Le cancer figure parmi les principales causes de décès dans le monde. Afin de traiter le cancer, les chimiothérapies en combinaison avec la chirurgie sont les plus utilisées. Des composés organométalliques tel que les sels de platine représentent une référence en clinique. Malgré leur succès, ils comportent des limites qui sont des toxicités sur les tissus sains et le développement de résistances. Notre équipe collabore depuis plusieurs années avec divers chimistes afin de développer de nouvelles molécules organométalliques anticancéreuses à base de Ruthénium (ROC) et à base d'Osmium (ODC). Au cours de ma thèse, j'ai réalisé des études de type structure/fonction de nouvelles molécules afin de trouver les paramètres physicochimiques importants pour leur activité biologique et afin d'identifier leur mode d'action. Mes travaux ont démontré que le potentiel d'oxydoréduction des composés serait un facteur important pour leur cytotoxicité. De plus, j'ai identifié de nouvelles voies de signalisation régulées par ces composés, tels que les voies de signalisation d'Hif-1 et Nrf2, et les HDAC. L'ensemble de ces résultats nous permet de mieux comprendre les propriétés biologiques des composés organométalliques ce qui à terme devrait permettre une optimisation de leur structure pour améliorer leur activité anticancéreuse. / Cancer is one of the leading causes of death in the world. To treat cancer, several therapeutic approaches exist. Chemotherapy in combination with surgery is one of the most used. Organometallic compounds such as platinum salts represent a reference in clinic. Despite their success, they have limitations that are toxicity to healthy tissue and the development of resistance. Our team has been working for several years with chemists to develop new organometallic Ruthenium (ROC) and Osmium compounds (ODC). During my Ph.D. I performed structure/function studies on novel molecules in order to find the important physico chemical parameters for their biological activity. My work demonstrated that the redox potential is a crucial factor for the cytotoxicity of the compounds. ln addition, I identified novel regulatory pathways that are targeted by these compounds, such as the Hif1 and Nrf2 pathways, and the HDACs. All together these results allow us to have a better understanding of the biological properties of the organometallic compounds, which will in time allow a optimization of their structure to favor their anticancer activity.

Made available in DSpace on 2016-06-02T19:30:12Z (GMT). No. of bitstreams: 1 6741.pdf: 15167648 bytes, checksum: a9c6d1fafc3e61950d1dbffe3c66e1bf (MD5) Previous issue date: 2015-02-25 / Universidade Federal de Sao Carlos / The estuarine regions are distributed along the coasts worldwide and show gradients of environmental conditions. Flooding and salinity are often considered the most important factors to influence plant species distribution in estuarine communities. Nevertheless, other factors such as geographic localization, geomorphological formation and variations of the flooding cycles may influence plant community s organization. Some studies also indicate expressive differences in species distribution patterns between temperate and tropical estuaries. Functional diversity may support the understanding of diversity patterns through the distribution and composition of functional traits in plant communities and help us understand the differences among distinct estuaries. Functional traits may be directly measured from plant individuals or determined as categories for each species (or group of species) and must be related to relevant processes in the community. Using the information of functional traits and species composition (or abundance) in each community, we may calculate functional diversity indices and then evaluate its variation patterns along the estuarine gradients. In chapter 1 of this thesis, we investigated the variations of plant functional diversity in three salt marshes of the west coast of England. In salt marshes, soil redox potential water content and the relative tide height are important factors to determine the colonization and species diversity of plant communities. Our results showed that plant functional diversity increased along the flooding gradient and