BTX biodegradation rates, biochemical expression patterns and microbial ecology were studied under anoxic (denitrifying), anoxic/microaerobic/aerobic, and anoxic/microaerobic conditions in activated sludge sequencing batch reactors. The studies showed that toluene and m-xylene were denitrified via benzoyl-CoA reductase. Although benzene, o-, and p-xylene were recalcitrant under denitrifying conditions, they were biodegraded under microaerobic (< 0.2 mg/L dissolved oxygen) and nitrate or nitrite (NOx)-supplemented microaerobic conditions. The patterns of the specific enzymes associated with BTX biodegradation under microaerobic conditions indicated that the three compounds were metabolized by oxygen-dependent pathways. The expression levels of catechol 1, 2-dioxygenase and catechol 2, 3-dioxygenase under microaerobic conditions were induced to levels as high as under aerobic conditions (> 4 mg/L dissolved oxygen). Benzene, o-, and p-xylene biodegradation rates were twice as fast under NO_x-supplemented compared to NO_x-free microaerobic conditions, and the specific biodegradation rates under aerobic and NO_x-supplemented microaerobic conditions were comparable. 16S rRNA probes targeting representative toluene-degraders were used to investigate the microbial communities in the three sequencing batch reactors by using a dot blot hybridization technique. The hybridization results suggest that multiple redox environments fostered a more diverse microbial community and the activities of the target organisms in the reactors with multiple redox environments were higher than in the single redox reactor. Additionally, facultative toluene-degraders appeared to play a less significant role than the strict anoxic and aerobic toluene-degraders in all three SBRs. / Ph. D.

In my diploma thesis I observed microbial activity in Miocene sediments collected at two different depths - 30 and 150 meters - in the "Družba" open-mine pit, which is located in Sokolov Brown Coal Basin. There were three different types of sediment: lamellar, amorphous and transitional. Samples were obtained under sterile conditions and following treatments were applied to the transitional sediment: addition of glucose, wetting and freezing. The aim of my study was to observe the activity of the original microflora at various depths and the impact of environmental factors that can affect the quarried claystones after being put on heaps. Microbial activity was evaluated by measuring released CO2 (titration). Obtained values of microbial activity did not show any differences between the respiration of sediments of different ages (depths), but differences between different types of sediments were significant, the highest values were found in lamellar sediment. Affection of samples then showed biota activity response suggesting that microbial communities at lower depths are limited by nutrients. Because the application of glucose did not show any noteworthy effect, we can assume that these communities are specialize on present fossil organic matter they are able to decompose, which is important especially in...

Submitted by Ana Damasceno (ana.damasceno@unipampa.edu.br) on 2017-05-12T17:36:02Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Caracterização química, atividades antioxidante, antileucêmica e antimicrobiana da própolis âmbar sul brasileira.pdf: 1920627 bytes, checksum: a4863fc2a0ca638e21de691cb6125515 (MD5) / Made available in DSpace on 2017-05-12T17:36:02Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Caracterização química, atividades antioxidante, antileucêmica e antimicrobiana da própolis âmbar sul brasileira.pdf: 1920627 bytes, checksum: a4863fc2a0ca638e21de691cb6125515 (MD5) Previous issue date: 2017-03-27 / A própolis é um composto utilizado pelas abelhas, com a finalidade de vedar a colmeia e evitar contaminações, que se destaca por suas atividades biológicas as quais têm sido muito estudadas para fins terapêuticos. Quando produzida por abelhas da espécie Apis mellifera a substância é composta por cerca de 50 % de resina vegetal misturada a enzimas presentes em sua saliva e cera. Este produto natural pode variar dependendo da origem botânica/geográfica e mais de 300 compostos já foram descritos. No caso do Brasil, existe grande variabilidade da composição química que é facilmente explicada pela sua grande biodiversidade. O objetivo deste trabalho foi analisar o perfil químico e as