Effect of the kinetics of temperature variation on Saccharomyces cereuisiae viability and permeability

AbstractThe variation rate of the temperature increase was found to have a great effect on the viability of Saccharomyces cerevisiae subjected to heat perturbations between 25°C and 50°C. A low intensity of the increase rate of temperature could maintain an important viability of the cells (about 34% of the initial population) with regard to the corresponding viability (about 1%) observed after a sudden step change for the same final temperature level of 50°C. A cell volume reduction more important (22% of the initial volume) has been observed in cells submitted to a heat shock than for the cells which have been submitted to a slow kinetic of temperature increase (9%). Such an observation allowed to propose a relation between the membrane permeability and the kinetics of temperature variation

Specific Gaseous Conditions Significantly Improve Lactobacillus casei and Escherichia coli Survival to Freeze Drying and Rehydration

 Background and objective: Presence of oxygen during production and rehydration of freeze-dried starters and probiotics can decrease viability of the bacteria. Indeed, removal of water from cells during freeze-drying can promote dysfunction in anti-oxidative mechanisms, resulting in oxidative stress by accumulation of reactive oxygen species. The aim of this study was to show how atmospheric or less oxidative gaseous conditions affect bacterial survival to freeze-drying and rehydration of two strains, including Lactobacillus casei, a widely used bacteria in biotechnology, and Escherichia coli, a laboratory model bacteria.Material and methods: Lactobacillus casei ATCC 334 and Escherichia coli K12 were freeze dried for 24h in 5% sucrose (m v-1). Two gaseous conditions (an oxygen-free gas and atmospheric air) were used during various steps of the process, including bacterial cultivation, mixing of the bacteria with the protectant and rehydration. Oxygen-free gas condition was obtained with an oxygen-free gas, composed of nitrogen, hydrogen and carbon dioxide (N2H2CO2)and an anaerobic chamber.Results and conclusion: Gaseous conditions included significant effects on bacterial survival rates (P<0.001 for Lactobacillus casei and Escherichia coli). Interestingly, for both bacteria, the optimal combination was atmospheric air during mixing of the bacteria with the lyoprotectant (P<0.001 for Lactobacillus casei and Escherichia coli) and N2H2CO2 during rehydration (P<0.001 for Lactobacillus casei and P<0.05 for Escherichia coli). Management of gaseous conditions during a freeze-drying process and rehydration (atmospheric air during mixing of the bacteria with lyoprotectant and oxygen-free gas during rehydration) enhances survival of the bacteria by preserving them from oxidative stress.Conflict of interest: The authors declare no conflict of interest

Surviving the heat:Heterogeneity of response in Saccharomyces cerevisiae provides insight into thermal damage to the membrane

Environmental heat stress impacts on the physiology and viability of microbial cells with concomitant implications for microbial activity and diversity. Previously, it has been demonstrated that gradual heating of Saccharomyces cerevisiae induces a degree of thermal resistance, whereas a heat shock results in a high level of cell death. Here, we show that the impact of exogenous nutrients on acquisition of thermal resistance differs between strains. Using single-cell methods, we demonstrate the extent of heterogeneity of the heat-stress response within populations of yeast cells and the presence of subpopulations that are reversibly damaged by heat stress. Such cells represent potential for recovery of entire populations once stresses are removed. The results show that plasma membrane permeability and potential are key factors involved in cell survival, but thermal resistance is not related to homeoviscous adaptation of the plasma membrane. These results have implications for growth and regrowth of populations experiencing environmental heat stress and our understanding of impacts at the level of the single cell. Given the important role of microbes in biofuel production and bioremediation, a thorough understanding of the impact of stress responses of populations and individuals is highly desirable

Effect of oxidoreduction potential and of gas bubbling on rheological properties and microstructure of acid skim milk gels acidified with glucono-delta-lactone

Milk oxidoreduction potential was modified using gases during the production of a model dairy product and its effect on gel setting was studied. Acidification by glucono-δ-lactone was used to examine the physicochemistry of gelation and to avoid variations due to microorganisms sensitive to oxidoreduction potential.Four conditions of oxidoreduction potential were appliedto milk: milk was gassed with air, nongassed, gassed with N2, or gassed with N2H2. The rheologicalproperties and microstructure of these gels were determined using viscoelasticimetry, measurement of whey separation, and confocal laser scanning microscopy. It appeared that a reducing environment led to less-aggregated proteins within the matrix and consequently decreased whey separation significantly. The use of gas to modify oxidoreduction potential is a possible way to improve the quality of dairy products

