Gene Transcription Patterns of pH- and Salt-Stressed Listeria monocytogenes Cells in Simulated Gastric and Pancreatic Conditions

A Listeria monocytogenes subgenomic array, targeting 54 genes involved in the adhesion, adaptation, intracellular life cycle, invasion, and regulation of the infection cycle was used to investigate the gene expression patterns of acid- and salt-stressed Listeria cells after exposure to conditions similar to those in gastric and pancreatic fluids. Three L. monocytogenes strains, one laboratory reference strain (EGDe) and two food isolates (wild strain 12 isolated from milk and wild strain 3 isolated from fermented sausage), were used during the studies. Differences in the expressed genes were observed between the gastric and pancreatic treatments and also between the serotypes. Increased transcripts were observed of the genes belonging to the adaptation and regulation group for serotype 4b (strain 12) and to the invasion and regulation group for serotype 1/2a (strain EGDe). Interestingly, no significantly differentially expressed genes were found for serotype 3c (strain 3) in most cases. The genes related to adaptation (serotype 1/2a) and to intracellular life cycle and invasion (serotype 4b) were down-regulated in order to cope with the hostile environment of the gastric and pancreatic fluids. These findings may provide experimental evidence for the dominance of serotypes 1/2a and 4b in clinical cases of listeriosis and for the sporadic occurrence of serotype 3c

In vitro Modeling of Chicken Cecal Microbiota Ecology and Metabolism Using the PolyFermS Platform

Continuous in vitro fermentation models provide a useful tool for a fast, reproducible, and direct assessment of treatment-related changes in microbiota metabolism and composition independent of the host. In this study, we used the PolyFermS model to mimic the conditions of the chicken cecum and evaluated three nutritive media for in vitro modeling of the chicken cecal microbiota ecology and metabolism. We observed that our model inoculated with immobilized cecal microbiota and fed with a modified Viande Levure medium (mVL-3) reached a high bacterial cell density of up to approximately 10.5 log cells per mL and stable microbiota composition, akin to the host, during 82 days of continuous operation. Relevant bacterial functional groups containing primary fibrolytic (Bacteroides, Bifidobacteriaceae, Ruminococcaceae), glycolytic (Enterococcus), mucolytic (Bacteroides), proteolytic (Bacteroides), and secondary acetate-utilizing butyrate-producing and propionate-producing (Lachnospiraceae) taxa were preserved in vitro. Besides, conserved metabolic and functional Kyoto Encyclopedia of Genes and Genomes pathways were observed between in vitro microbiota and cecal inoculum microbiota as predicted by functional metagenomics analysis. Furthermore, we demonstrated that the continuous inoculation provided by the inoculum reactor generated reproducible metabolic profiles in second-stage reactors comparable to the chicken cecum, allowing for the simultaneous investigation and direct comparison of different treatments with a control. In conclusion, we showed that PolyFermS is a suitable model for mimicking chicken cecal microbiota fermentation allowing ethical and ex vivo screening of environmental factors, such as dietary additives, on chicken cecal fermentation. We report here for the first time a fermentation medium (mVL-3) that closely mimics the substrate conditions in the chicken cecum and supports the growth and metabolic activity of the cecal bacterial akin to the host. Our PolyFermS chicken cecum model is a useful tool to study microbiota functionality and structure ex vivo

Understanding the prebiotic potential of different dietary fibers using an <em>in vitro</em> continuous adult fermentation model (PolyFermS)

Abstract Consumption of fermentable dietary fibers (DFs), which can induce growth and/or activity of specific beneficial populations, is suggested a promising strategy to modulate the gut microbiota and restore health in microbiota-linked diseases. Until today, inulin and fructo-oligosaccharides (FOS) are the best studied DFs, while little is known about the gut microbiota-modulating effects of β-glucan, α-galactooligosaccharide (α-GOS) and xylo-oligosaccharide (XOS). Here, we used three continuous in vitro fermentation PolyFermS model to study the modulating effect of these DFs on two distinct human adult proximal colon microbiota, independently from the host. Supplementation of DFs, equivalent to a 9 g daily intake, induced a consistent metabolic response depending on the donor microbiota. Irrespective to the DF supplemented, the Bacteroidaceae-Ruminococcaceae dominated microbiota produced more butyrate (up to 96%), while the Prevotellaceae-Ruminococcaceae dominated microbiota produced more propionate (up to 40%). Changes in abundance of specific bacterial taxa upon DF supplementation explained the observed changes in short-chain fatty acid profiles. Our data suggest that the metabolic profile of SCFA profile may be the most suitable and robust read-out to characterize microbiota-modulating effects of a DF and highlights importance to understand the inter-individual response to a prebiotic treatment for mechanistic understanding and human application

Stepwise establishment of functional microbial groups in the infant gut between 6 months and 2 years: A prospective cohort study

The early intestinal colonization of functional microbial groups plays an essential role in infant gut health, with most studies targeting the initial colonization period from birth to 6 months of age. In a previous report, we demonstrated the metabolic cross-feeding of lactate and identified keystone species specified for lactate utilization in fecal samples of 40 healthy infants. We present here the extension of our longitudinal study for the period from 6 months to 2 years, with a focus on the colonization of functional groups involved in lactate metabolism and butyrate production. We captured the dynamic changes of the gut microbiota and reported a switch in the predominant lactate-producing and lactate-utilizing bacteria, from Veillonella producing propionate in the first year to Anaerobutyrycum hallii producing butyrate in the second year of life. The significant increase in butyrate producers and fecal butyrate concentration was also pinpointed to the weaning period between 6 and 10 months. Correlation analyses further suggested, for the first time, the metabolic cross-feeding of hydrogen in infants. In conclusion, our longitudinal study of 40 Swiss infants provides important insights into the colonization of functional groups involved in lactate metabolism and butyrate production in the first 2 years of life

Scuola, diritti umani e cittadinanza europea. Percorsi di formazione e ricerca-azione nelle scuole del Piemonte

Educare nella scuola ai diritti e ai doveri dei futuri cittadini, alla ricerca di un senso civico e della cosa pubblica di cui oggi abbiamo molto bisogno: temi importanti e difficili, che ricadono fra le tante responsabilità della scuola italiana e dei suoi insegnanti e su cui la Fondazione Agnelli ha avviato un percorso di collaborazione con l’Ufficio Scolastico Regionale del Piemonte che il volume documenta.- Indice #5- Prefazione, Anna Maria Dominici #9- Prefazione, Marco Demarie #13- Introduzione al progetto Educazione alla cittadinanza e alla solidarietà: cultura dei diritti umani, Luigi Catalano #15- Il progetto nazionale, Simonetta Fichelli #17- Il progetto regionale, Carla Fiore #23- Guida alla lettura #29- Saggi #31- La protezione internazionale dei diritti umani, Edoardo Greppi #33- La protezione europea dei diritti umani nella Carta di Nizza, Jörg Luther #45- Scuola e società multietnica, Lorenzo Fischer #57- Scuola, islam e il dibattito sui diritti dell’uomo, Andrea Pacini #65- I progetti delle scuole piemontesi #75- Appendici #157- Appendice A Scheda progetto nazionale 2003 Educazione alla cittadinanza e alla solidarietà: cultura dei diritti umani #159- Appendice B Diritti in mostra, Gemma Re #171Appendice C L’Osservatorio sulla Convenzione Europea, Stefano Milia #17