atividades antioxidante, antileucêmica e antimicrobiana da própolis de São Gabriel/Rio Grande do Sul, a qual denominamos própolis Âmbar, e comparar suas propriedades com as própolis brasileiras Vermelha e Verde. As análises do perfil químico foram realizadas pelas técnicas de GC-MS, HPLC e quantificação dos flavonoides e fenóis totais. A atividade antioxidante foi aferida pelas técnicas DPPH°, ABTS°+ e FRAP. A atividade antileucêmica foi analisada nas linhagens celulares K562, Jurkat e U937 pelos parâmetros de IC50, viabilidade, apoptose e ciclo celular. E a atividade antimicrobiana foi analisada aferindo-se o crescimento das espécies E. coli e S. aureus. Os resultados obtidos da análise por GC-MS das própolis Âmbar, dos dois anos coletados, identificam um total de 99 compostos dentre os quais apenas 16 foram identificados para as própolis Verde e Vermelha. Também foi possível notar que grande parte dos compostos encontrados são descritos para o gênero Eucalyptus que parece ser uma fonte vegetal importante para a produção da própolis Âmbar. Quanto aos fenóis totais, flavonóides totais e atividade antioxidante, as própolis apresentaram resultados diferentes entre si, sendo os valores obtidos para a própolis Âmbar sempre menores que os encontrados para as própolis Verde e Vermelha. Porém quanto à atividade antileucêmica a própolis Âmbar apresentou resultados similares a própolis Vermelha nas análises de IC50 e viabilidade. E na análise do efeito antimicrobiano todas as própolis igualaram seu efeito em concentrações acima de 500 µg/mL, apresentando também atividades semelhantes no tratamento com E.coli na concentração de 100 µg/mL. Tipificação, identificação da origem geográfica/botânica e quantidade de estudos sobre suas atividades biológicas agregam valor à própolis. Esperamos com este trabalho expandir o conhecimento técnico-científico da própolis Âmbar contribuindo com o desenvolvimento regional e ampliando o conhecimento sobre própolis. / Propolis is a compound used by bees to seal the hive and prevent contamination that stands out because of its biological activities which have been studied for therapeutic purposes. When produced by Apis mellifera bees specie the substance is composed by about 50% vegetable resin mixed with enzymes present in its saliva and wax. This natural product may vary depending on the botanical/geographical origin and more than 300 compounds have already been described. In Brazil there is a great variability of chemical composition that is easily explained by the Brazilian biodiversity. The goal of this work was to analyze the chemical profile and antioxidant, antileukemic and antimicrobial activities of São Gabriel/Rio Grande do Sul propolis, which we call Amber propolis, and to compare its properties with the Brazilian propolis Red and Green. The chemical analyzes were performed by total flavonoids and total phenols quantification, GC-MS and HPLC. The antioxidant activity was measured by DPPH°, ABTS°+ and FRAP techniques. The antileukemic activity was analyzed in the K562, Jurkat and U937 cell lines taken into account IC50, viability, apoptosis and cell cycle parameters. The antimicrobial activity was analyzed by E. coli and S. aureus growth. The results obtained from the GC-MS of Amber propolis, collected in two years, identified a total of 99 compounds among, from these only 16 were identified for the Green and Red propolis. It was also possible verify that most of the compounds found are described for the genus Eucalyptus which seems to be an important source of compounds for the Amber propolis production. Values for total phenolics, total flavonoids and antioxidant activity, were different among the propolis, being the values obtained for the Amber propolis always smaller than those found for the Green and Red propolis. However, regarding the antileukemic activity, the propolis Amber presented similar results to the Red propolis for IC50 analyzes and viability. In the analysis of the antimicrobial effect, all the propolis presented similar effects above 500 μg/mL and also presenting some levels of activity at 100 μg / mL in E. coli. Typification, identification of the geographical/botanical origin and quantity of studies on its biological activities add value to propolis. We hope with this work to expand the technical-scientific knowledge of propolis Amber contributing to regional development and expanding knowledge about propolis.

