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A poluição plástica gerada por microplásticos é apontada como o novo inimigo a ser combatido. Desta forma, é de fundamental importância compreender parâmetros como: classificação, obtenção, distribuição na natureza, características físico-químicas e morfológicas desse material. Indícios apontam que a foto-oxidegradação é um dos principais mecanismos de geração de microplásticos no meio ambiente, além de definir a sua adsorção de poluentes. Estudos sobre os mecanismos de adsorção tem sido auxiliados com a utilização de modelos matemáticos cinéticos e termodinâmicos como: pseudo primeira e segunda ordem, difusão intraparticulas e em filme, isoterma de Langmuir e de Freundlich, que são utilizados para caracterizar os processos e mecanismos da adsorção. Além da caracterização teórica, as físicas são necessárias para definir marcadores e quantificar a presença desses materiais. Para essas caracterizações físicas são utilizados equipamentos, como: Espectroscopia no Infravermelho com Transformada de Fourier (FTIR), Espectroscopia no UV/Visível (UV-Vis), Microscopia Eletrônica de Varredura (SEM) e a espectroscopia de Ressonância Magnética Nuclear (NMR).

Bamboo (Dendrocalamus giganteus) is a functionally graded material with well-organized hierarchical structures. Its micrometer-sized vascular bundles and parenchymatic living cells allow an efficient upward flow of water and nutrients, endowing the organism with remarkably fast growth. As demonstrated recently, the hollow microstructure channels can be explored as a natural template for microfluidics applications in chemical synthesis, analytical detection, solar steam generation, and electrochemical devices. Thus, the knowledge of the kinetics of the imbibition and spatial distribution of fluid through the microcavities of the bamboo vegetal tissue became of interest. Here, we employed a combination of X-ray microtomography (µCT) and proton time-domain NMR (TD-NMR) to identify, measure, and investigate empty volumes embedded in the bamboo’s tissue as experienced by different organic and inorganic fluids, namely dimethyl sulfoxide (DMSO) and distilled water (H2O). Results have shown that the extensive communication between the voids (parenchymal cells and vascular channels) does not prevent the individuation of fluid reservoirs with different behaviors, as evidenced by the H2O desorption profile. Bamboo parenchyma was the tissue that retained more residual H2O after desorption. The difference in wettability of bamboo tissues by DMSO and H2O was detected. Graphical abstract

Bioinformatics pipelines for calling star alleles (haplotypes) in cytochrome P450 (CYP) genes are important for the implementation of precision medicine. Genotyping CYP genes using high throughput sequencing data is complicated, e.g., by being highly polymorphic, not to mention the structural variations especially in CYP2D6, CYP2A6, and CYP2B6. Genome graph-based variant detection approaches have been shown to be reliable for genotyping HLA alleles. However, their application to enhancing star allele calling in CYP genes has not been extensively explored. We present StellarPGx, a Nextflow pipeline for accurately genotyping CYP genes by combining genome graph-based variant detection, read coverage information from the original reference-based alignments, and combinatorial diplotype assignments. The implementation of StellarPGx using Nextflow facilitates its portability, reproducibility, and scalability on various user platforms. StellarPGx is currently able to genotype 12 important pharmacogenes belonging to the CYP1, 2, and 3 families. For purposes of validation, we use CYP2D6 as a model gene owing to its high degree of polymorphisms (over 130 star alleles defined to date, including complex structural variants) and clinical importance. We applied StellarPGx and three existing callers to 109 whole genome sequenced samples for which the Genetic Testing Reference Material Coordination Program (GeT-RM) has recently provided consensus truth CYP2D6 diplotypes. StellarPGx had the highest CYP2D6 diplotype concordance (99%) with GeT-RM compared with Cyrius (98%), Aldy (82%), and Stargazer (84%). This exemplifies the high accuracy of StellarPGx and highlights its importance for both research and clinical pharmacogenomics applications. The StellarPGx pipeline is open-source and available from https://github.com/SBIMB/StellarPGx.