Molecular modeling and imaging of initial stages of cellulose fibril assembly: Evidence for a disordered intermediate stage

International audienceThe remarkable mechanical strength of cellulose reflects the arrangement of multiple β-1,4-linked glucan chains in a para-crystalline fibril. During plant cellulose biosynthesis, a multimeric cellulose synthesis complex (CSC) moves within the plane of the plasma membrane as many glucan chains are synthesized from the same end and in close proximity. Many questions remain about the mechanism of cellulose fibril assembly, for example must multiple catalytic subunits within one CSC polymerize cellulose at the same rate? How does the cellulose fibril bend to align horizontally with the cell wall? Here we used mathematical modeling to investigate the interactions between glucan chains immediately after extrusion on the plasma membrane surface. Molecular dynamics simulations on groups of six glucans, each originating from a position approximating its extrusion site, revealed initial formation of an uncrystallized aggregate of chains from which a protofibril arose spontaneously through a ratchet mechanism involving hydrogen bonds and van der Waals interactions between glucose monomers. Consistent with the predictions from the model, freeze-fracture transmission electron microscopy using improved methods revealed a hemispherical accumulation of material at points of origination of apparent cellulose fibrils on the external surface of the plasma membrane where rosette-type CSCs were also observed. Together the data support the possibility that a zone of uncrystallized chains on the plasma membrane surface buffers the predicted variable rates of cellulose polymerization from multiple catalytic subunits within the CSC and acts as a flexible hinge allowing the horizontal alignment of the crystalline cellulose fibrils relative to the cell wall

Trajectoires des travailleurs recevant un programme de retour au travail : étude exploratoire des discussions d’une équipe interdisciplinaire