Submitted by Mario BC (mario@bc.ufrpe.br) on 2017-03-10T14:09:02Z No. of bitstreams: 1 Jamilly Alves de Barros.pdf: 1194573 bytes, checksum: 75742892e248d2018b9529d59b784af4 (MD5) / Made available in DSpace on 2017-03-10T14:09:02Z (GMT). No. of bitstreams: 1 Jamilly Alves de Barros.pdf: 1194573 bytes, checksum: 75742892e248d2018b9529d59b784af4 (MD5) Previous issue date: 2016-02-23 / Natural ecosystems have suffered great human interventions and one of them is the conversion of forests into agricultural land, and the TDF (FTS) one of the most affected in the world. Changes in land use can be reflected by biological, biochemical, chemical and physical parameters, the first two being the fastest and most sensitive to changes in soil quality. This study evaluated how the conversion of FTS in pasture with different levels of conservation acts on the community and microbial activity in Neossolos Regolíticos. The characterization of the microbial community and enzymatic activities of sandy soils of the semiarid region of Pernambuco in areas of drought and forest disturbed. In the first chapter, the study was conducted in the city of Saint John and the selected areas were: FTS = dry tropical forest, PP = preserved and PD = degraded pasture pasture. In the second chapter were selected five cities of Pernambuco semiarid region, which were collected two composite soil samples, one in FTS and another in area with human intervention. For Chapter 1 were determined analysis of the microbial biomass carbon (MBC), total organic carbon (TOC), the fatty acid profiles of the microbial community (FAMEs) and absolute and specific enzymatic activities. In chapter 2 were determined profiles of fatty acids and enzymes absolute. FTS conversion to pasture with different levels of conservation affected the microbial community and enzymatic activities of Entisol. And the type of vegetation is shown as one of the main factors responsible for the variation of the microbial community. Quantification of FAMEs in different areas analyzed demonstrated that populations of fungi are sensitive to changes in land use that bacterial populations, because these showed a faster metabolism, ie, unable to adapt to disturbances in the ecosystem. The evaluation of specific enzymes showed how these are influenced by the TOC and MBC, where enzymes by CBM unit expressed higher values. / Os ecossistemas naturais vêm sofrendo grandes intervenções humanas e uma delas é a conversão de florestas em terras agrícolas, sendo as florestas tropicais secas (FTS) uma das mais afetadas no mundo. Alterações no uso do solo podem ser refletidas por parâmetros biológicos, bioquímicos, químicos e físicos, sendo os dois primeiros os mais rápidos e sensíveis a alterações na qualidade do solo. O presente trabalho avaliou como a conversão de FTS em pasto com diferentes níveis de conservação age sobre a comunidade e atividade microbianas em Neossolos Regolíticos. A Caracterização da comunidade microbiana e atividades enzimáticas de solos arenosos do Semiárido de Pernambuco em áreas de floresta seca e antropizada. No primeiro capítulo, o estudo foi realizado no município de São João e as áreas selecionadas foram: FTS=floresta tropical seca, PP= pasto preservado e PD= pasto degradado. No segundo capítulo foram selecionadas 5 cidades do semiárido pernambucano, onde foram coletadas duas amostras compostas de solo, uma em FTS e outra em área com intervenção antrópica. Para o capítulo 1 foram determinadas as análises do carbono da biomassa microbiano (CBM), o carbono orgânico total (COT), os perfis de ácidos graxos da comunidade microbiana (FAMEs) e atividades enzimáticas absolutas e específicas. No capítulo 2 foram determinados os perfis de ácidos graxos e as enzimas absolutas. A conversão de FTS em pasto com diferentes níveis de conservação afetou a comunidade microbiana e as atividades enzimáticas de Neossolo Regolítico. Sendo que o tipo de vegetação se mostrou como um dos principais fatores responsável pela variação da comunidade microbiana. A quantificação do FAMEs nas diferentes áreas analisadas demonstrou que as populações de fungos são mais sensíveis a alterações no uso do solo que as populações bacterianas, devido estas apresentaram um metabolismo mais rápido, ou seja, conseguirem se adaptar a perturbações no ecossistema. A avaliação das enzimas específicas mostrou o quanto estas são influenciadas pelo COT e CBM, onde as enzimas por unidade de CBM expressaram valores mais elevados.