This work deals with the thermodynamic selective localization of hydroxyapatite nanoparticles (Hap) and its effects on crystallization and molecular dynamics in immiscible polyester blend films based on poly(3-hydroxybutyrate) (PHB, 90 wt%) and polycaprolactone (PCL, 10 wt%). Polymer blend composite films were obtained through solution casting method and characterized by contact angle (surface energy measurements), ultraviolet–visible spectroscopy (UV–Vis), elemental mapping, X-ray diffraction (WAXD), differential scanning calorimetry (DSC), polarized optical microscopy (POM) and time domain nuclear magnetic resonance (TD-NMR) techniques. It was found that hydroxyapatite (Hap) is selectively localized in the PHB phase and consequently, nanoparticles strongly influenced the PHB crystallization behavior. DSC and POM results indicated that hydroxyapatite nanoparticles acted as a nucleating agent. However, no significant changes in crystallinity degree were observed by WAXD. Fractionated crystallization behavior was observed for PCL droplets and the increase in the Hap concentration promoted heterogeneous nucleation on the droplets surface due to the nanoparticles close to the interface. Molecular dynamics studies by TD-NMR suggested a disordered Hap nanoparticles distribution inside the polymer matrix, leading to slower dynamics in the semirigid fraction of the sample´s magnetization, typically attributed to restricted polymeric chains close to the particle’s surface.

More than two decades ago, a recessive syndromic phenotype affecting kidneys, eyes, and ears, was first described in the endogamous Afrikaner population of South Africa. Using whole-exome sequencing of DNA from two affected siblings (and their carrier parents), we identified the novel RRM2B c.786G>T variant as a plausible disease-causing mutation. The RRM2B gene is involved in mitochondrial integrity, and the observed change was not previously reported in any genomic database. The subsequent screening revealed the variant in two newly presenting unrelated patients, as well as two patients in our registry with rod-cone dystrophy, hearing loss, and Fanconi-type renal disease. All patients with the c.786G>T variant share an identical 1.5 Mb haplotype around this gene, suggesting a founder effect in the Afrikaner population. We present ultrastructural evidence of mitochondrial impairment in one patient, to support our thesis that this RRM2B variant is associated with the renal, ophthalmological, and auditory phenotype.

Silica-based (SiO2) poly(3-hydroxybutyrate) (PHB) nanocomposites were obtained via an in situ sol–gel route in three distinct particle concentrations (1, 5, and 7.5% by weight of PHB). The polymer hybrids formed were analyzed via wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), Fourier transform infrared (FTIR) spectroscopy, and time-domain nuclear magnetic resonance relaxometry (TD-NMR). The SiO2 inorganic structure displayed surface fractal features at low concentration (1 wt%) and denser agglomerates at higher concentrations (5 and 7.5 wt%). FTIR and SAXS results confirmed the formation of the inorganic matrix amid the polymer chains with different levels of distribution and organization. WAXD and TD-NMR results suggested the SiO2 influence on the PHB crystallinity degree, which was reflected on the polymer’s molecular dynamics with a nonlinear dependence of particles concentration in the PHB matrix.

The 11th Congress of the African Society of Human Genetics (AfSHG) was held from September 16, 2018 to September 21, 2018, in conjunction with the 12th Human Heredity and Health in Africa (H3Africa) Consortium meeting in Kigali, Rwanda. The event was organized by the AfSHG in partnership with the Rwanda Society of Human Genetics and the University of Rwanda. A 2-day workshop on the application of next-generation sequencing technologies for analyzing monogenic disease in African populations was organized as part of the conference (September 22, 2018-September 23, 2018, Kigali, Rwanda). The theme of the conference was "Building skills and resources for genomics, epigenetics and bioinformatics research for Africa."The conference served as a platform to bring together members from country-specific Societies of Human Genetics, including Rwanda, Cameroon, Democratic Republic of Congo, Egypt, Mali, Senegal, and South Africa, and included 435 delegates from 38 countries, including 29 African countries that attended the conference. A major topic of discussion was how to bridge the gap between the emerging knowledge on genomics and Omics in African populations. The importance of understanding the role of genetic variation in disease causation and susceptibility among Africans was a constant theme during the meeting, as was the need to develop research infrastructure and resources to enhance healthcare systems, so that they are not left behind in the genomic revolution. It was concluded that there is a need to inspire more African scientists to train and work as investigators, clinicians, and genetic counselors in the field of human genetics in Africa. Local investments, and South-South and South-North collaboration were identified as the key drivers for the successful implementation of research and development on the continent., SCOPUS: ar.j, info:eu-repo/semantics/published

