Orientador: Jaime Maia dos Santos / Banca: Marineide Mendonça Aguillera / Banca: Maria Amélia dos Santos / Banca: Arlindo Leal / Banca: Modesto Barreto / Resumo: Os nematóides das lesões radiculares (Pratylenchus spp.) são considerados o segundo grupo de fitonematóides de maior importância econômica em todo o mundo. A morfologia e a morfometria das seis espécies mais comuns desses nematóides, no Brasil, a saber: Pratylenchus brachyurus, P. coffeae, P. jaehni, P. penetrans, P. vulnus e P. zeae, foram estudas aos microscópios óptico composto e eletrônico de varredura. Os dados foram analisados, também, por análise discriminante e análise canônica, tendo sido determinada uma equação da função de classificação para cada uma das espécies. Conquanto cada uma das espécies possa ser identificada por qualquer das ferramentas utilizadas, a análise morfológica, a análise morfométrica, assim como as análises discriminante e canônica devem ser consideradas ferramentas complementares no processo de identificação das espécies, aumentando a confiabilidade da identificação. Uma grade politômica ilustrada para identificação rápida dessas espécies foi elaborada. A técnica de multiplicação in vitro dessas espécies em cilindro de cenoura mostrou-se adequada para produção massiva desses nematóides, sendo que P. penetrans e P. jaehni foram as espécies que produziram, respectivamente, o maior e o menor número de indivíduos e ovos por cilindro de cenoura, aos 120 dias após a inoculação. / Abstract: The lesion nematodes (Pratylenchus spp.) are considered the second largest group of plant parasitic nematodes of economic importance in the world. The morphology and morphometry of the six more common species of these nematodes in Brazil, namely: Pratylenchus brachyurus, P. coffeae, P. jaehni, P. penetrans, P. vulnus and P. zeae, were studied at the light and scanning electron microscopes. The data were also submitted to discriminant and canonical analyses and an equation of the classification function for each one of the species was determinated. Althought each one of the species can be identified by any of the tools used, the morphologic and morphometric analyses, as well as the discriminant and canonical analyses, must be considered complementary tools in the process of species identification, thus increasing the reliability of the identification. An illustrated polytomous key for a fast identification of these species was elaborated. The in vitro multiplication technique of these species in carrot cylinder was suitable for massive production of these nematodes. Pratylenchus penetrans and P. jaehni were the species that produced, respectively, the greatest and the smallest number of individuals and eggs for carrot cylinder, 120 days after the inoculation. / Doutor

Made available in DSpace on 2014-06-11T19:33:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-11-06Bitstream added on 2014-06-13T19:23:57Z : No. of bitstreams: 1 gonzaga_v_dr_jabo.pdf: 2262058 bytes, checksum: 9f1c54256f73cca2fe58faf334cc3382 (MD5) / Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) / Os nematóides das lesões radiculares (Pratylenchus spp.) são considerados o segundo grupo de fitonematóides de maior importância econômica em todo o mundo. A morfologia e a morfometria das seis espécies mais comuns desses nematóides, no Brasil, a saber: Pratylenchus brachyurus, P. coffeae, P. jaehni, P. penetrans, P. vulnus e P. zeae, foram estudas aos microscópios óptico composto e eletrônico de varredura. Os dados foram analisados, também, por análise discriminante e análise canônica, tendo sido determinada uma equação da função de classificação para cada uma das espécies. Conquanto cada uma das espécies possa ser identificada por qualquer das ferramentas utilizadas, a análise morfológica, a análise morfométrica, assim como as análises discriminante e canônica devem ser consideradas ferramentas complementares no processo de identificação das espécies, aumentando a confiabilidade da identificação. Uma grade politômica ilustrada para identificação rápida dessas espécies foi elaborada. A técnica de multiplicação in vitro dessas espécies em cilindro de cenoura mostrou-se adequada para produção massiva desses nematóides, sendo que P. penetrans e P. jaehni foram as espécies que produziram, respectivamente, o maior e o menor número de indivíduos e ovos por cilindro de cenoura, aos 120 dias após a inoculação. / The lesion nematodes (Pratylenchus spp.) are considered the second largest group of plant parasitic nematodes of economic importance in the world. The morphology and morphometry of the six more common species of these nematodes in Brazil, namely: Pratylenchus brachyurus, P. coffeae, P. jaehni, P. penetrans, P. vulnus and P. zeae, were studied at the light and scanning electron microscopes. The data were also submitted to discriminant and canonical analyses and an equation of the classification function for each one of the species was determinated. Althought each one of the species can be identified by any of the tools used, the morphologic and morphometric analyses, as well as the discriminant and canonical analyses, must be considered complementary tools in the process of species identification, thus increasing the reliability of the identification. An illustrated polytomous key for a fast identification of these species was elaborated. The in vitro multiplication technique of these species in carrot cylinder was suitable for massive production of these nematodes. Pratylenchus penetrans and P. jaehni were the species that produced, respectively, the greatest and the smallest number of individuals and eggs for carrot cylinder, 120 days after the inoculation.

