1,720,985 research outputs found
Replication Data for: Invert emulsions alleviate biotic interactions in bacterial mixed culture
No full textThe large application potential of microbiotas has led to a great need for mixed culture methods. However, microbial interactions can compromise the maintenance of biodiversity during cultivation in a reactor. In particular, competition among species can lead to a strong disequilibrium in favor of the fittest microorganism. In this study, an invert emulsion system was designed by dispersing culture medium in a mixture of sunflower oil and the surfactant PGPR.
Granulomorphometric analysis was performed to investigate the effect of incubation and of the introduction of bacteria on the particle size distribution of invert emulsions.
Selected bacteria were propagated as single-strain cultures in order to assess the effect of invert emulsion on bacterial growth upon 24 h and 72 h timescales.
A two-strain antagonistic model was co-cultivated on a range of inoculum levels in order to inquire into the bacterial interaction alleviation properties of invert emulsions.
Finally, the effect of this cultivation system on the structure of bacterial communities was assessed by propagating a bacterial consortium consisting of six bacterial species. Metabarcoding analysis was then conducted by Illumina sequencing of 16S rRNA (v4) gene amplimers
Inhibition of Listeria monocytogenes in a cashew-based cheese analog model using two different Carnobacterium maltaromaticum strains
No full textThe present work assessed the anti-Listeria monocytogenes potential of two Carnobacterium maltaromaticum strains in liquid co-cultures and in model cheese analogs made with cashew nuts. These models were subjected to core and rind pH measurements as well as evaluation of their microbial diversity (bacteria and fungi) using amplicon sequencing, in the presence or absence of C. maltaromaticum. The minimum inhibitory concentrations (MICs) of the two candidate strains were assessed for nine antibiotics, and these MICs were then compared to the threshold values recommended by the European Food Safety Authority (EFSA)
Replication data for: Serial cultures in invert emulsion and monophase systems for microbial community shaping and propagation
No full textIn this study, bacterial communities derived from three different raw milks were serially propagated using two different culture systems, namely a monophasic culture system and an invert emulsion system. The resulting communities were characterized by enumeration and amplicon sequencing to assess the impact of the cultivation technique on their densities and structures in terms of alpha and beta diversity. Bacterial isolates were also identified using Sanger sequencing in order to evaluate the potential of the invert emulsion technique for bacterial enrichment and subsequent isolation
A selection process based on the robustness of anti-Listeria monocytogenes activity reveals two strains of Carnobacterium maltaromaticum with biopreservation properties in cheese
No full textInternational audienceBiopreservation is an approach consisting of using microorganisms as protective cultures and/or their metabolites to optimize the microbiological quality and shelf life of food by ensuring safety or reducing food waste. Biopreservation strain selection pipelines mainly focus on inhibition strength to identify strains of interest. However, in addition to inhibition strength, inhibition activity must be able to be expressed despite significant variations in food matrix properties. In this study, the anti-Listeria monocytogenes EGDelux properties of a collection of 77 Carnobacterium maltaromaticum strains were investigated by high throughput competition assays under varying conditions of co-culture inoculation level, time interval between inoculation with C. maltaromaticum and L. monocytogenes, pH, and NaCl, resulting in 1309 different combinations of C. maltaromaticum strains and culture conditions. This screening led to the selection of two candidate strains with potent and robust anti-L. monocytogenes activities. Deferred growth inhibition assays followed by halo measurements, and liquid co-culture followed by colony counting, revealed that these two strains exhibit a wide anti-Listeria spectrum. Challenge tests in Camembert and Saint-Nectaire cheese revealed both strains were able to inhibit a cocktail of five strains of L. monocytogenes with high potency and high reproducibility. These results highlight the importance of including the robustness criterion in addition to potency when designing a strain selection process for biopreservation applications
Propagation de communautés bactériennes : modelage, stabilisation et sélection pour la biopréservation
No full textRecent discoveries about microbial communities, or microbiota, have revealed considerable biotechnological potential in a variety of fields. They are considered essential to accelerate innovation in food production systems. However, existing processes are not adapted to the cultivation of microbiota. One major barrier to community propagation is competition between microorganisms, which can lead to an undesirable reduction in biodiversity within the culture reactor. This phenomenon can lead to communities that lack the desired functionality. The objective of this thesis was to study the influence of microbiota propagation, under controlled conditions, on their structure and function. During this work, a process of microbial culture excluding microbial competition for the propagation of bacterial communities was developed. The chosen strategy is based on the micro-confinement and spatial segregation of bacteria within a broth structured as an invert emulsion. The effect of the invert emulsion culture on the growth of individual bacteria was studied, then the effect of this system on the dynamics of communities propagated according to a sequential regime, or backslopping, as well as that exerted by a conventional non-emulsified