that soil redox potential and relative tide height were the main factors to influence the variation of functional diversity. In chapter 2, we investigated plant functional diversity of two estuaries with distinct flooding cycles (open and closed) in the coast of São Paulo State. We observed that functional diversity varied mainly along the flooding gradient, increasing at higher elevations at both estuaries. Salinity was also important to functional diversity in the open estuary. We also observed functional diversity indices showed higher values at closed estuary. This result might be related to the longer and less predictable flooding cycle in the closed estuary, which generates a less sharp pattern of species distribution, so traits combination and functional diversity are higher. The factor considered important filters for species distribution are also major determinants of plant functional diversity in estuarine communities. Nevertheless, the investigation of functional diversity patterns helps us identify and discuss how the effect of different flooding cycles on estuarine communities. / As regiões estuarinas estão distribuídas ao longo da costa de todo o mundo e apresentam condições ambientais distribuídas em gradientes. O alagamento e a salinidade são considerados os mais importantes fatores a influenciar a distribuição de espécies das comunidades vegetais estuarinas. No entanto, outros fatores como a localização geográfica, a formação geomorfológica e variações nos ciclos de alagamento influenciam a organização das formações vegetais. Alguns estudos apontam também para diferenças expressivas nos padrões de distribuição entre estuários de áreas temperadas e tropicais. A diversidade funcional pode contribuir na compreensão dos padrões de diversidade através da distribuição e composição de traços funcionais das plantas da comunidade e nos ajudar a entender as diferenças existentes entre estuários distintos. Os traços funcionais podem ser medidos diretamente nos indivíduos ou determinados categoricamente para cada espécie (ou grupo de espécies) e devem ser relacionados a processos relevantes na comunidade e às questões de estudo. A partir das informações sobre os traços funcionais e a composição (ou abundância) de suas espécies, podemos calcular os índices de diversidade funcional e, então, avaliar seus padrões de variação ao longo dos gradientes ambientais estuarinos. No capítulo 1, investigamos a diversidade funcional em três marismas da costa leste da Inglaterra. Nos marismas, o potencial redox, a quantidade de água e a altura relativa da maré são fatores importantes para determinar a colonização e a diversidade de espécies da comunidade vegetal. Nossos resultados indicaram que a diversidade funcional da comunidade aumentou em relação ao gradiente de alagamento e que o potencial redox e a altra relativa da maré foram os principais fatores medidos a influenciar a variação da diversidade funcional. No capítulo 2, investigamos a diversidade funcional de dois estuários com ciclos de alagamento distintos (aberto e fechado) no litoral do estado de São Paulo. Observamos que a diversidade funcional variou principalmente em relação ao gradiente de alagamento, aumentando em elevações mais altas nos dois estuários. A salinidade foi também importante 27! para a diversidade funcional no estuário aberto. Observamos também os índices de diversidade funcional atingem valores maiores no estuário fechado. Este resultado deve ser devido ao ciclo de alagamento mais longo e menos previsível do estuário fechado, que gera um padrão de distribuição de espécies menos claro, de forma que a combinação de traços e, consequentemente, a diversidade funcional sejam maiores. Os fatores considerados importantes filtros da distribuição de espécies também são significativamente determinantes da diversidade funcional de comunidade vegetais estuarinas. No entanto, a investigação da diversidade funcional permite identificar e discutir como as variáveis afetam as comunidades estuarinas de forma mais detalhada, permitindo entender a influência dos diferentes ciclos de alagamento sobre estas comunidades.