Effective interventions and treatments for complex diseases have been implemented globally, however, coverage in Africa has been comparatively lower due to lack of capacity, clinical applicability and knowledge on the genetic contribution to disease and treatment. Currently, there is a scarcity of genetic data on African populations, which have enormous genetic diversity. Pharmacogenomics studies have the potential to revolutionise treatment of diseases, therefore, African populations are likely to benefit from these approaches to identify likely responders, reduce adverse side effects and optimise drug dosing. This review discusses clinical pharmacogenetics studies conducted in African populations, focusing on studies that examined drug response in complex diseases relevant to healthcare. Several pharmacogenetics associations have emerged from African studies, as have gaps in knowledge.

O presente estudo propoe a utilizacao de polimeros alternativos para a obtencao de alcool em gel 70% como ferramenta de higiene no combate ao Covid-19. Alem da carboximetilcelulose, foram utilizados polimeros comerciais, descritos como derivados da celulose, Carbomex e Maxcarb, os quais apresentam propriedades gelificantes em potencial em diversas areas. As formulacoes foram obtidas utilizando diferentes concentracoes dos agentes gelificantes com agua, glicerina e etanol. Os materiais iniciais, bem como as formulacoes obtidas, foram caracterizados por diferentes tecnicas, incluindo Difracao de Raios X, Relaxometria, Analise termogravimetrica. Os resultados das analises de Raios X indicaram uma maior cristalinidade do material obtido com Maxcarb e Carbomex quando comparados a Carboximetilcelulose. A analise termogravimetrica dos materiais indicou que o Maxcarb possui o maior valor de temperatura de degradacao. Com as analises de relaxometria foi possivel obter os tempos de relaxacao dos materiais em solucao e nos estado solido. A Carboximetilcelulose apresentou menor valor de relaxacao spin-rede quando comparado ao Maxcarb e Carbomex que apresentaram menores valores.

We propose the small-angle flip-flop (SAFF) pulse sequence as an alternative procedure for the rapid measurement of the 1 H spin-lattice relaxation time in the laboratory frame (T1 ) of solid and liquid substances, in a time-domain NMR experiment. Based on the original flip-flop pulse sequence, this technique allows the fast estimation of T1 values of samples that require minutes to hours of acquisition time if traditional pulse sequences are employed. We have applied SAFF to different substances, with T1 ranging from microseconds up to seconds, including natural clays, polymers, and organic and inorganic solvents. We also demonstrate the potential of the pulse sequence in the real-time monitoring of dynamic processes, such as the conformational changes of polymeric materials during heating. The results we obtained with SAFF are comparable with those acquired with the inversion-recovery pulse sequence, with the addition of several benefits. This pulse sequence obeys steady-state and magnetization-conserving principles, making it possible to dismiss the need for relaxation delay times of the order of 5T1 . SAFF has shown high sensitivity in the resolution of individual components of T1 in multiexponential systems and can be easily integrated to well-established pulse sequences, such as Magic Sandwich Echo and Carr-Purcell-Meiboom-Gill, for the single-shot determination of T1 and T2 or T2* .

