Orientadores: Helia Harumi Sato , Lara Durães Sette / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-13T13:26:40Z (GMT). No. of bitstreams: 1 Macedo_JulianaAlves_D.pdf: 1354680 bytes, checksum: f0751667b78c8b7e3db22d9ceb16adbf (MD5) Previous issue date: 2009 / Resumo: A transglutaminase (TGase) (EC 2.3.2.13; proteina-glutamina ?-glutaminiltransferase) é uma enzima capaz de catalisar reações de transferência de grupos acil utilizando resíduos de glutamina das ligações peptídicas de proteínas como doadores de grupos acil, e diversas aminas primárias como receptores. As ligações covalentes cruzadas entre inúmeras proteínas e peptídeos pela transglutaminase promovem mudanças nas propriedades de proteínas de alimentos. Por essa razão, a transglutaminase é amplamente utilizada nas indústrias de processamento de alimentos para o desenvolvimento de novos produtos e modificação de características como: viscosidade, capacidade emulsificante e valores nutricionais. Uma cepa de Actinomyceto, isolada de amostras de solo brasileiro, foi investigada taxonomicamente por uma combinação de técnicas moleculares e morfológicas, resultando na conclusão de que a cepa pertence ao gênero Streptomyces sp. A cepa, chamada de Streptomyces sp. CBMAI 837 produziu transglutaminase quando cultivada a 30°C por cinco dias, em agitador rotatório, no meio de fermentação otimizado, composto por: 0,2% KH2PO4, 0,1% MgSO4.7H2O, 2% farinha de soja, 2% amido de batata, 0,2% glicose, e 2% peptona, atingindo uma atividade enzimática de 1,37 U.mL-1. A transglutaminase foi purificada cerca de 5 vezes através de duas passagens cromatográficas sucessivas em uma coluna de filtração em gel Sephadex G-75, com 17% de recuperação. A purificação da proteína foi comprovada por homogeneidade eletroforética em SDS-PAGE. A massa molar da TGase foi estimada em cerca de 45 kDa. A transglutaminase de Streptomyces sp CBMAI 837, tanto na forma bruta quanto purificada, apresentou atividade enzimática ótima em pH 6,0-6,5, e em 35-40°C. Um segundo pico de atividade ótima foi observado em pH 10,0 na enzima no estado bruto. Ambas as formas da enzima foram estáveis na faixa de pH de 4,5 a 8,0 e até 45°C. A transglutaminase na forma bruta e purificada mostrou-se independente de íons cálcio, mas foi ativada na presença de K+, Ba2+, e Co2+; e inibida por Cu2+ e Hg2; o que sugere a presença de um grupo tiol no sítio ativo da enzima. A TGase purificada apresentou um Km de 6,37 mM e um Vmax de 1,70 U/mL, enquanto a enzima bruta apresentou Km de 6,52 mM e um Vmax de 1,35 U/mL para o substrato N-carbobenzoxi-L-glutaminil-glicina. A influência da transglutaminase de Streptomyces sp CBMAI 837 bruta, nas propriedades de géis ácidos de caseinato de sódio foi investigada, tendo como parâmetro géis preparados com a TGase comercial (Ajinomoto Inc.). Os géis com a enzima comercial tiveram um valor de módulo de elasticidade maior, porém, dependendo da concentração de proteína, estes foram menos deformáveis. Os géis com enzima bruta de Streptomyces sp. CBMAI 837 se mostraram muito mais rígidos e menos elásticos. Resultados da eletroforese indicaram que a enzima comercial promoveu a formação de polímeros de proteínas de massa molecular mais alta do que a enzima de Streptomyces sp. CBMAI 837. Os testes de microscopia eletrônica de varredura e da capacidade de retenção de água mostraram que características particulares de cada um dos géis poderiam estar associadas ao tipo específico de interação promovida por cada uma das amostras enzimáticas testadas / Abstract: Transglutaminase (EC 2.3.2.13; protein-glutamine ?