La réduction du taux de cholestérol (CH) sanguin est un point clé dans la lutte contre les maladies cardiovasculaires. L’efficacité contrastée des médicaments disponibles actuellement ainsi que l’intérêt porté autour du microbiote intestinal dans la régulation de la physiologie de l’hôte nous amènent à envisager cette voie comme alternative thérapeutique. La production de coprostanol (CO), dérivé très peu absorbé du CH, par des bactéries de ce microbiote a été corrélée positivement à une faible cholestérolémie. Les objectifs de cette thèse sont i) d’isoler et d’identifier de nouvelles souches bactériennes ayant cette activité, ii) d’identifier les gènes bactériens responsables de cette transformation et iii) de détereminer l’impact de ce métabolisme sur la physiologie de l’hôte. Nous avons isolé 22 nouvelles souches productrices de CO à partir des selles d’un individu en produisant beaucoup. Nous avons choisi les souches Bacteroides sp. D8 et Bacteroides sp. BV pour la construction de deux banques génomiques et huit autres pour des essais d’implantation in vivo dans le tractus gastro-intestinal (TGI) de souris axéniques. Nous avons identifié 55 clones potentiellement positifs par le criblage fonctionnel des banques génomiques. Leurs analyses supplémentaires devraient nous apporter des informations sur les gènes impliqués dans cette activité. Toutes les bactéries sélectionnées sont capables de coloniser le TGI de la souris axénique. La souche Parabacteroides distasonis est la meilleure souche productrice de CO in vivo. Nous avons testé son effet sur la cholestéolémie chez des souris axéniques soumises à un régime riche en CH sur 11 semaines en comparaison avec une souche non productrice in vitro, B. dorei, et avec des souris conventionnalisées comme contrôle. La souche B. dorei produit du CO in vivo, soulignant l’importance de l’environnement dans l’activité de production de CO déjà supposée d’après la littérature et nos résultats in vitro. Des gènes impliqués dans l’excrétion du CH de l’organisme vers les selles sont surexprimés chez ces souris et celles colonisées avec P. distasonis. Cependant seules ces dernières présentent une cholestérolémie plus faible que les souris conventionnalisées. Le mécanisme impliqué semble indépendant de la production de CO et de l’excrétion de CH car les mêmes quantités de ces composés sont retrouvées dans les selles indépendamment du statut bactérien. Les concentrations en acides biliaires totaux dans la bile et dans les selles sont supérieures pour les souris monocolonisées comparées au conventionnalisées. Les selles des souris colonisées avec P. distasonis présentent plus d’acides urso- et chénodésoxycholiques que les souris conventionnalisées et plus d’acide cholique que les souris colonisées avec B. dorei. En conclusion, nous avons isolé de nouvelles souches et identifier des clones potentiellement positifs. Les études in vivo tendent à montrer que l’activité de production de coprostanol n’a pas d’effet sur la cholestérolémie. En revanche, la souche P. distasonis semble diminuer la cholestérolémie par un mécanisme encore inconnu. / Cholesterol (CH) level management is a keystone to limit cardiovascular diseases. The contrasted efficiency of the drugs currently available as well as the interest around the intestinal microbiota in regulating the host physiology lead us to consider this pathway as a therapeutic alternative. The production of coprostanol (CO), a very poorly absorbed CH derivative, by bacteria of this microbiota has been positively correlated with low CH plasma level. The aims of this thesis are (i) isolate and identify new bacterial strains possessing this activity, (ii) identify the bacterial genes responsible for this transformation and (iii) determine the impact of this metabolism on host physiology. We isolated 22 new strains producing CO from the stools of a high-coprostanol producing individual. We chose Bacteroides sp. D8 and Bacteroides sp. BV for the construction of two genomic libraries and eight others for in vivo implantation tests in the gastrointestinal tract (GIT) of germ-free mice. We identified 55 potentially positive clones by functional screening of these genomic libraries. Their additional analyzes should provide us with information about the genes involved in this activity. All selected bacteria are capable of colonizing the GIT of germ-free mice. Parabacteroides distasonis is the best strain producing CO in vivo. We tested its effect on blood cholesterol level in germ-free mice subjected to an 11-week CH-rich diet compared to an in vitro non-producing strain, B. dorei, and with conventionalized mice as control. The B. dorei strain produces CO in vivo, emphasizing the importance of the environment in the CO production activity already assumed from the literature and our results in vitro. Genes involved in the excretion of CH from body to feces are overexpressed in these mice and those colonized with P. distasonis. However, only the latter have lower cholesterolemia than conventional mice. The mechanism involved appears to be independent of CO production and CH excretion because the same amounts of these compounds are found in feces independently of bacterial status. Total biliary acids concentrations in bile and feces are higher for monocolonized mice compared to conventionalized mice. The feces of mice colonized with P. distasonis exhibited more urso- and chenodeoxycholic acids than conventionalized mice and more cholic acid than mice colonized with B. dorei. In conclusion, we have isolated new strains and identified potentially positive clones. In vivo studies tend to show that coprostanol production activity has no effect on plasma cholesterol. In contrast, P. distasonis seems to decrease plasma cholesterol by a still unknown mechanism.