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2017-02-08T10:12:21Z No. of bitstreams: 2 Dissertação - Gustavo de Melo Oliveira Gonçalves - 2016.pdf: 1630959 bytes, checksum: 90d5f7c22407381803a1e520c265c080 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-02-08T10:12:49Z (GMT) No. of bitstreams: 2 Dissertação - Gustavo de Melo Oliveira Gonçalves - 2016.pdf: 1630959 bytes, checksum: 90d5f7c22407381803a1e520c265c080 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-02-08T10:12:49Z (GMT). No. of bitstreams: 2 Dissertação - Gustavo de Melo Oliveira Gonçalves - 2016.pdf: 1630959 bytes, checksum: 90d5f7c22407381803a1e520c265c080 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-07-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In the last years, due to the government effort, especially in the Tocantins State, there have been significante increase on flooded rice production areas. However, there are few studies about nitrogen sources and doses in that region, which could improve the nitrogen efficiency use and provide higher incomes for farmers. This study aimed to determine the effects of different sources and doses of nitrogen in flooded lowland soils in the pH, redox potential and the concentration of ions in the soil solution in order to obtain the economicallyand environmentally best mineral nitrogen source and dose. The samples were collected in the 2014/2015 season at the Embrapa Rice and Beans Experimental Field - Palmital Farm-, in a Dystric Gleysol. The design was a complete randomized blocks, with four replications, two sources of nitrogen (common urea and slow release urea), three nitrogen rates (30, 70, 150 kg ha-1), and a control, without any N application.Soil solution samples were collected weekly, during the flooded period in rice cultivation, BRS Catiana genotype. The pH analysis and Eh (redoxpotential) were immediately read, just after the soil solution sampling, in the field, and thenHCl (2M) acidified,, and immediately frozen for later analysis of the following ions: Ca, Mg, K, Fe, Zn, Mn, MOS, NO3- and NH4+. The sources used did not affect the release of nutrients dynamics to the soil solution. The anaerobic condition caused changes in the Eh and ions solubility in the soil solution. The doses applied changed Ca and MOS concentrations in solution, and the dose of 150 kg ha-1 N showed the highest values for both. / Nos últimos anos, devido incentivos do governo, especialmente no Estado do Tocantins, houve significante aumento em áreas de produção de arroz irrigado. No entanto, existem poucos estudos sobre fontes de nitrogênio e doses naquela região, o que poderia melhorar a eficiência de uso de nitrogênio e proporcionar maiores rendimentos para os produtores rurais. O presente trabalho teve como objetivo determinar os efeitos de diferentes fontes e doses de nitrogênio em solos de várzea inundados no pH, potencial redox e na concentração de íons da solução do solo, visando a obtenção da fonte e dose de fertilizante economicamente viável e ambientalmente sustentável. As amostras foram coletadas na safra 2014/2015 no Campo Experimental da Fazenda Palmital, da Embrapa Arroz e Feijão, em Gleissolo Háplico. O delineamento utilizado foi o de blocos casualizados com quatro repetições, sendo duas fontes de nitrogênio (ureia comum e ureia de liberação lenta), três doses de N aplicadas em cobertura (30, 70, 150 kg ha-1), e a testemunha absoluta, sem aplicação alguma de N. Foram coletadas amostras de solução do solo, semanalmente, durante o período de inundação no cultivo do arroz, cultivar BRS Catiana. As análises de pH e Eh (potencial de oxirredução) foram feitas logo após a coleta da solução do solo no campo, e então, acidificadas com HCl (2M), e imediatamente congeladas para posterior análise dos seguintes elementos: Ca, Mg, K, Fe, Zn, Mn, MOS, NO3- e NH4+. As fontes utilizadas não interferiram na dinâmica de liberação dos nutrientes para solução do solo. A condição de anaerobiose causou modificações no estado de oxirredução e alterou a solubilidade dos nutrientes na solução do solo. As doses aplicadas alteraram as concentrações de Ca e MOS na solução, sendo a dose de 150 kg ha-1 de N a dose que apresentou os maiores valores para ambos.