-glutaminyltransferase) is an enzyme that catalysis an acyl transfer reaction using protein or peptide-bond glutamine residues as acyl donors and several primary amines as receptors. The covalent cross-links between a number of proteins and peptides introduced by transglutaminase promote modification of the functional properties of the food proteins. Therefore, transglutaminase are widely used by food-processing industries for the purpose of new product development, modification of the product properties such as viscosity, emulsification foaming and nutritional values. An actinomycete strain, isolated from Brazilian soil, was taxonomically investigated using a combination of molecular and morphological basedmethods, resulting on the conclusion that the strain belongs to the genus Streptomyces sp. The strain, named Streptomyces sp. CBMAI 837, produce transglutaminase when cultivated at 30°C for 5 days at 200 rpm in a rotatory shaker, on the optimized fermentation medium composed of 0.2% KH2PO4, 0.1% MgSO4.7H2O, 2% soybean flour, 2% potato starch, 0.2% glucose, and 2% peptone, with a enzymatic activity of 1.37 U.mL-1. The enzyme purification was performed by of two successive chromatographies on Sephadex G-75 columns with yields of 48% and 17%, respectively. The protein purification was successfully achieved to electrophoretical homogeneity on SDS-PAGE. The molecular mass of the MTGase was estimated to be about 45 kDa. The enzyme from Streptomyces sp., in both crude and pure forms, exhibited optimal activity in the 6.0-6.5 pH range and at 35-40°C. A second maximum of activity was observed at pH 10.0 on the crude Streptomyces sp. enzyme. Both forms of transglutaminase were stable over the pH range from 4.5 to 8.0 and up to 45°C. The activities of all the TGase samples were independent of Ca+2 concentration, but they were elevated in the presence of K+, Ba2+, and Co2+ and inhibited by Cu2+ and Hg2+, which suggests the presence of a thiol group in the TGase¿s active site. The purified enzyme presented Km of 6.37 mM and Vmax of 1.7 U/mL, while the crude enzyme demonstrated Km of 6.52 mM and Vmax of 1.35 U/mL. The influence of the transglutaminase on acid-gel properties was studied. Texture parameters showed that the commercial TGase (Ajinomoto Inc.) gels had greater values of elasticity modulus and could promote the formation of more elastic and soft food systems, while addition of the crude TGase of Streptomyces sp. CBMAI 837 to the gel led to the formation of more rigid and less elastic gels. The electrophoresis showed that the commercial TG enzyme in this system promoted higher molecular mass protein polymers than the enzyme from Streptomyces sp. CBMAI 837. Microscopy and water holding capacity (WHC) observations showed that all the gel characteristics could be associated to specific interactions promoted by each TGase tested / Doutorado / Doutor em Ciência de Alimentos

Orientador: Ronaldo Aloise Pilli / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-03T17:32:11Z (GMT). No. of bitstreams: 1 CorreaJunior_IvanReis_D.pdf: 7722064 bytes, checksum: 6dc8406d34eebe08d963a2c6bdabdc09 (MD5) Previous issue date: 2003 / Resumo: A delactomicina é um policetídeo natural, isolado a partir de culturas de Streptomyces sp, que apresenta atividade inibitória da transposição de uma proteína reguladora Rev do vírus HIV -1. A estrutura planar da delactomicina foi estabelecida por métodos espectroscópicos e nenhuma menção foi feita a respeito de suas configurações relativa e absoluta. Neste trabalho, descrevemos a primeira síntese total da delactomicina e, por conseguinte, a sua elucidação estrutural. A estratégia de síntese proposta para a delactomicina foi orientada por algumas idéias centrais que visavam preservar a integridade da cetona b,g-insaturada, controlar adequadamente a geometria das ligações duplas presentes na estrutura e a estereoquímica absoluta dos centros estereogênicos, sem comprometer a eficiência da rota sintética. As etapas-chave na preparação da estrutura proposta da delactomicina foram: o acoplamento de Negishi catalisado por paládio(0) para a