wild-type (WT) strain were exposed to drying under atmospheric air or nitrogen and wetting. Results show that the …
Industrial production of dried yeast: plasma membrane as a survival indicator of air drying process
2011
International audience; Preservation of microorganisms by desiccationis a major industrial interest.However, study of cell survival mechanismsthat occur during desiccation is complex. In this work, the impact of the magnitude and the kinetics of dehydration on yeastsurvival wereevaluatedin either hyperosmotic liquid medium or a gaseous environment. Asame lethal magnitude of dehydration and a same lethal kinetic effect were found. As previously shown for osmotic stress, this work demonstrate that yeast survival after drying was also related to plasma membrane disorganization, suggesting a similar passive rearrangement of the membrane components.Hyperosmotic treatment in liquid medium represe…
Method for eliminating microorganisms present in and/or at the surface of a material to be decontaminated
2020
The present invention concems a method for eliminating microorganisms present in and/or at the surface of a material to be decontaminated comprising a step of irradiating said material to be decontaminated with radiation consisting of at least two light beams a1and a2 directed onto said material, the two light beams a1 and a2 respectively having a wavelength λ1 and λ2 of between 380 and 420nm.
Optimized tableting for extremely oxygen-sensitive probiotics using direct compression
2018
International audience; Faecalibacterium prausnitzii was previously recognized for its intestinal anti-inflammatory activities and it has been shown less abundant in patients with chronic intestinal diseases. However, the main problems encountered in the use of this interesting anaerobic microorganism are firstly its high sensitivity to the oxygen and secondly, its ability to reach the large intestine alive as targeted site. The aim of this study was to investigate the effect of direct compression on the viability of this probiotic strain after different compression pressure and storage using three different excipients (MCC, HPMC and HPMCP). The effect of compression process on cell viabili…
Anhydrobiosis: Inside yeast cells
2018
International audience; Under natural conditions yeast cells as well as other microorganisms are regularly subjected to the influence of severe drought, which leads to their serious dehydration. The dry seasons are then changed by rains and there is a restoration of normal water potential inside the cells. To survive such seasonal changes a lot of vegetative microbial cells, which belong to various genera and species, may be able to enter into a state of anhydrobiosis, in which their metabolism is temporarily and reversibly suspended or delayed. This evolutionarily developed adaptation to extreme conditions of the environment is widely used for practical goals - for conservation of microorg…
Collisional mechanism of ligand release by Bombyx mori JHBP, a member of the TULIP / Takeout family of lipid transporters.
2020
International audience; Juvenile hormones (JHs) regulate important processes in insects, such as postembryonic development and reproduction. In the hemolymph of Lepidoptera, these lipophilic sesquiterpenic hormones are transported from their site of synthesis to target tissues by high affinity carriers, the juvenile hormone binding proteins (JHBPs). Lepidopteran JHBPs belong to a recently uncovered, yet very ancient family of proteins sharing a common lipid fold (TULIP domain) and involved in shuttling various lipid ligands. One important, but poorly understood aspect of JHs action, is the mechanism of hormone transfer to or through the plasma membranes of target cells. Since many membrane-…
Sng1 associates with Nce102 to regulate the yeast Pkh–Ypk signalling module in response to sphingolipid status
2016
International audience; All cells are delimited by biological membranes, which are consequently a primary target of stress-induced damage. Cold alters membrane functionality by decreasing lipid fluidity and the activity of membrane proteins. In Saccharomyces cerevisiae, evidence links sphingolipid homeostasis and membrane phospholipid asymmetry to the activity of the Ypk1/2 proteins, the yeast orthologous of the mammalian SGK1-3 kinases. Their regulation is mediated by different protein kinases, including the PDK1 orthologous Pkh1/2p, and requires the function of protein effectors, among them Nce102p, a component of the sphingolipid sensor machinery. Nevertheless, the mechanisms and the act…
Involvement of the plasma membrane in saccharomyces cerevisiae resistance to hydric perturbations : key role of ergosterol
2011
Preservation of microorganisms of interest (ferments, probiotics) in dry form is widespread in the industry. However, the dehydration processes lead to variable survival rates according to the group, species and strain of microorganism considered, but also according to the type of process used (drying, freeze drying, freezing). The plasma membrane (PM), by its position between the intra-and extracellular environment, is a target of hydric perturbations. Changes in this structure during hydric stresses are described to be directly involved in microorganism death. Understanding of membrane responses occurring during a dehydration/rehydration cycle is essential to maximize the survival of micr…