Abstract There are many methods for the restorating a eutrophicated lake. This study has concentrated on chemical treatment of the sediment and the restoration measurements. This study is divided into three parts: studies of the chemical restoration of study lakes, the optimization of the sediment chemical restoration method, and the evaluation of the method effectiveness of the lake restoration. According to the results, it is possible to adsorb phosphorus to the sediment and keep it adsorbed, but chemical treatment will not improve the long term phosphorus adsorption capacity of the sediments. Therefore, the internal phosphorus load from sediments is only temporarily decreased. Contrary to the claims of earlier studies, the chemical treatment should be executed with small doses successively over many years. In this case, the phosphorus from the hypolimnion and the interstitial water is engaged and stored in the sediment. The phosphorus will remain stored unless the acidity of the sediment changes so that the phosphorus-aluminum bond is broke. The most important factors in the sediment chemical restoration are the pH-reaction of the chemical and sediment-water mixture. Also, available phosphorus that can be engaged is important. In addition, the natural variety of the pH-value of the lake must be considered. A laboratory test was made that compared the suitability of five different chemicals for the restoration of lakes. The tested chemicals were chemicals that are commonly used in the production of drinking water and in waste water treatment. The most suitable chemical for lake restoration was Kemira’s CFH0818 which had the best ability to engage phosphorus and the best pH-reaction. The successfulness of the lake restoration can be determined from the phosphate in the interstitial water of the sediment as a primary source of internal phosphorus load. This diffusion calculation can be made in every restoration object before and after the restoration measures. Also, oxygen conditions, pH-value and the process environment of the breakdown of the organic material are determined as tools for the restoration measures. The use of the evaluation methods is mostly limited by the dynamic nature of the process environment over different seasons of the year. So for reliable restoration measurement one must know why, when and where the measurements are made. / Tiivistelmä Rehevän järven kunnostamiseksi on useita menetelmiä: joista tässä tutkimuksessa on keskitytty sedimentin kemikaalikäsittelyyn sekä sen tuloksellisuuden mittaamiseen. Tutkimus jakautuu kolmeen osaan: kemikaalikunnostusten järvikohtaiseen tarkasteluun, sedimentin kemikaalikunnostuksen mitoituksen optimointiin sekä järvikunnostuksen tuloksellisuuden arvioimiseen. Tutkimustulosten mukaan sedimentin kemikaloinnilla voidaan sitoa järvessä kiertävää fosforia sedimenttiin, mutta pysyvää sedimentin fosforinsidontakykyä kertaluontoisella kemikaloinnilla ei saavuteta. Järven sisäinen kuormitus siis hetkellisesti hidastuu, mutta ei lopu sedimentin kemikalointiin. Kemikalointi tulee tehdä pienin kerta-annoksin useana vuonna peräkkäin ja sedimentin pH:n tulisi säilyä välillä 6–8 läpi vuoden. Tällöin kemikaali varastoi sitomansa fosforin sedimenttiin. Kemikaalikunnostuksen tärkeimmät mitoitustekijät ovat kemikaalin pH-vaste vesimassaan ja sedimenttiin sekä sidottavissa oleva fosforimäärä kunnostettavassa järvessä. Tutkimuksen mukaan PAX-18-kemikaali ja vastaavat liuosmaiset alumiini- ja rautakemikaalit eivät ole ensisijaisia järvikunnostuskemikaaleja. Ne on kehitetty juoma- ja jäteveden puhdistamiseen, eli sitomaan nopeasti fosforia ja orgaanista ainetta. Sitä vastoin laboratoriokokeen tulosten perusteella rakeiset adsorptio-kemikaalit, kuten Kemiran CFH0818 sitovat sedimentin fosforia itseensä ilman merkittäviä happamoitumisvaikutuksia. Järvikunnostuksen tuloksellisuutta voidaan arvioida mittaamalla sedimentissä vapaana oleva fosfaattimäärä ja sedimentin hapetustila, happamuus sekä määrittämällä sedimentin fosforinsidontakyky. Mittaukset on tehtävä ennen ja jälkeen kunnostustoimia. Näiden mittausten perusteella voidaan kunnostustoimien tuloksellisuutta arvioida varsin luotettavasti. Tulosten käyttöä rajoittavat lähinnä muuttuvat prosessiolosuhteet eri vuodenaikoina ja toistaiseksi riittävän vertailuaineiston puute. Järvikunnostuksen tuloksellisuuden arvioimiseksi on tiedettävä kohdekohtaisesti miksi, milloin ja mistä mitataan, jotta arvio on luotettava.