Pharmacogenomics aims to reveal variants associated with drug response phenotypes. Genes whose roles involve the absorption, distribution, metabolism, and excretion of drugs, are highly polymorphic between populations. High coverage whole genome sequencing showed that a large proportion of the variants for these genes are rare in African populations. This study investigated the impact of such variants on protein structure to assess their functional importance. We used genetic data of CYP3A5 from 458 individuals from sub-Saharan Africa to conduct a structural bioinformatics analysis. Five missense variants were modeled and microsecond scale molecular dynamics simulations were conducted for each, as well as for the CYP3A5 wildtype and the Y53C variant, which has a known deleterious impact on enzyme activity. The binding of ritonavir and artemether to CYP3A5 variant structures was also evaluated. Our results showed different conformational characteristics between all the variants. No significant structural changes were noticed. However, the genetic variability seemed to act on the plasticity of the protein. The impact on drug binding might be drug dependant. We concluded that rare variants hold relevance in determining the pharmacogenomics properties of populations. This could have a significant impact on precision medicine applications in sub-Saharan Africa.

Genetic variation in genes encoding cytochrome P450 enzymes has important clinical implications for drug metabolism. Bioinformatics algorithms for genotyping these highly polymorphic genes using high-throughput sequence data and automating phenotype prediction have recently been developed. The CYP2D6 gene is often used as a model during the validation of these algorithms due to its clinical importance, high polymorphism, and structural variations. However, the validation process is often limited to common star alleles due to scarcity of reference datasets. In addition, there has been no comprehensive benchmark of these algorithms to date. We performed a systematic comparison of three star allele calling algorithms using 4618 simulations as well as 75 whole-genome sequence samples from the GeT-RM project. Overall, we found that Aldy and Astrolabe are better suited to call both common and rare diplotypes compared to Stargazer, which is affected by population structure. Aldy was the best performing algorithm in calling CYP2D6 structural variants followed by Stargazer, whereas Astrolabe had limitations especially in calling hybrid rearrangements. We found that ensemble genotyping, characterised by taking a consensus of genotypes called by all three algorithms, has higher haplotype concordance but it is prone to ambiguities whenever complete discrepancies between the tools arise. Further, we evaluated the effects of sequencing coverage and indel misalignment on genotyping accuracy. Our account of the strengths and limitations of these algorithms is extremely important to clinicians and researchers in the pharmacogenomics and precision medicine communities looking to haplotype CYP2D6 and other pharmacogenes using high-throughput sequencing data.

Investigating variation in genes involved in theabsorption, distribution, metabolism, andexcretion(ADME) of drugs are key to characterising pharmacogenomic (PGx) relationships. ADME gene variation is relatively well characterised in European and Asian populations, but African populations are under-studied – which has implications for safe and effective drug use in Africa.The genetic diversity of ADME genes across sub-Saharan African populations is large. The Southern African population cluster is most distinct from that of far West Africa. PGx strategies based on European variants will be of limited use in African populations.Although established variants are important, PGx must take into account the full range of African variation. This work urges further characterisation of variants in African populations includingin vitroandin silicostudies, and to consider the unique African ADME landscape when developing precision medicine guidelines and tools for African populations.Author summaryThe ADME genes are a group of genes that play a key role in absorption, distribution, metabolism and excretion of drugs. Variations in these genes can have a significant impact on drug safety and efficacy. Africa has a high level of genetic variation and is under-studied in drug development, which makes study of variations in these genes in African populations very important. Using a new data set of 458 high-coverage genomes from across Africa, we characterise the extent and impact of variation in the ADME genes, looking at both single nucleotide and copy number variations. We identified 343,368 variants, including 40,692 novel variants, and 930 coding variants which are predicted to have high impact on function. Our discovery curves indicate that there will be considerable value in sequencing more African genomes. Moreover, relatively few of these novel variants are captured on common genotyping arrays. We show that there is considerable diversity within Africa in some important genes, and this will have significant consequences for the emerging field of precision medicine in Africa.