construção do segmento CII-CI6; a reação aldólica mediada por estanho(II), com seletividade sin, para a união dos segmentos C7C 1 O e C11-C 16; e a olefinação de Wittig para instalação do sistema diênico conjugado (E,E) através da junção da cadeia principal com os segmentos C5-C6 e CI-C4. Os dados espectroscópicos da (-)-delactomicina sintética se mostraram idênticos àqueles reportados para o produto natural, permitindo assim confirmar a sua identidade e estabelecer inequivocamente a sua configuração relativa. A indisponibilidade dos dados de rotação óptica ou dicroísmo circular para a delactomicina natural nos impossibilitou a determinação de sua estereoquímica absoluta / Abstract: The natural polyketide delactonmycin isolated from Streptomyces strains displays potent inhibitory activity of the nucleo-cytoplasmic translocation of the HIV -1 regulatory protein Rev. The planar structure of delactonmycin was established by spectroscopic methods, but its relative as well as its absolute configuration remained unknown. In this work, we describe the first total synthesis and structural elucidation of delactonmycin The synthetic approach to delactonmycin featured some key points to save the integrity of the b,g-unsaturated ketone, appropriately control configuration of the double bonds and the absolute stereochemistry of stereogenic centers, without compromise the synthetic route efficiency. The pivotal steps on the preparation of delactonmycin framework were: a palladium(0)-catalysed Negishi coupling reaction for the construction of C11-C 16 subunit; a diastereoselective tin-mediated syn-selective aldol reaction for assembling the subunits C7-ClO and C11-C16; and a Wittig olefination for the installation of the conjugated (E,E)-diene C5-C6 and C6-C7. The spectroscopic data of the synthetic (- )-delactonmycin nicely matched those reported for the natural product, allowing us to confirm their identity and unambiguously establish its configuration. Unfortunately, the lack of a sample of natural de1actonmycin or of its chiroptical data precluded the determination of its absolute configuration / Doutorado / Doutor em Quimica

Tese (livre docencia) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos e Agricola / Made available in DSpace on 2018-07-18T01:44:19Z (GMT). No. of bitstreams: 1 Park_YongKun_LD.pdf: 2198176 bytes, checksum: cd37f3df570cfe47bfdce1ec1cb2b911 (MD5) Previous issue date: 1976 / Resumo: Isolou-se da terra, 650 cepas de microrganismos e examinou-se a atividade que cada uma possuía de isomerizar d-glicose. Encontrou-se uma linhagem de Streptomyces sp, com alta atividade de produção da enzima quando incubada em meio de cultura contendo xilose como indutor. Verificou-se que esta enzima é intracelular, e a cepa em questão foi identificada como Streptomyces bikiniensis (Johnson e Waksman, 1947). Descobriu-se que a glicose isomerase de Streptomyces bikinien sis é efetivamente induzida por xilose, enquanto que xilana induz a enzima de maneira mais branda. Da mesma forma, d-Aratiino se, L-Rhamnose, d frutose, d-manose e d-ribose, produzem baixa indução da glicose isomerase. Purificou-se a glicose isomerase de Streptomyces bikiniensis por fracionamento com sulfato de amónio, DEAE-celulose e filtração com Sephadex G-200. Através de eletroforese de gel poliacrilamida, encontrou se que a enzima glicose isomerase purificada era homogênea. As propriedades cinéticas da glicose isomerase foram estudadas e os resultados obtidos, foram comparados com a glicose isomerase produzida nos outros microrganismos. Verificou-se também, que os substratos adequados para a enzima, são: d-xilose, d-ribose e d-glicose, com os respectivos valores de Km: 0,07, 0,11 e 0,26 M. Esta enzima, mostrou possuir maior afinidade para xiiose do que para ribose ou glicose. O peso molecular da enzima foi calculado por eletroforese de gel de SDS-poliacrilamida e encontrou-se ser 52.000, A influência do pH sobre a atividade enzimática, foi verificada usando-se tampão fosfato e tampão tris, Encontrou-se que o pH ótimo para esta enzima se encontra entre S e 9, Verificando-se a atividade enzimática em diferentes temperaturas, - descobriu-se que sua temperatura ótima é de 80°C. Esta enzima é altamente termoestável. 