Cette thèse porte sur deux projets visant au développement de nouvelles approches pour simuler les dynamiques moléculaire et électronique avec application à des biomolécules étendues. Dans la première partie nous cherchons à améliorer significativement la précision des simulations des propriétés rédox des protéines. Dans ce contexte, l'objectif est de recourir à de champ de force reposant sur une description multipolaire des interactions électrostatiques (AMOEBA) pour estimer les potentiels redox d'hémoprotéines. Nous avons dérivé des paramètres pour AMOEBA afin de décrire précisément les interactions électrostatiques avec l'hème. Une amélioration très encourageante est obtenue par rapport aux champs de forces standard. Le second projet vise à développer de nouvelles méthodes pour étudier la dynamique des électrons dans des biomolécules à l'échelle attoseconde en incluant les effets d'environnement. Nous avons conçu un couplage original entre la théorie de la fonctionnelle de la densité dépendant du temps (RT-TDDFT) et un modèle de mécanique moléculaire polarisable (MMpol). Une implémentation efficace et robuste de cette méthode a été réalisée dans le logiciel deMon2k. L'utilisation de techniques d'ajustements de densités électroniques auxiliaires permet de réduire drastiquement le coût de calcul des propagations RT-TDDFT/MMpol. La méthode est appliquée à l'analyse de la dissipation d'énergie dans l'environnement d'un peptide excité par un impulsion laser. / This thesis involves two projects devoted to the development of advanced approaches for simulating molecular and electron dynamics in extended biomolecules. The first project aims at significantly improving the accuracy of redox potentials of proteins by numerical simulations. A sophisticated force field relying on a multipolar description of electrostartic interactions (AMOEBA) is used to perform molecular dynamics simulations onheme proteins. We derived parameters for AMOEBA to accurately describe electrostatic interactions with hemein both ferrous and ferric states. Very encouraging improvements are obtained compared to the standard force fields. The second project aims at developing original approaches for simulating ultrafast electron dynamics in biomolecules in contact to polarizable environments. We devised acombination of Real-time Time-Dependent Density Functional Theory (RT-TDDFT) and polarizable Molecular Mechanics (MMpol). An efficient and robust implementation of this method has been realized in deMon2k software. Density fitting techniques allow to reduce the computational cost of RT-TDDFT/MMpol propagations. The methodology is applied to understand the mechanisms of energy dissipation of a peptide excited by a laser pulse.

Biofuel production via fermentation is produced primarily by fermentation of simple sugars. Besides the sugar fermentation route, there exists a promising alternative process that uses syngas (CO, H2, CO2) produced from biomass as building blocks for biofuels. Although syngas fermentation has many benefits, there are several challenges that still need to be addressed in order for syngas fermentation to become a viable process for producing biofuels on a large scale. One challenge is mass transfer limitations due to low solubilities of syngas species. The hollow fiber reactor (HFR) is one type of reactor that has the potential for achieving high mass transfer rates for biofuels production. However, a better understanding of mass transfer limitations in HFRs is still needed. In addition there have been relatively few studies performing actual fermentations in an HFR to assess whether high mass transfer rates equate to better fermentation results. Besides mass transfer, one other difficulty with syngas fermentation is understanding the role that CO and H2 play as electron donors and how different CO and H2 ratios effect syngas fermentation. In addition to electrons from CO and H2, electrodes can also be used to augment the supply of electrons or provide the only source of electrons for syngas fermentation. This work performed an in depth reactor comparison that compared mass transfer rates and fermentation abilities. The HFR achieved the highest oxygen mass transfer coefficient (1062 h-1) compared to other reactors. In fermentations, the HFR showed very high production rates (5.3 mMc/hr) and ethanol to acetic acid ratios (13) compared to other common reactors. This work also analyzed the use of electrons from H2 and CO by C. ragsdalei and to study the effects of these two different electron sources on product formation and cell growth. This study showed that cell growth is not largely effected by CO composition although there must be at least some minimum amount of CO present (between 5-20%). Interestingly, H2 composition has no effect on cell growth. Also, more electron equivalents will lead to higher product formation rates. Following Acetyl-CoA formation, H2 is only used for product formation but not cell growth. In addition to these studies on electrons from H2 and CO, this work also assessed the redox states of methyl viologen (MV) for use as an artificial electron carrier in applications such as syngas fermentation. A validated thermodynamic model was presented in order to illustrate the most likely redox state of MV depending on the system setup. Variable MV extinction coefficients and standard redox potentials reported in literature were assessed to provide recommended values for modeling and analysis. Model results showed that there are narrow potential ranges in which MV can change from one redox state to another, thus affecting the potential use as an artificial electron carrier.