Orientador: Ely Nahas / Banca: Lucia Helena Sipauba Tavares / Banca: Elcio Liborio Balota / Resumo: A rotação de culturas é um processo de cultivo que pode modernizar e aumentar o rendimento da atividade agropecuária de forma sustentável agregando maior qualidade ao solo. Os objetivos deste estudo foram: (I) avaliar o efeito dos sistemas culturais em plantio direto conduzidos em rotação de culturas e monitorar as alterações das propriedades microbiológicas bioindicadoras da qualidade do solo; (II) investigar as mudanças bioquímicas nos solos decorrentes da adição de diferentes tamanhos de resíduos de soja e milho durante o período de incubação. Foram determinados as biomassas microbianas- C, N e P (CBM, NBM e PBM, respectivamente), a atividade respiratória (C-CO2) e das enzimas desidrogenase, fosfatase e urease, conteúdo do carbono orgânico (Corg), carbono solúvel (Csol), fósforo orgânico (Porg), matéria orgânica (MO), potencial de mineralização do N. O quociente metabólico (qCO2) e microbiano (qMIC) do solo foram calculados. Experimento (I): A avaliação foi realizada em amostras de solo coletadas após a colheita das culturas de verão do ano agrícola 2007/2008, na camada de 0-0,15 m de profundidade em um experimento conduzido sob sistema de semeadura direta, por seis anos. O delineamento experimental foi em blocos casualizados com esquema de faixas com três repetições. As sequências utilizadas foram as monoculturas de soja (Glycine max L.) (SS) e de milho (Zea mays L.) (MM) e a rotação de culturas soja/milho (SM). As culturas de inverno foram milho, girassol (Helianthus anuus L.), nabo forrageiro (Raphanus sativus L.), milheto (Pennisetum americanum (L.) Leeke), guandu (Cajanus cajan (L.) Millsp), sorgo (Sorghum bicolor (L.) Moench) e crotalária (Crotalária juncea L.). O conteúdo da biomassa microbiana-C, N e P do solo aumentou significativamente... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Crop rotation is a practice of growing dissimilar plants that can modernize and increase the farm economy in a sustainable form for adding more quality to the soil. The aims of this study were: (I) evaluate the effect of crop sequences under no-tillage systems on changes in the soil microbiological properties; (II) investigate the biochemistries changes during the incubation of the soil added with different sizes particles of soybean and corn. There were determined the contents of microbial biomass-C, N and P, the production of C-CO2, the activities of the enzymes dehydrogenase, urease and phosphatase, the organic carbon (Corg), soluble carbon (Csol), organic phosphorous (Porg) and organic matter (MO) contents and the potential of mineralization N. The soil metabolic (qCO2) and microbial (qMIC) quotients were calculated. Experiment (I): The evaluation was performed in soil samples collected after the summer crops harvest, on 2007/2008 growing season, at 0-0.15 m soil depth layer on an experiment conducted under no-tillage system through six years. The experimental had a completely randomized block design, in strips plots with three replications. The crop sequences were continuous soybean (Glycine max L.) (SS), continuous corn (Zea mays L.) (MM), and crop rotation soybean/corn (SM). Winter crops were corn, sunflower (Helianthus anuus L.), radish (Raphanus sativus L.), pearl millet (Pennisetum americanum (L.) Leeke), pigeon pea (Cajanus cajan (L.) Millsp), grain sorghum (Sorghum bicolor (L.) Moench) and sunn hemp (Crotalária juncea L.). The content of microbial biomass-C, N and P in the soil increased significantly in crop sequence SM compared to continuous crop. The interactions SM-millet and MMsorghum influenced the content of biomass-C, SM-hemp and SM-millet in the biomass-N content... (Summary complete electronic access click below) / Mestre

Microorganisms have played a critical role in geological processes and in the formation of soils throughout geological time. It is hypothesized that biological activity can also affect soil properties in short engineering time-scales. Bioactivity in sediments is determined by the classical limiting factors (i.e., nutrients, water, C for biomass, temperature and pH) as well as by pore-size geometrical limits and mechanical interactions between bacterial cells and soil particles. These constraints restrict the range of grain size and burial depth where biomediated geochemical processes can be expected in sediments, affect the interpretation of geological processes and the development of engineering solutions such as bioremediation. When biological, geometrical and mechanical limiting factors are satisfied, bioactivity can be designed to alter the mechanical properties of a soil mass, including lowering the bulk stiffness of the pore fluid through controlled gas bio-generation, increasing the shear stiffness of the soil skeleton by biomineralization, and reducing hydraulic conduction through biofilm formation and clogging. Each of these processes can be analyzed to capture the bio-chemo-hydro-mechanical coupling effects, in order to identify the governing equations that can be used for process design. Design must recognize the implications of spatial variability, reversibility and environmental impacts.