Sujet : Cette étude exploratoire a pour objectif de décrire différents types de trajectoires de travailleurs présentant des troubles musculo-squelettiques pendant un programme de réadaptation. Les trajectoires sont tracées à partir des visions d’une équipe interdisciplinaire.Méthode : Le devis de recherche est une méthode de cas unique où l’unité d’analyse principale est une équipe interdisciplinaire. Cette équipe a discuté de la progression de 18 travailleurs, durant un programme de réadaptation. Les analyses des discussions ont été inspirées par la phénoménologie. Toutes les discussions de l’équipe ont été enregistrées et retranscrites. L’analyse de contenu a été effectuée par deux chercheurs. Résultats : Quatre types de trajectoires ont émergé : 1) trajectoires de retour au travail sans obstacle ; 2) trajectoires de retour au travail avec obstacles ; 3) trajectoires de non-retour au travail avec épisodes de progression et 4) trajectoires de non-retour au travail sans progression. Trois facteurs clefs ont émergé de ces analyses comme déterminant au processus de retour au travail : 1) la complaisance des travailleurs face au programme de réadaptation, 2) les différentes façons dont le travailleur aborde et vit la première exposition au travail et 3) la collaboration avec les différents partenaires. Les résultats de cette étude suggèrent aussi que l’absence de message unique entre les professionnels de la santé face au travailleur peut entraîner de la confusion et devenir un frein à la reprise des activités.Conclusions : Les résultats soulignent encore une fois la complexité pour les cliniciens de la prise en charge en réadaptation au travail de travailleurs en phase chronique. Cette intervention doit agir à la fois sur le travailleur et également sur les interactions entre les travailleurs et les différents partenaires concernés. Aussi, cette étude souligne le processus non linéaire de la réadaptation au travail pour des individus présentant des incapacités prolongées d’origine musculo-squelettique, tel que décrit par une équipe interdisciplinaire.Purpose : Based on the viewpoint of an interdisciplinary team, this exploratory study aimed to identify different types of trajectories followed by workers with musculoskeletal disorders and the factors contributing to them.Methods : The research design used a single-case study in which the main unit of analysis was an interdisciplinary work team. This team discussed eighteen workers’ progression during a work rehabilitation programme. Analytical methods were based on phenomenology. All team discussions were audiotaped and transcribed, and two researchers completed the content analysis.Results : Four types of trajectories emerged : (1) return-to-work trajectories without obstacles ; (2) return-to-work trajectories with obstacles ; (3) non-return-to-work trajectories with episodes of progression ; and (4) non-return-to-work trajectories without progression. Moreover, three outlines emerged from the data analysis : (1) the worker’s compliance with the programme ; (2) the way the worker coped with exposure to work ; and (3) stakeholder collaboration. The results of this study also suggested that the absence of a single consistent message among participating health professionals could create confusion for workers and pose a major impediment to the resumption of their activities.Conclusion : The results underscore, for clinicians, the complexity in managing this type of chronic work rehabilitation population, related to both the worker and the worker’s interactions with the stakeholders. Also, this study casts light on the non-linear work rehabilitation processes of individuals with prolonged disabilities of musculoskeletal origin, as described by an interdisciplinary team.Tema : Este estudio exploratorio se propone identificar diferentes tipos de trayectorias de trabajadores que presentan lesiones músculo-esqueléticas en el marco de un programa de readaptación. Las trayectorias se definen a partir de las visiones de un equipo interdisciplinar.Método : El método utilizado, llamado « devis de investigación » es un método basado en el estudio de casos y en el cual la unidad de análisis principal es un equipo interdisciplinar. En este caso, el equipo ha intercambiado opiniones acerca de la progresión de dieciocho trabajadores durante un programa de readaptación. El análisis de los intercambios ha seguido un enfoque fenomenológico. Todas las discusiones del equipo han sido grabadas y desgrabadas posteriormente. El análisis del contenido ha sido efectuado por dos investigadores.Resultados : Cuatro tipos de trayectorias han emergido : 1) trayectorias de reinsecion laboral sin obstaculos ; 2) Trayectorias de reinserción laboral con obstáculos ; 3) trayectorias sin reinserción laboral y con episodios de progresión ; y 4) trayectorias sin reinserción laboral y sin progresión. Tres factores clave han emergido de estos análisis en tanto determinates del proceso de reinserción laboral : 1) el hecho de que los trabajadores respeten el programa de readaptación, 2) las diferentes formas en las que el trabajador aborda y vive su primera exposición al trabajo, 3) la colaboracion con los diferentes compañeros de trabajo. Los resultados de este estudio sugieren tambien que la ausencia de unidad en los mensajes enviados por los profesionales de la salud al trabajador puede generar confusión y transformarse en un freno en el proceso de retorno a la actividad.Conclusiones : Los resultados obtenidos resaltan una vez más la complejidad que significa, desde un enfoque clínico, el hacerce cargo de la readaptación del trabajador en fase crónica. Esta intervención debe actuar a la vez sobre el trabajador y sobre las interacciones entre los trabajadores y las diferentes personas implicadas. Asimismo, este estudio subraya la no linealidad de la readaptación laboral para los individuos que presentan incapacidades prolongadas de origen musculoesquelético, tal como lo describe un equipo interdisciplinar

Surviving the heat:Heterogeneity of response in Saccharomyces cerevisiae provides insight into thermal damage to the membrane

International audienceEnvironmental heat stress impacts on the physiology and viability of microbial cells with concomitant implications for microbial activity and diversity. Previously, it has been demonstrated that gradual heating of Saccharomyces cerevisiae induces a degree of thermal resistance, whereas a heat shock results in a high level of cell death. Here, we show that the impact of exogenous nutrients on acquisition of thermal resistance differs between strains.Using single‐cell methods, we demonstrate the extent of heterogeneity of the heat‐stress response within populations of yeast cells and the presence of subpopulations that are reversibly damaged by heat stress. Such cells represent potential for recovery of entire populations once stresses are removed. The results show that plasma membrane permeability and potential are key factors involved in cell survival, but thermal resistance is not related to homeoviscous adaptation of the plasma membrane. These results have implications for growth and regrowth of populations experiencing environmental heat stress and our understanding of impacts at the level of the single cell. Given the important role of microbes in biofuel production and bioremediation, a thorough understanding of the impact of stress responses of populations and individuals is highly desirable