Les oxydants infusés avec la nutrition parentéral (NP) néonatale induisent une modification du métabolisme des lipides et du glucose, donnant lieu à l’âge adulte à un phénotype de carence énergétique (faible poids, baisse de l’activité physique). L’hypothèse qu’une diète précoce riche en glucose prévient ces symptômes plus tard dans la vie, fut évalué chez le cobaye par un ANOVA en plan factoriel complet à deux facteurs (p < 0:05) : NP du jour 3 à 7, suivit d’une nourriture régulière (chow) (NP+) vs. chow à partir du 3ième jour (NP-), combiné avec une eau de consommation enrichie en glucose (G+) ou non (G-) à partir de la 3ième semaine. Les paramètres suivant ont été mesurés à l’âge de 9 semaine: taux de croissance, activité physique, activité de phosphofructokinase-1 et glucokinase (GK), niveau hépatique de glucose-6-phosphate (G6P), glycogène, pyruvate et potentiel redox du glutathion, poids du foie, glycémie, tolérance au glucose, concentrations hépatiques et plasmatiques en triacylglycérides (TG) et cholestérol. Le groupe G+ (vs. G-) avait un taux de croissance plus bas, une activité de GK et une concentration en G6P plus élevée, et un potentiel redox plus bas (moins oxydé). Le niveau plasmatique de TG était moins élevé dans le groupe NP+ (vs. NP-). Les traitements n’eurent aucun effet sur les autres paramètres. Ces résultats suggèrent qu’indépendamment de la NP, une alimentation riche en glucose stimule la glycolyse et déplace l’état redox vers un statut plus réduit, mais ne surmonte pas les effets de la NP sur le phénotype physique de carence énergétique. / Neonatal exposure to oxidant molecules from total parenteral nutrition (TPN) alters future lipid and glucose metabolism, resulting in an energy deficient phenotype characterized by lower body weight and physical activity. Using a guinea-pig model, the hypothesis that early diet supplementation with glucose could overcome such symptoms at week 9 of age was tested in a two-factor full-factorial ANOVA design (p<0:05): TPN day 3-7, chow thereafter (TPN+) vs: chow from day 3 (TPN-), combined with glucose-enriched diet from week 3 (G+) vs: plain chow throughout (G-). The growth rate, physical activity, phosphofructose kinase-1 and glucose kinase (GK) activities, glucose-6-phosphate (G6P), glycogen and pyruvate concentrations, relative liver weight, fasting blood glucose, glucose tolerance, hepatic and plasma triacylglyceride and cholesterol levels, individual glutathione levels and GSH/GSSG-based redox potential were determined at 9 weeks. Glucose supplementation (vs: the lack thereof) resulted in a lower growth rate, higher GK activity, and higher G6P concentration at week 9. Plasma triacylglycerides at week 9 were lower in TPN+ (vs: TPN-) subjects. Hepatic GSH=GSSG-derived redox potential shifted to a more reduced state in G+ (vs: G-) subjects. No other parameters showed significant differences. Independently of TPN, an early glucose-rich diet stimulated the glycolysis pathway, shifted the redox potential towards a more reduced status ; however, it did not overcome the effects of TPN on future physical and metabolic phenotype.

Les oxydants infusés avec la nutrition parentéral (NP) néonatale induisent une modification du métabolisme des lipides et du glucose, donnant lieu à l’âge adulte à un phénotype de carence énergétique (faible poids, baisse de l’activité physique). L’hypothèse qu’une diète précoce riche en glucose prévient ces symptômes plus tard dans la vie, fut évalué chez le cobaye par un ANOVA en plan factoriel complet à deux facteurs (p < 0:05) : NP du jour 3 à 7, suivit d’une nourriture régulière (chow) (NP+) vs. chow à partir du 3ième jour (NP-), combiné avec une eau de consommation enrichie en glucose (G+) ou non (G-) à partir de la 3ième semaine. Les paramètres suivant ont été mesurés à l’âge de 9 semaine: taux de croissance, activité physique, activité de phosphofructokinase-1 et glucokinase (GK), niveau hépatique de glucose-6-phosphate (G6P), glycogène, pyruvate et potentiel redox du glutathion, poids du foie, glycémie, tolérance au glucose, concentrations hépatiques et plasmatiques en triacylglycérides (TG) et cholestérol. Le groupe G+ (vs. G-) avait un taux de croissance plus bas, une activité de GK et une concentration en G6P plus élevée, et un potentiel redox plus bas (moins oxydé). Le niveau plasmatique de TG était moins élevé dans le groupe NP+ (vs. NP-). Les traitements n’eurent aucun effet sur les autres paramètres. Ces