0 estudo sobre o efeito de íons metálicos sobre a atividade da isomerase de Streptomyces bikiniensis, mostrou que a isomerizaçao de glicose foi altamente ativada por Mg2+ e Co2+ , e que sofreu baixa ativação com Mn2+ e Ni2+. Cobalto, manganes e magnésio, ativaram efetivamente a isomerização de xilose e de ribose.Observou-se também, que cobalto e Mg2+, inibiram a desnaturação térmica da enzima. Descobriu-se ainda, que glicose isomerase também isomeriza eficaznente d-xilose e d-ribose, e, em menor extensão, L-ranno se e d-arabinose para suas respectivas cetoses. A glicose isomerase de Streptomyces bikiniensis foi testada - para a isomerização de glicose a frutose, incubando-se uma mistura da enzima e varias concentrações de glicose em tampão fosfato 0,05 M, pH 2, contendo 5 mg MgSO4 e 0,05 mM CoCl2, a várias temperaturas. Verificou-se que a isomerização máxima de glicose a frutose ($0%), deu-se incubando-se a 70°C por T) horas, em concentração de enzima e substrato adequados / Abstract: Six hundred fifty strains of microorganisms were isolated from soil and screened for d-glucose isomerizing activity. It was found that a strain of Streptomyces sn. produced high activity of glucose isomerizing enzyme in culture medium containing xylose as inducer. The glucose isomerizing enzyme was in tracellular enzyme. This strain was identified as Streptomyces bikiniensis (Johnstone and Waksman, 1947). It was found that xylose effectively induced glucose isomers, se of S. bikiniensis and to a lesser extent, xylan. d-Arabinose. L-Rhannose, d-frutose, d-Mannose and d-ribose also induced slightly the enzyme. The glucose isomerase of S. bikiniensis was purified by fractionation with ammonium sulfate, DEAE cellulose column - chromatography and gel filtration on Sephadex G-200. The purified glucose isomerase was found to be homogeneous by poly_ acrylamide gel electrophoresis. Kinetic properties of purified glucose isomerase were studied and the results were compared with glucose isomerase from other strains of microrganism. D-Xylose, d-Ribose and d-glucose served as effective substrates for the enzyme with respective Km values of 0,07, 0,11 and 0,26 M. This enzyme exhibits greater affinity for xylose than for ribose or glucose. Molecular weight for the enzyme was measured by SDS-polyacryl amide gel eletrophoresis and found to be 52.000. The effect of pH on enzyme activity was examined in posphate buffer and tris buffer and the optimum pH was between 8 and 9. The enzyme activity at various temperatures was examined and- the optimum temperature was found to be 80°C. The enzyme was highly thermostable. The effect of metal ions on S. hikiniensis isomerase activity shows that isomerization of glucose was activated most effectively by Mg2+and Co2+, and slightly by Mn2+ and Ni2+. Isomerization of ribose was also activated effectively by Mg2+ 'Mn2+ and Co2+. Cobalt and Mg2+ also inhibited thermal denaturation of the enzyme. It was found that the glucose isomerase also effectively iso- merizes d-xylose and d-ribose, and to a lesser extent L-rham- nose and d-arabinose to their respective ketoses. The glucose isomerase from S. bikiniensis was examined for isomerization of glucose to fructose in batch system by incubating a mixture o£ the enzyme and various concentrations of glucose in 0,05 .M phosphate buffer, pH 7,2 containing 5 mM MgSO4 and 0,5 mM CoCl2 at various temperatures. It was found-that maximum isomerization of glucose to fructose (50%) was reached when optimum concentration of enzyme and substrate was incubated at 70°C for 70 hours / Tese (livre docencia) - Univer / Livre Docente em Engenharia de Alimentos