Dietary species richness as a measure of food biodiversity and nutritional quality of diets

Biodiversity is key for human and environmental health. Available dietary and ecological indicators are not designed to assess the intricate relationship between food biodiversity and diet quality. We applied biodiversity indicators to dietary intake data from and assessed associations with diet quality of women and young children. Data from 24-hour diet recalls (55% in the wet season) of n = 6,226 participants (34% women) in rural areas from seven lowand middle-income countries were analyzed. Mean adequacies of vitamin A, vitamin C, folate, calcium, iron, and zinc and diet diversity score (DDS) were used to assess diet quality. Associations of biodiversity indicators with nutrient adequacy were quantified using multilevel models, receiver operating characteristic curves, and test sensitivity and specificity. A total of 234 different species were consumed, of which < 30% were consumed in more than one country. Nine specieswere consumed in all countries and provided, on average, 61% of total energy intake and a significant contribution of micronutrients in the wet season. Compared with Simpson's index of diversity and functional diversity, species richness (SR) showed stronger associations and better diagnostic properties with micronutrient adequacy. For every additional species consumed, dietary nutrient adequacy increased by 0.03 (P < 0.001). Diets with higher nutrient adequacy were mostly obtained when both SR and DDS were maximal. Adding SR to the minimum cutoff for minimum diet diversity improved the ability to detect diets with higher micronutrient adequacy in women but not in children. Dietary SR is recommended as the most appropriate measure of food biodiversity in diets

Study and optimization of freeze-drying cycles of a model probiotic strain

[EN] This work is based on the experimental study of the freeze-drying process to understand the impact of numerous factors on the survival rates of a model probiotic strain of Lactobacillus casei type. With the aim to find out if cell density in the matrix and survival rates are linked, we have studied the location of the cells after freeze drying inside a porous matrix composed of a lactose basis with a polymer, the polyvinylpyrrolidone (PVP) in various amounts. The best survival rate were obtained at slow freezing rate for a formulation containing 5% (m/V) of lactose and 5% (m/V) of PVP.Verlhac, P.; Vessot-Crastes, S.; Degobert, G.; Cogné, C.; Andrieu, J.; Beney, L.; Gervais, P. (2018). Study and optimization of freeze-drying cycles of a model probiotic strain. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 635-642. https://doi.org/10.4995/IDS2018.2018.7400OCS63564

A novel CISD2 mutation associated with a classical Wolfram syndrome phenotype alters Ca2+ homeostasis and ER-mitochondria interactions.

Wolfram syndrome (WS) is a progressive neurodegenerative disease characterized by early-onset optic atrophy and diabetes mellitus, which can be associated with more extensive central nervous system and endocrine complications. The majority of patients harbour pathogenic WFS1 mutations, but recessive mutations in a second gene, CISD2, have been described in a small number of families with Wolfram syndrome type 2 (WFS2). The defining diagnostic criteria for WFS2 also consist of optic atrophy and diabetes mellitus, but unlike WFS1, this phenotypic subgroup has been associated with peptic ulcer disease and an increased bleeding tendency. Here, we report on a novel homozygous CISD2 mutation (c.215A > G; p.Asn72Ser) in a Moroccan patient with an overlapping phenotype suggesting that Wolfram syndrome type 1 and type 2 form a continuous clinical spectrum with genetic heterogeneity. The present study provides strong evidence that this particular CISD2 mutation disturbs cellular Ca2+ homeostasis with enhanced Ca2+ flux from the ER to mitochondria and cytosolic Ca2+ abnormalities in patient-derived fibroblasts. This Ca2+ dysregulation was associated with increased ER-mitochondria contact, a swollen ER lumen and a hyperfused mitochondrial network in the absence of overt ER stress. Although there was no marked alteration in mitochondrial bioenergetics under basal conditions, culture of patient-derived fibroblasts in glucose-free galactose medium revealed a respiratory chain defect in complexes I and II, and a trend towards decreased ATP levels. Our results provide important novel insight into the potential disease mechanisms underlying the neurodegenerative consequences of CISD2 mutations and the subsequent development of multisystemic disease