résultats suggèrent qu’indépendamment de la NP, une alimentation riche en glucose stimule la glycolyse et déplace l’état redox vers un statut plus réduit, mais ne surmonte pas les effets de la NP sur le phénotype physique de carence énergétique. / Neonatal exposure to oxidant molecules from total parenteral nutrition (TPN) alters future lipid and glucose metabolism, resulting in an energy deficient phenotype characterized by lower body weight and physical activity. Using a guinea-pig model, the hypothesis that early diet supplementation with glucose could overcome such symptoms at week 9 of age was tested in a two-factor full-factorial ANOVA design (p<0:05): TPN day 3-7, chow thereafter (TPN+) vs: chow from day 3 (TPN-), combined with glucose-enriched diet from week 3 (G+) vs: plain chow throughout (G-). The growth rate, physical activity, phosphofructose kinase-1 and glucose kinase (GK) activities, glucose-6-phosphate (G6P), glycogen and pyruvate concentrations, relative liver weight, fasting blood glucose, glucose tolerance, hepatic and plasma triacylglyceride and cholesterol levels, individual glutathione levels and GSH/GSSG-based redox potential were determined at 9 weeks. Glucose supplementation (vs: the lack thereof) resulted in a lower growth rate, higher GK activity, and higher G6P concentration at week 9. Plasma triacylglycerides at week 9 were lower in TPN+ (vs: TPN-) subjects. Hepatic GSH=GSSG-derived redox potential shifted to a more reduced state in G+ (vs: G-) subjects. No other parameters showed significant differences. Independently of TPN, an early glucose-rich diet stimulated the glycolysis pathway, shifted the redox potential towards a more reduced status ; however, it did not overcome the effects of TPN on future physical and metabolic phenotype.

L'objectif de ce travail était de sélectionner de manière rationnelle une bactérie probiotique par la mise en place d'un crible ainsi que d'étudier et de comprendre l'impact du potentiel d'oxydoréduction (Eh) et du bullage de gaz sur la survie de Bifidobacterium bifidum dans un produit laitier fermenté. Nous avons tout d’abord développé des techniques de sélection des bactéries sur des critères de viabilité / vitalité (analyse par cytométrie en flux) ainsi que sur des critères de fonctionnalité (pouvoir antioxydant). Nous avons pu sélectionner des souches d'intérêt industriel ainsi qu'une souche d'étude académique, Bifidobacterium bifidum.Nous avons ensuite étudié l'effet de la modification du Eh par bullage de gaz sur la survie de B. bifidum dans un produit laitier fermenté. Les laits fermentés conditionnés sous atmosphère anaérobie (Azote) et/ou réductrice (Azote-Hydrogène) permettent une meilleure survie de la souche au cours du stockage (28 jours – 4 °C) par rapport au Contrôle. Puis, nous avons analysé l'effet d'une croissance sous différents Eh sur la viabilité en milieu modèle et la fonctionnalité de B. bifidum. Une croissance en condition anaérobie et/ou réductrice permet d’améliorer à la fois la résistance aux stress (stress oxydant d’ordre physiologique, stress aux sels biliaires et stress côlon), le pouvoir réducteur (sels de tétrazolium), le pouvoir antioxydant (test KRL et test des comètes) et l’adhérence par rapport au Contrôle. Une modulation des propriétés biochimiques membranaires sous Azote et sous Azote-Hydrogène pourraient expliquer ces phénomènes. L’augmentation des composés thiols exofaciaux et l’augmentation des acides gras insaturés à longues chaines est observée pour des cellules produites sous conditions Azote et Azote-Hydrogène. Ainsi ces conditions de croissance présentent une amélioration majeure de l’effet probiotique de B. bifidum, à la fois d’un point de vue de sa résistance aux stress que d’un point de vue de sa fonctionnalité / The aim of this work was to select rationally a probiotic strain by setting up a screening method as well as study and understand the impact of the redox potential (Eh) and gas bubbling on the survival of Bifidobacterium bifidum in a fermented dairy product. In a first time, we have developed selection techniques of probiotic bacteria on the criteria of viability / vitality (flow cytometry analysis) and on the criteria of functionality (antioxidant). We were able to select strains of industrial interest as well as an academic strain, Bifidobacterium bifidum.Secondly, we have studied effect of modifying redox potential by gas bubbling on the survival of B. bifidum in a fermented dairy