Chloroquine/hydroxychloroquine have been proposed as potential treatments for COVID-19. These drugs have warning labels for use in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Analysis of whole genome sequence data of 458 individuals from sub-Saharan Africa showed significant G6PD variation across the continent. We identified nine variants, of which four are potentially deleterious to G6PD function, and one (rs1050828) that is known to cause G6PD deficiency. We supplemented data for the rs1050828 variant with genotype array data from over 11,000 Africans. Although this variant is common in Africans overall, large allele frequency differences exist between sub-populations. African sub-populations in the same country can show significant differences in allele frequency (e.g. 16.0% in Tsonga vs 0.8% in Xhosa, both in South Africa, p = 2.4 × 10−3). The high prevalence of variants in the G6PD gene found in this analysis suggests that it may be a significant interaction factor in clinical trials of chloroquine and hydroxychloroquine for treatment of COVID-19 in Africans.

Chloroquine/hydroxychloroquine have been proposed as potential treatments for COVID-19. These drugs have warning labels for use in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Analysis of whole-genome sequence data of 458 individuals from sub-Saharan Africa showed significant G6PD variation across the continent. We identified nine variants, of which four are potentially deleterious to G6PD function, and one (rs1050828) that is known to cause G6PD deficiency. We supplemented data for the rs1050828 variant with genotype array data from over 11,000 Africans. Although this variant is common in Africans overall, large allele frequency differences exist between sub-populations. African sub-populations in the same country can show significant differences in allele frequency (e.g. 16.0% in Tsonga vs 0.8% in Xhosa, both in South Africa, p = 2.4 × 10−3). The high prevalence of variants in the G6PD gene found in this analysis suggests that it may be a significant interaction factor in clinical trials of chloroquine and hydrochloroquine for treatment of COVID-19 in Africans.

The spread of COVID-19 caused by the SARS-CoV-2 outbreak has been growing since its first identification in December 2019. The publishing of the first SARS-CoV-2 genome made a valuable source of data to study the details about its phylogeny, evolution, and interaction with the host. Protein-protein binding assays have confirmed that Angiotensin-converting enzyme 2 (ACE2) is more likely to be the cell receptor through which the virus invades the host cell. In the present work, we provide an insight into the interaction of the viral spike Receptor Binding Domain (RBD) from different coronavirus isolates with host ACE2 protein. By calculating the binding energy score between RBD and ACE2, we highlighted the putative jump in the affinity from a progenitor form of SARS-CoV-2 to the current virus responsible for COVID-19 outbreak. Our result was consistent with previously reported phylogenetic analysis and corroborates the opinion that the interface segment of the spike protein RBD might be acquired by SARS-CoV-2 via a complex evolutionary process rather than a progressive accumulation of mutations. We also highlighted the relevance of Q493 and P499 amino acid residues of SARS-CoV-2 RBD for binding to human ACE2 and maintaining the stability of the interface. Moreover, we show from the structural analysis that it is unlikely for the interface residues to be the result of genetic engineering. Finally, we studied the impact of eight different variants located at the interaction surface of ACE2, on the complex formation with SARS-CoV-2 RBD. We found that none of them is likely to disrupt the interaction with the viral RBD of SARS-CoV-2., Highlights • We noticed a large difference in the binding energy of RBD from the spike protein of SARS-CoV-2 with ACE2, compared to the closest isolates to the proposed progenitor forms. • Currently, available sequence data do not explain the transition from low-affinity RBD forms to high-affinity RBD that are capable to infect the Humans. • We suggest that residues N493Q and not N501T as was reported previously is responsible for a higher affinity toward ACE2 when we compare SARS-CoV-2 to SARS-CoV. • The mutation T499P is responsible for stabilizing the interface of RBD interacting with ACE2 when we compare SARS-CoV-2 to SARS-CoV. • It is unlikely that the interface of RBD from SARS-CoV-2 is a result of human intervention aiming to increase the affinity toward ACE2. • The role of receptors other than ACE2 is shown, and these may have a more critical function in crossing the species barrier. • Variants that corresponding to residues on the ACE2 interface are unlikely to be associated with resistance or sensibility forms compared to the reference allele.