system was investigated. The results showed that the use of an inverse emulsion leads to the generation of new community structures during propagation, and that the use of the classical culture leads to their stabilization. The different behaviors of these two culture systems make them complementary tools for the modeling and the propagation of microbial communities. Finally, the effect of propagation on the functional variability of communities was studied in a biopreservation context. The screening of propagated raw milk microbiota showed that they differed in terms of robustness and reproducibility of anti-Listeria activity, emphasizing the need to take into account the functional variability of communities when selecting communities of interest for microbiota engineering.Les découvertes récentes sur les communautés microbiennes, ou microbiotes, ont révélé un potentiel biotechnologique considérable dans divers domaines. Ils sont considérés comme essentiels pour accélérer l'innovation dans les systèmes de production alimentaire. Toutefois, les procédés existants ne sont pas adaptés à la culture des microbiotes. La difficulté que représente la culture de microbiotes a notamment pour origine la capacité des microorganismes à interagir par compétition, qui peut conduire à la réduction indésirable de la biodiversité au sein du réacteur de culture. Ce phénomène peut aboutir à l'obtention de communautés qui ne présentent pas les fonctionnalités souhaitées. L'objectif de cette thèse est d'étudier l'influence de la propagation de microbiotes en condition contrôlée sur leur structure et leur fonction. Les travaux de cette thèse ont permis de développer et de déterminer la performance d'un procédé excluant la compétition microbienne pour la culture de communautés bactériennes. La stratégie choisie repose sur le micro-confinement et la ségrégation spatiale des bactéries au sein d'un bouillon de culture structuré en émulsion inverse. Après avoir étudié l'effet de la culture en émulsion inverse sur la croissance de bactéries individuelles, les travaux ont comparé son effet sur la dynamique de communautés propagées selon un régime séquentiel, ou backslopping, avec celui exercé par un système classique non-émulsionné. Les résultats ont montré que l'utilisation d'une émulsion inverse conduit à la génération de nouvelles structures de communautés au cours de la propagation, et que l'utilisation de la culture classique conduit à leur stabilisation. Les comportements différents issus de ces deux systèmes de culture en font des outils complémentaires pour le modelage et la propagation de communautés microbiennes. Enfin, l'effet de la propagation sur la variabilité fonctionnelle de communautés a été étudiée dans un contexte de biopréservation. Le criblage de microbiotes de laits crus propagés a montré qu'ils se différenciaient en termes de robustesse et de reproductibilité de leur activité anti-Listeria, justifiant de tenir compte de la variabilité fonctionnelle des communautés pour leur sélection dans un contexte d'ingénierie de microbiotes
Propagation of bacterial communities : shaping, stabilization and selection for biopreservation
No full textLes découvertes récentes sur les communautés microbiennes, ou microbiotes, ont révélé un potentiel biotechnologique considérable dans divers domaines. Ils sont considérés comme essentiels pour accélérer l'innovation dans les systèmes de production alimentaire. Toutefois, les procédés existants ne sont pas adaptés à la culture des microbiotes. La difficulté que représente la culture de microbiotes a notamment pour origine la capacité des microorganismes à interagir par compétition, qui peut conduire à la réduction indésirable de la biodiversité au sein du réacteur de culture. Ce phénomène peut aboutir à l'obtention de communautés qui ne présentent pas les fonctionnalités souhaitées. L'objectif de cette thèse est d'étudier l'influence de la propagation de microbiotes en condition contrôlée sur leur structure et leur fonction. Les travaux de cette thèse ont permis de développer et de déterminer la performance d'un procédé excluant la compétition microbienne pour la culture de communautés bactériennes. La stratégie choisie repose sur le micro-confinement et la ségrégation spatiale des bactéries au sein d'un bouillon de culture structuré en émulsion inverse. Après avoir étudié l'effet de la culture en émulsion inverse sur la croissance de bactéries individuelles, les travaux ont comparé son effet sur la dynamique de communautés propagées selon un régime séquentiel, ou backslopping, avec celui exercé par un système classique non-émulsionné. Les résultats ont montré que l'utilisation d'une émulsion inverse conduit à la génération de nouvelles structures de communautés au cours de la propagation, et que l'utilisation de la culture classique conduit à leur stabilisation. Les comportements différents issus de ces deux systèmes de culture en font des outils complémentaires pour le modelage et la propagation de communautés microbiennes. Enfin, l'effet de la propagation sur la variabilité fonctionnelle de communautés a été étudiée dans un contexte de biopréservation. Le criblage de microbiotes de laits crus propagés a montré qu'ils se différenciaient en termes de robustesse et de reproductibilité de leur activité anti-Listeria, justifiant de tenir compte de la variabilité fonctionnelle des communautés pour leur sélection dans un contexte d'ingénierie de microbiotes.Recent discoveries about microbial communities, or microbiota, have revealed considerable biotechnological potential in a variety of fields. They are considered essential to accelerate innovation in food production systems. However, existing processes are not adapted to the cultivation of microbiota. One major barrier to community propagation is competition between microorganisms, which can lead to an undesirable reduction in biodiversity within the culture reactor. This phenomenon can lead to communities that lack the desired functionality. The