product. Thus, fermented milk manufactured under anaerobic condition (Nitrogen,) and/or under reducing one (Nitrogen-Hydrogen) allow a better survival of the probiotic strain during the storage (28 days) at 4 °C compared with the Control fermented milk. Yogurt starter strains are not impacted. Then, we have analysed the effect of a growth under various Eh on the viability in model medium and the functionality of B. bifidum. A growth under anaerobic and/or reducing condition thus improved resistance to stress (physiological oxidative stress, bile salts and intestinal stress) the reducing power (tetrazolium salts) and the antioxidant power (KRL test and comet assay) compared with the Control. The adhesion to Caco-2 cells under these conditions is also improvedModulation of biochemical membrane properties under Azote and Azote-Hydrogen conditions could explain these phenomena. An increase in the proportion of exofacial thiol groups and in the proportion of unsaturated fatty acids with long chain was observed for cells produced under Nitrogen and Nitrogen-Hydrogen. These growth conditions present a major improvement for the probiotic effect of B. bifidum, regarding its resistance to stress and its functionality

Parmi les bactéries lactiques, Lactococcus lactis est la plus utilisée en fabrication fromagère. Actuellement, les ferments lactiques sont majoritairement choisis pour leurs propriétés acidifiantes, protéolytiques et aromatiques. Un autre paramètre majeur est le potentiel redox (Eh). En effet, un Eh réducteur est souvent associé à une bonne qualité aromatique. L’activité réductrice de L. lactis pourrait donc être un nouveau paramètre à prendre en compte dans la maitrise du Eh dans la fabrication des produits laitiers fermentés. Néanmoins, les mécanismes impliqués dans l’activité réductrice de L. lactis demeurent encore inconnus. L’objectif de ce présent travail de thèse a été de les découvrir. Tout d’abord, nous avons développé des milieux de culture gélosé de discrimination redox utilisant des sels de tétrazolium pour cribler une banque de mutants aléatoires de L. lactis. Ceci a permis de démontrer la participation partielle de la chaine de transport d’électrons (Ménaquinones) dans l’activité réductrice de L. lactis. Ensuite, l’approche biochimique nous a permis de déterminer les composés biochimiques principaux contribuant à la diminution du Eh vers des valeurs très réductrices. La présence de groupements thiols exofaciaux est responsable du Eh réducteur atteint par L. lactis. Enfin, l’analyse protéomique utilisant un marquage spécifique des protéines thiols de surface a mis en évidence la présence d’une dizaine de protéines exposant des groupements thiols exofaciaux potentiellement impliquées dans l’activité réductrice de L. lactis. Les thiols sont connus pour être de très puissants antioxydants ce qui confère à L. lactis un intérêt supplémentaire à prendre en considération dans l’élaboration des produits laitiers fermentés. / Among the Lactic Acid Bacteria, Lactococcus lactis is the most used in cheese making. Nowadays, starters are used mainly for their acidifying, proteolytic and flavor properties. Another important parameter is the redox potential (Eh). Indeed, reducing Eh is often related to good flavor properties. The reducing activity of L.lactis should be therefore a new parameter to take into account in the monitoring of Eh during dairy fermented products making. Nevertheless, the mechanisms involved in the reducing activity of L.lactis are still unknown. The aim of this work was to understand them. First of all, we have developed tetrazolium salts agar plate media in order to screen a random bank of mutants of L. lactis on their redox capacities. These media allowed us to demonstrate the partial implication of the electron transport chain (Menaquinone) in the reducing activities of L. lactis. Secondly, we have determined the biochemical compounds involved in the decrease of Eh to very reducing values thanks to a biochemical approach. Exofacial thiol groups are mainly responsible for the reducing Eh reached by L.lactis. Lastly, a proteomical analysis using a specific staining of thiols surface proteins revealed the presence of about ten proteins displaying thiols exofacials groups. These proteins might be involved in the reducing activity of L.lactis. Thiols are known to be very strong antioxidants which confer to L. lactis an additional interest to consider in dairy products making.