Ingeniería en Biotecnología Molecular / Actualmente, el uso de enzimas corresponde a un área de la biotecnología de gran crecimiento y desarrollo, la cual ha buscado dar solución a problemas de tipo industriales, biomédicos y domésticos; representando una solución específica, sustentable y ecológicamente amigable. En el ámbito de la innovación, como parte de una mejora tecnológica se ha buscado obtener enzimas estables y que puedan ser utilizadas en condiciones extremas de pH, temperatura, salinidad etc. Los microorganismos provenientes de ambientes extremos representan una buena fuente de este tipo de enzimas, ya que generalmente estos microorganismos precisan de este tipo de enzimas para la sobrevida en las condiciones hostiles de su hábitat. Un ambiente extremo que ha sido poco explorado en este sentido es el Desierto de Atacama. Conocido por ser el desierto más antiguo y árido del planeta, presenta condiciones ambientales que hacen que sea considerado como un ambiente extremo único en el mundo. Pese a estas condiciones adversas, diversos microorganismos han podido ser aislados desde este ambiente tan particular. Entre ellos esta Streptomyces leeuwenhoekii C34 que presenta varios grados de tolerancia a condiciones extremas. En este trabajo se realizó la búsqueda bioinformática de enzimas de interés comercial en el genoma de S. leeuwenhoekii C34. Teniendo en cuenta el gran potencial biotecnológico y diversidad de aplicaciones de las enzimas lipasas, se seleccionó el gen sle_62990 que codifica para una lipasa putativa GDSL- SGNH. Con el fin de estudiar este gen se generó la cepa LIP de S. leeuwenhoekkii C34 que sobre expresa el gen sle_62990. Con esta cepa se pudo comprobar que el gen sle_62990 codifica para una lipasa extracelular funcional y que presenta actividad contra p-nitrofenil palmitato. También se intentó la expresión heteróloga de la enzima en el medio intracelular de E. coli. Sin embargo, no se obtuvieron los resultados esperados, ya que se encontró en cuerpos de inclusión. / Currently, the use of enzymes corresponds to a growing area in the biotechnology field which has sought to solve industrial, biomedical, and domestic problems. These represent a specific, sustainable and ecologically friendly solution. Stable enzymes that can be used under extreme conditions such as high pH, temperature and salinity are of particular interest for biotechnological improvement. Microorganisms from extreme environments require these types of enzymes in order to survive under the harsh conditions of their habitat. Therefore, they represent a good source of interesting enzymes. An extreme environment that has been little explored is the Atacama Desert. The Atacama Desert is known as the oldest and driest desert on Earth. It presents extreme a environmental conditions. Despite these harsh conditions, various microorganisms have been isolated from this particular environment. Among them Streptomyces leeuwenhoekii C34, that shows several degrees of tolerance to extreme conditions. In this work, possible commercial enzymes were searched in the genome of S. leeuwenhoekii C34. Considering the great biotechnological potential and the diversity of applications of the lipases enzymes the gene sle_62990 that encoded for a putative lipase was selected. In order to study this gene, the LIP strain of S. leeuwenhoekii C34 that over-expressed the sle_62990 was generated. The over-expression allowed to confirm that the sle_62990 gene encodes for a functional extracellular lipase and it has activity against p-nitrophenyl palmitate. Attempts to heterologously express this gene in E. coli were unsuccessful.

No description available.