Synthesis reactions of polyacrylamide based hydrogels were automatically monitored in situ by time-domain nuclear magnetic resonance, through a steady-state pulse sequence. Four hydrogel formulations with different amounts of monomer and crosslinking agent were tested and the proposed method demonstrated sensitivity to each formulation without the need for a priori calibration of the spectrometer, even when the hydrogels exhibited substantially different structural characteristics. The results obtained by the proposed method were compared for validation with those generated by traditional reaction monitoring methods, such as UV–Vis spectroscopy, and exhibited similar results, suggesting that time-domain nuclear magnetic constitutes an interesting alternative for the monitoring of solution crosslinking reactions.

Blends of two different biodegradable polyesters, poly(3-hydroxybutyrate) (PHB) and low molecular weight polycaprolactone (PCL), were obtained through solution casting and their miscibility and crystallinity were studied. The materials were characterized by wide angle X-ray diffraction, differential scanning calorimetry (DSC) and time-domain nuclear magnetic resonance (TD-NMR). Blends with PCL concentrations higher than 60% (w/w) were not obtained due the inability of low molecular weight PCL to form films by this method. The DSC technique revealed that the films were not miscible since there were no changes in the PHB glass transition temperature (T g ) after the PCL addition. However, the TD-NMR technique showed some partial miscibility, observed in the blend containing 10% (w/w) PCL, revealing domains around 30 nm, where the spin diffusion process was extremely close to that observed in the pure polymers. Other than that, the transversal relaxation showed that the partial miscibility of this composition occurs predominantly in the chain segments located in the interphase intercalation of the rigid regions, reducing the systems' crystallinity. These results are in accordance with the findings obtained through the WAXD analysis.

Poly(vinyl alcohol) (PVA)-based chemically cross-linked xerogels, both neat and loaded with nanoparticulate hydrophilic silica (SiO2), were obtained and characterized mainly through time domain NMR experiments (TD-NMR). Fourier-transform infrared (FT-IR) and wide angle X-ray diffraction (WAXD) analyses were employed as secondary methods. TD-NMR, through the interpretation of the spin-lattice relaxation constant values and related information, showed both cross-linking and nanoparticle influences on PVA matrix. SiO2 does not interact chemically with the PVA chains, but has effect on its molecular mobility, as investigated via TD-NMR. Apparent energy of activation, spin-lattice time constant and size of spin domains in the sample have almost linear dependence with the degree of cross-linking of the PVA and are affected by the addition of SiO2. These three parameters were derived from a single set of TD-NMR experiments, which demonstrates the versatility of the technique for characterization of inorganic-organic hybrid xerogels, an important class of materials.