objective of this thesis was to study the influence of microbiota propagation, under controlled conditions, on their structure and function. During this work, a process of microbial culture excluding microbial competition for the propagation of bacterial communities was developed. The chosen strategy is based on the micro-confinement and spatial segregation of bacteria within a broth structured as an invert emulsion. The effect of the invert emulsion culture on the growth of individual bacteria was studied, then the effect of this system on the dynamics of communities propagated according to a sequential regime, or backslopping, as well as that exerted by a conventional non-emulsified system was investigated. The results showed that the use of an inverse emulsion leads to the generation of new community structures during propagation, and that the use of the classical culture leads to their stabilization. The different behaviors of these two culture systems make them complementary tools for the modeling and the propagation of microbial communities. Finally, the effect of propagation on the functional variability of communities was studied in a biopreservation context. The screening of propagated raw milk microbiota showed that they differed in terms of robustness and reproducibility of anti-Listeria activity, emphasizing the need to take into account the functional variability of communities when selecting communities of interest for microbiota engineering
Propagation de communautés bactériennes : modelage, stabilisation et sélection pour la biopréservation
No full textRecent discoveries about microbial communities, or microbiota, have revealed considerable biotechnological potential in a variety of fields. They are considered essential to accelerate innovation in food production systems. However, existing processes are not adapted to the cultivation of microbiota. One major barrier to community propagation is competition between microorganisms, which can lead to an undesirable reduction in biodiversity within the culture reactor. This phenomenon can lead to communities that lack the desired functionality. The objective of this thesis was to study the influence of microbiota propagation, under controlled conditions, on their structure and function. During this work, a process of microbial culture excluding microbial competition for the propagation of bacterial communities was developed. The chosen strategy is based on the micro-confinement and spatial segregation of bacteria within a broth structured as an invert emulsion. The effect of the invert emulsion culture on the growth of individual bacteria was studied, then the effect of this system on the dynamics of communities propagated according to a sequential regime, or backslopping, as well as that exerted by a conventional non-emulsified system was investigated. The results showed that the use of an inverse emulsion leads to the generation of new community structures during propagation, and that the use of the classical culture leads to their stabilization. The different behaviors of these two culture systems make them complementary tools for the modeling and the propagation of microbial communities. Finally, the effect of propagation on the functional variability of communities was studied in a biopreservation context. The screening of propagated raw milk microbiota showed that they differed in terms of robustness and reproducibility of anti-Listeria activity, emphasizing the need to take into account the functional variability of communities when selecting communities of interest for microbiota engineering.Les découvertes récentes sur les communautés microbiennes, ou microbiotes, ont révélé un potentiel biotechnologique considérable dans divers domaines. Ils sont considérés comme essentiels pour accélérer l'innovation dans les systèmes de production alimentaire. Toutefois, les procédés existants ne sont pas adaptés à la culture des microbiotes. La difficulté que représente la culture de microbiotes a notamment pour origine la capacité des microorganismes à interagir par compétition, qui peut conduire à la réduction indésirable de la biodiversité au sein du réacteur de culture. Ce phénomène peut aboutir à l'obtention de communautés qui ne présentent pas les fonctionnalités souhaitées. L'objectif de cette thèse est d'étudier l'influence de la propagation de microbiotes en condition contrôlée sur leur structure et leur fonction. Les travaux de cette thèse ont permis de développer et de déterminer la performance d'un procédé excluant la compétition microbienne pour la culture de communautés bactériennes. La stratégie choisie repose sur le micro-confinement et la ségrégation spatiale des bactéries au sein d'un bouillon de culture structuré en émulsion inverse. Après avoir étudié l'effet de la culture en émulsion inverse sur la croissance de bactéries individuelles, les travaux ont comparé son effet sur la dynamique de communautés propagées selon un régime séquentiel, ou backslopping, avec celui exercé par un système classique non-émulsionné. Les résultats ont montré que l'utilisation d'une émulsion inverse conduit à la génération de nouvelles structures de communautés au cours de la propagation, et que l'utilisation de la culture classique conduit à leur stabilisation. Les comportements différents issus de ces deux systèmes de culture en font des outils complémentaires pour le modelage et la propagation de communautés microbiennes. Enfin, l'effet de la propagation sur la variabilité fonctionnelle de communautés a été étudiée dans un contexte de biopréservation. Le criblage de microbiotes de laits crus propagés a montré qu'ils se différenciaient en termes de robustesse et de reproductibilité de leur activité anti-Listeria, justifiant de tenir compte de la variabilité fonctionnelle des communautés pour leur sélection dans un contexte d'ingénierie de microbiotes
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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