Using mixed-culture fermentation, the carboxylate platform produces carboxylic acids, which are chemically converted into chemicals and fuels. To optimize the mixed-acid fermentation, different bioreactor configurations and operating modes were investigated. Intermittent air exposure did not affect fermentation performance and bacterial profiles, but reduced the high-molecular-weight carboxylic acids. The microbial flora contained strict and facultative microbes, suggesting the presence of a facultative anaerobic community existing in a biofilm. Compared to countercurrent trains, propagated fixed-bed fermentations have similar selectivity and acid distribution, but lower yield, conversion, productivity, and acid concentration. One- to six-stage countercurrent fermentations were operated with similar conditions. Fewer stages increased conversion, whereas more stages increased acid concentration and selectivity. One to four stages achieved similar yield, and four to six stages achieved similar maximum acid concentration. Maximum conversion was achieved with a single stage. Recycling residual biomass retained microorganisms and nutrients and increased yield and productivity. Relative to lower biomass reflux, higher reflux increased conversion, decreased selectivity, and did not affect yield. The recommended carbon-nitrogen ratio is ~24 g carbon/g nitrogen. In four-stage fermentations, recycle to the second fermentor and in parallel to the first three fermentors was optimal. Fermentations with excess or insufficient nitrogen had higher selectivity, but decreased yield and conversion. The glucose-utilization assay is a rapid and repeatable method for determining the amount of microbial activity in a sample. This method determined ~25% efficiency of a new cell separation method. In continuous fermentation, compared to no cell recycle, recycling cellular biomass increased selectivity and yield, but decreased conversion. Compared to lower cell reflux, higher reflux increased productivity, yield, and conversion, but decreased selectivity. Compared to residual biomass recycle, cell recycle had increased selectivity and yield, but decreased conversion. A new method to screen and rank inoculum sources from natural environments was successfully developed and tested.

No description available.