Plants harbor bacteria which can provide them with benefits such as growth promotion, enhancement of nutrient uptake, defense against pathogens and predators, and improvement of tolerance to abiotic factors such as drought. The development of biotechnological applications using these bacteria has been the focus of research and interest from the scientific community and agricultural sector. While crops have received significant attention, plant species growing in natural environments were neglected and should also be explored. This is particularly important in the paradigm of climate change and its threat to plant productivity, especially due to drought and desertification. This thesis aimed to study the diversity of bacteria living in legume root nodules from wild areas in continental Portugal., to understand if the site of origin and climate conditions influence bacterial osmotolerance, and to evaluate the plant growth promotion abilities of bacterial strains towards the non-legume plant model Arabidopsis thaliana. The bacterial strains isolated from different wild legume species were characterized by BOX-PCR and partial 16S rRNA gene sequencing. These strains, which belonged mainly to the genera Flavobacterium and Pseudomonas, were used to evaluate their plant growth promoting abilities (production of siderophores, indol acetic acid, emission of volatiles) and their tolerance to osmotic stress. A representative set of strains from the different genera was used to study the mechanisms behind the response to osmotic stress (osmolytes and antioxidant mechanisms). It was possible to suggest intracellular alginate as a new mechanism of bacterial osmotolerance. In this thesis, a particular focus has been given to the mechanism of plant growth promotion by bacterial volatiles. The volatile metabolites released by two bacterial strains (Flavobacterium sp. D9 and Rhizobium sp. E20-8) were captured using solid-phase microextraction and analyzed by gas chromatography – mass spectrometry and two-dimensional gas chromatography – mass spectrometry. The effects of bacterial volatiles emission on several physiological and biochemical endpoints of A. thaliana were also evaluated, in control and osmotic stress (drought). Globally, the results of this thesis evidenced the potential of wild legume plant species as sources of bacteria promoting the growth and tolerance to drought of plant species, including legumes and non-legumes, which should be the used as an agricultural practice to increase crop production, particularly in drought conditions. As plantas são habitadas por bactérias que lhes podem trazer benefícios, como por exemplo a promoção do seu crescimento, a melhoria da aquisição de nutrientes, defesa contra agentes patogénicos e predadores, e melhoria da tolerância a fatores abióticos como por exemplo a seca. O desenvolvimento de aplicações biotecnológicas utilizando estas bactérias desde há muito que interessa a comunidade científica e o setor da agricultura. Enquanto que as espécies de plantas cultivadas têm recebido bastante atenção, as espécies de plantas a crescer em ambientes naturais têm sido negligenciadas e também devem ser exploradas nesse sentido. Este interesse é redobrado num contexto de ameaça à produtividade agrícola por parte das alterações climáticas, e em particular a seca e associada desertificação. Esta tese teve como objetivos explorar a diversidade de bactérias existentes nos nódulos das raízes de plantas leguminosas a crescer em ambiente selvagem em Portugal continental, perceber se as condições edafoclimáticas do local de origem afetam a osmotolerância das bactérias, e avaliar as capacidades de promoção de crescimento de uma planta modelo, não leguminosa, a Arabidopsis thaliana. As estirpes bacterianas isoladas a partir de várias espécies de plantas leguminosas a crescer em Portugal continental foram caracterizadas por BOX-PCR fingerprinting e amplificação parcial e sequenciação do gene que codifica para o 16S rRNA. Estas estirpes, predominantemente dos géneros Flavobacterium e Pseudomonas, foram utilizadas para avaliar a sua capacidade de evidenciar capacidades promotoras do crescimento das plantas (produção de sideróforos, ácido indol acético, emissão de compostos voláteis) e a sua tolerância ao stress osmótico. Um conjunto representativo de estirpes de diferentes géneros foi utilizado para estudar os mecanismos de resposta ao stress osmótico (osmólitos e mecanismos antioxidantes), tendo sido possível apontar o alginato intracelular como um possível novo mecanismo de osmotolerância bacteriana. Nesta tese, um enfoque particular foi dado ao mecanismo de promoção de crescimento de plantas através da emissão de metabolitos voláteis pelas bactérias. Os metabolitos voláteis emitidos por duas estipes bacterianas (Flavobacterium sp. D9 e Rhizobium sp. E20-8), promotoras do crescimento de A. thaliana, foram captados por microextração em fase sólida e analisados por cromatográfica gasosa e cromatografia gasosa bidimensional e espectrometria de massa. Foram também avaliados os efeitos da emissão de voláteis em diversos parâmetros fisiológicos e bioquímicos das plantas, em condições controlo e condições de stress osmótico (seca). Globalmente, os resultados desta tese evidenciam o potencial das espécies de leguminosas selvagens como fontes de bactérias que promovem o crescimento e tolerância à seca de espécies de plantas, incluindo leguminosas e não leguminosas, e que devem ser usadas como prática agrícola para aumentar a produtividade, particularmente em condições de seca. Programa Doutoral em Biologia e Ecologia das Alterações Globais