Développé dans le contexte mondial de lutte aux souches microbiennes résistantes aux antibiotiques, ce projet de maîtrise a pour but d’isoler et de caractériser un opéron de synthèse d’une molécule naturelle potentiellement bioactive, un tétramate polycyclique macrolactame (PTM), provenant d’une souche de streptomycète peu caractérisée mais dont le génome a été récemment séquencé. L’objectif principal est de transférer l’opéron dans une souche spécialisée de Escherichia coli pour son expression et sa caractérisation. Nous avons observé que la souche d’intérêt, Streptomyces fulvissimus ATCC27431 / DSM40593, produisait effectivement une molécule capable d’inhiber la croissance d’une levure. Nous n’avons cependant pas été en mesure de réaliser l’isolation et le transfert hétérologue de l’opéron, malgré l’utilisation de trois approches différentes. La première approche consistait à obtenir directement les gènes de l’opéron via une amplification PCR à partir d’ADN génomique de S. fulvissimus. La seconde approche comportait l’assemblage de gènes synthétisés chimiquement pour reconstituer l’opéron sur deux plasmides. La dernière approche impliquait la création puis le criblage d’une librairie d’ADN génomique de S.fulvissimus basée sur le fosmide pCC1FOS dans l’hôte E. coli. Les résultats inattendus issus du séquençage de quelques fosmides ont justifié le séquençage complet de l’ADN génomique de la souche ATCC 27431 / DSM 40593. Les contigs obtenus montrent que notre souche diffère de la souche de S. fulvissimus dont le génome a été publié, ce qui suggère que le génome publié a été incorrectement associé à cette souche. Nos résultats montrent également que l’opéron de biosynthèse du PTM n’est pas présent, en tout ou en partie, dans ces contigs et que ces derniers ne s’alignent pas parfaitement avec l’ADN d’aucune souche connue de streptomycète, ce qui implique que nous avons séquencé, pour la première fois, l’ADN de cette souche de S. fulvissimus. L’analyse bio-informatique des contigs nous a permis de mettre en évidence chez cette bactérie des voies de biosynthèse de molécules naturelles potentiellement bioactives qui pourraient être d’intérêt pour des études futures. / In the context of the worldwide fight against drug-resistant microbes, this project aims to isolate and characterize a putative gene cluster for the synthesis of a bioactive molecule, a polycyclic tetramate macrolactam (PTM), from a poorly characterized but recently sequenced strain of Streptomyces1 . The main goal is to transfer the gene cluster in a specialised strain of Escherichia coli for its expression and characterization. We observed that the strain of interest, identified as Streptomyces fulvissimus DSM 40593 / ATCC 27431, indeed synthesized a molecule capable of inhibiting the growth of yeast. However, we have not been able to isolate or transfer the gene cluster even though we employed three different strategies. The first strategy involved PCR amplification of the gene cluster directly from S. fulvissimus’ genomic DNA. The second strategy involved the chemical synthesis and enzymatic assembly of the gene cluster on two plasmids. The final strategy involved the construction and screening of a S. fulvissimus genomic DNA library with the pCC1FOS fosmid in the E. coli host. DNA sequencing of a few fosmids generated unexpected results and justified the sequencing of the complete genome of Streptomyces fulvissimus ATCC 27431 / DSM 40593. The assembled DNA contigs differed from the sequence of the Streptomyces strain whose genome was previously published and suggest that the latter was probably mislabeled. Our contigs show that the PTM biosynthetic gene cluster is absent from our strain’s genome, and they do not align perfectly with the sequence of any published genome, which suggests that we sequenced the genome of the S. fulvimissus strain ATCC 27431 / DSM 40593 for the first time. Bioinformatics analysis allowed the detection of genes potentially involved in the biosynthesis of bioactive molecules that could be of interest in future studies.

No description available.