Made available in DSpace on 2016-06-02T18:57:28Z (GMT). No. of bitstreams: 1 2491.pdf: 971002 bytes, checksum: 1c30ad7bd5beabc3642c702b6b83f1b9 (MD5) Previous issue date: 2009-03-26 / The objective of this work was to evaluate the effect of fish hydrolysed in soil suppression against ginger yellow caused by Fusarium oxysporum f. sp. zingiberi, in a property in Tapirai, SP with no use of fungicides. Fish hydrolysed was applied directly in the soil at 0, 500, 1000, 2000 e 4000 l/ha in two different periods. The development and productivity of plants, microbial soil activity (carbon of microbial biomass, respiration, hydrolise of fluorescein diacetate, and fungi and bacteria populations) and disease incidence was evaluated 10, 70, 140, 190, and 240 days after the first application, except productivity. There were no effects of fish hydrolyzed on plant development, yield, and microbiological activity. On the other hand, it was observed a reduction in the incidence of Fusarium, when the fungus was isolated from rhizomes in petri dish and selective media. The price reduction of ginger in the local market at the last two year and the increase of disease incidence, associated with the cost of control, led the growers to a severe reduction of capitalization and disappointment with the future of the agriculture in the region. / O objetivo do presente estudo foi avaliar o potencial do hidrolisado de peixe em induzir a supressividade do solo ao amarelo do gengibre, causado por Fusarium oxysporum f. sp. zingiberi, em uma propriedade localizada no município de Tapiraí, SP, onde o cultivo é realizado sem o uso de fungicidas. Para tanto, foram aplicados ao solo 0, 500, 1000, 2000 e 4000 l/ha do hidrolisado de peixe, em duas épocas, sendo avaliado o desenvolvimento e a produtividade das plantas, a atividade microbiana do solo (carbono da biomassa microbiana; respiração; hidrólise de diacetato de fluoresceina e comunidade de fungos e bactérias) e a incidência da doença, com exceção da produtividade, as demais avaliações foram realizadas após 10, 70, 140, 190 e 240 dias da primeira aplicação do produto. Não houve efeito do hidrolisado de peixe no desenvolvimento, produtividade e qualidade do gengibre, nem na atividade microbiana do solo. Por outro lado, foi observada uma redução na recuperação de Fusarium dos rizomas do gengibre, quando do plaqueamento em meio de cultura seletivo. O preço do gengibre nos últimos dois anos e o aumento da incidência da doença, bem como o custo de controle, levou os agricultores à descapitalização e descrédito quanto ao futuro da cultura/atividade agrícola na região.

Les modèles disponibles prévoient que le changement climatique entrainera de plus longues périodes de sécheresse et/ou une diminution globale des précipitations en région méditerranéenne. Ces changements affecteront probablement la composition des communautés, la biodiversité et les processus écosystémiques. Cependant, les effets de la biodiversité, des changements de précipitations et de leurs interactions sur le fonctionnement des écosystèmes restent mal connus. Dans cette thèse, j’ai cherché à quantifier le rôle de la diversité des plantes dans la réponse d’un écosystème de garrigue méditerranéenne à une diminution de la disponibilité en eau, avec un intérêt particulier pour les processus souterrains, tels que le fonctionnement de la communauté microbienne du sol et les réponses fonctionnelles des racines.Afin d’étudier les conséquences d’une sécheresse sévère répétée sur la croissance végétale, et particulièrement racinaire, j’ai mis en place une expérience en rhizotrons, en conditions semi-contrôlées. Dans chaque rhizotron ont été plantées deux individus d’une même ou de différentes espèces des trois espèces dominantes de notre site d’étude (Quercus coccifera, Cistus albidus, Brachypodium retusum). Les sécheresses sévères répétées ont eu un effet négatif sur la survie des deux espèces ligneuses mais pas sur celle de l’herbacée. La compétition interspécifique a généralement augmenté la survie de C. albidus et B. retusum comparé à la compétition intraspécifique. A l’inverse, la compétition interspécifique a diminué la survie de Q. coccifera. De la même manière, les traits morphologiques racinaires ont été plus affectés par l’identité des espèces voisines que par le traitement de sécheresse. Les profils métaboliques des communautés microbiennes (CLPP) de sol associé aux racines n’ont pas été affectés par les traitements de sécheresse ni par l’identité des espèces végétales. Cependant, avec l’augmentation de la profondeur du sol, les CLPP ont augmentés mais avec une utilisation de ressources moins diversifiées. Ces résultats suggèrent que la composition d’espèces végétales de la garrigue méditerranéenne étudiée a un effet plus important sur la croissance, la variabilité intraspécifique des traits racinaires et la survie que les sécheresses sévères répétées.Dans le contexte d’un projet collaboratif (CLIMED), j’ai utilisé un gradient naturel de diversité d’espèces d’arbustes d’un écosystème de garrigue méditerranéenne ayant reçu un traitement d’exclusion de pluie partielle (-12% de précipitation). Cette expérience m’a permis d’étudier les réponses des profils métaboliques des communautés microbiennes du sol CLPP à une diminution des précipitations ainsi qu’à un changement de diversité des litières végétales décomposant au sol comme ressource clé pour les microorganismes hétérotrophiques du sol, pendant deux ans. Alors que l’exclusion de pluie n’a eu qu’un impact mineur sur la diversité des substrats métabolisés par les communautés microbiennes, la richesse spécifique de la litière a favorisé l’activité microbienne du sol en augmentant la diversité catabolique de la communauté microbienne du sol. Ces résultats suggèrent que les effets indirects du changement climatique sur la composition et la richesse des espèces végétales pourraient avoir des conséquences plus importantes pour le fonctionnement microbien du sol que la réduction des précipitations prévue dans l’écosystème de garrigue méditerranéenne étudié.Mes deux études, de terrain et en rhizotron, ont clairement montrées que l’identité et la diversité des espèces végétales peuvent être plus importantes pour le fonctionnement de ces garrigues méditerranéennes qu’une augmentation des sécheresses. Je conclus que les changements de composition et de diversité d’espèces végétales induits par le changement climatique peuvent avoir des conséquences plus importantes pour le fonctionnement des garrigues méditerranéennes que les effets directs d’une modification des précipitations / Longer drought periods and/or overall less precipitation are thought to be major consequences of ongoing climate change in the Mediterranean region. These changes in the water regime will likely affect community composition, biodiversity and ecosystem processes, but very little is known about how biodiversity and changes in precipitation interactively affect ecosystem functioning. In my PhD thesis, I aimed to quantify the role of plant diversity in the response of Mediterranean shrubland ecosystem to a decrease in water availability, with a particular interest in belowground processes, such as soil microbial community functioning and functional responses in plant roots.I used a rhizotron approach under partially controlled conditions to study plant growth responses to repetitive severe droughts, with a particular focus on root growth. Two individuals of the same species or in all possible combinations of the three dominating species at our field site (Quercus coccifera, Cistus albidus, Brachypodium retusum) were grown together in a rhizotron. Repetitive severe droughts had a negative effect on survival of the two woody species (Q. coccifera, C. albidus), but not of the grass B. retusum. Interspecific competition generally increased survival of C. albidus and B. retusum compared to monospecific competition. Conversely, interspecific competition decreased the survival of Q. coccifera. Likewise, I found that root morphological traits were mostly affected by the neighbor species identity rather than by severe drought. The community level physiological profiles (CLPPs) of root associated soil microbial communities did not differ between drought treatments and were also not affected by plant species identity. However, CLPPs changed towards more total microbial activities but less diverse resource use at increasing soil depth. Collectively these results suggest that plant species composition of the studied Mediterranean shrubland has a stronger effect on growth, intraspecific variability in root traits and survival than repetitive severe droughts.In the context of a larger collaborative project (CLIMED), I used a natural gradient of shrub species diversity in a Mediterranean shrubland ecosystem (garrigue) to which a permanent partial rain exclusion treatment (12% less precipitation) was added. This field experiment allowed me to study the responses of soil microbial community level physiological profiles (CLPPs) to reduced precipitation and to a change plant-produced leaf litter material decomposing on the ground as a key resource for heterotrophic soil microorganisms over two years. While rain exclusion had only a minor impact on the diversity of substrates metabolized by the microbial communities, litter species richness promoted global soil microbial activity by increased catabolic diversity of the soil microbial community. These results suggest that indirect climate change effects on plant species composition and richness might have more important consequences for soil microbial functioning than reduced precipitation in the studied Mediterranean shrubland ecosystem.Both, the field study of soil microbial functioning and the rhizotron study of plant growth and survival clearly showed that plant species identity and diversity may be more important for the functioning of these Mediterranean shrublands than increased drought. I conclude that climate change induced shifts in plant species composition and diversity may have more important consequences for the functioning of Mediterranean shrublands than the direct effects of altered precipitation.