The increasing emergence of antibiotic resistant strains of bacteria and fungi is driving the need to increase the production of current antibiotics and produce novel antimicrobial compounds. This study worked to increase the production of cycloheximide and streptomycin antibiotics by co-culturing Streptomyces griseus with other industrially important microbes. 1-3 industrial challenge microbes at a time were added to a culture of S. griseus and allowed to grow for one week in shake flask cultures before harvesting and quantifying antibiotic production. Fifteen different industrial challenge microbes placed in 35 different combinations were used in the study and 17 of these combinations were found to significantly increase antibiotic production after analysis with ANOVA. Antibiotic production was confirmed using bioautograms. Three of the successful different co-cultures were then subjected to a study to see when industrial challenge microbe addition was optimal. Results suggest that the optimal time to add the challenge microbes was 1-3 days following the original S. griseus inoculation. Dead challenge microbes were also added to a culture of S. griseus and it was found that these significantly increased cycloheximide as much as the live co-cultures did. / Department of Biology

L’agent phytopathogène Streptomyces scabiei est une bactérie du phylum actinobactérie présent dans les sols à travers le monde. S. scabiei est l’agent principal responsable de la gale commune de la pomme de terre. Cette maladie est coûteuse pour les producteurs de la pomme de terre. En effet, la pomme de terre va perdre sa valeur commerciale lorsque la bactérie attaque le périderme du tubercule et provoque des lésions liégeuses en surface ou plus ou moins en profondeur. C’est dans le périderme de la pomme de terre que la subérine va se déposer pour protéger le tubercule des agressions biotiques. Des études antérieures ont mis en évidence le rôle de la subérine comme inducteur de la production de thaxtomine A (phytotoxine essentielle à la virulence) chez S. scabiei. De même, la subérine va induire chez S. scabiei, la sécrétion d’enzymes dégradant les parois végétales, en particulier des glycosyl hydrolases, dont des cellulases. Cette thèse vise à élucider les mécanismes impliques dans la production de cellulases chez la souche S. scabiei EF-35. Dans un premier temps, le sécrétome de S. scabiei ayant poussé en présence de subérine et cellulose, soit avec un seul des deux polymères, a été analysé. Ces analyses du sécrétome ont révélé que l’addition de subérine dans un milieu contenant de la cellulose induisait une surproduction de glycosyl hydrolases. L’induction des enzymes cellulolytiques par la subérine, correlait avec la présence d’un inhibiteur de subtilase (SCAB_8801) qui pourrait jouer un rôle dans la différenciation cellulaire et le métabolisme secondaire. Ces résultats ont permis d’avancer un modèle dans lequel la subérine et le cellobiose jouent conjointement un rôle pour activer les mécanismes de virulence de la bactérie. Dans un deuxième temps, nous avons voulu savoir si le cellobiose (la molécule résultante de la dégradation de la cellulose) induisait des enzymes cellulolytiques chez S. scabiei, mais aussi chez deux autres espèces de Streptomyces pathogènes et une espèce de Streptomyces non pathogène. L’activité cellulolytique de S. scabiei en présence de subérine est beaucoup plus importante que lorsque la bactérie est en présence de cellobiose (de cinq à dix fois supérieure). De même, la présence de subérine dans le milieu de culture de S. scabiei augmente l’expression rélative des gènes des cellulases. Les deux autres Streptomyces pathogènes (S. acidiscabies et S. turgidiscabies) exhibent un profil contraire à S. scabiei. En effet, S. acidiscabies et S. turgidiscabies affichent une activité cellulolytique et une expréssion rélative des gènes de cellulases plus importante dans le milieu supplémenté de cellobiose que dans le milieu supplémenté de subérine. Streptomyces scabiei semble donc mieux adaptée que les autres espèces de Streptomyces à dégrader le matériel cellulosique encastré dans les parois subérisées du périderme. Les résultats présentés dans cette thèse visent à apporter des éléments de réponse pour mieux comprendre les interactions S. scabiei – pomme de terre. Ainsi, les biopolymères retrouvés dans la pomme de terre (subérine et cellulose) vont jouer un rôle crucial dans la virulence de l’agent phytopathogène. Cependant, il semblerait que S. scabiei s’est spécialisé au cours du temps à coloniser son hôte, la pomme de terre. La subérine induit la production de cellulases chez S. scabiei mais pas chez les autres deux Streptomyces pathogènes testés (S. acidiscabies et S. turgidiscabies). Ceci nous laisse penser que la subérine est impliquée dans des mécanismes qui restent encore à élucider.

The purpose of this investigation is to attempt to learn something of the biochemical ecology of volatile substances produced by actinomycetes.