Os produtos naturais desempenham fundamental importância na descoberta de novos fármacos. Muitos destes fármacos originaram-se de produtos naturais microbianos o que demonstra uma extrema eficiência na habilidade dos micro-organismos de sintetizar substâncias químicas com elevado potencial biológico. Sabe-se que os insetos sociais estão sujeitos a condições climáticas e populacionais que aumentam sua susceptibilidade a parasitas. Assim, estes insetos desenvolveram um mecanismo de defesa evolutivo que consiste na associação simbiótica a bactérias capazes de biossintetizar produtos antimicrobianos contra os patógenos. Dispondo dessas informações, o presente trabalho contribuiu com o estudo dos produtos naturais biossintetizados pela bactéria Paenibacillus polymyxa ALLI-03-01, provável simbionte da espécie de abelha sem ferrão Melipona scutellaris. Os micro-organismos foram isolados de colônias mantidas no Departamento de Biologia da FFCLRP-USP. Todas as linhagens foram testadas contra dois fungos entomopatogênicos - Beauveria bassiana e Metarhizium anisopliae; os que apresentaram atividade antifúngica tiveram seus extratos em acetato de etila e metanol preparados e foram avaliados em ensaios antiparasitários contra Trypanosoma cruzi e Leishmania donovani. A bactéria ALLI-03-01, isolada do alimento larval, foi escolhida para os estudos químicos, pois apresentou satisfatória atividade antifúngica e proeminente atividade antiparasitária. Este micro-organismo foi identificado pelo sequenciamento do gene 16S rRNA como sendo a bactéria Paenibacillus polymyxa, conhecida pela alta capacidade de produção de metabólitos secundários. Para conhecer seu metabolismo, esta bactéria foi cultivada em meio ISP-2 ágar e líquido e do extrato em acetato de etila do cultivo fermentativo de P. polymyxa ALLI-03-01 foi isolado o ácido L-3-fenil lático. As atividades antifúngicas dos padrões comerciais dos ácidos D-(+)- e L-(-)- 3-fenil lático foram testadas frente ao fungo entomopatogênico B. bassiana e apenas o enantiômero L apresentou atividade antifúngica. Do extrato em metanol do cultivo em meio sólido do mesmo micro-organismo foram identificados em mistura, principalmente por MALDI-TOF MS/MS, nove diferentes ciclolipodepsipeptídeos, da classe das Fusaricidinas. As fusaricidinas são conhecidas por apresentarem alta atividade anti-microbiana, que foi comprovada quando duas frações compostas por diferentes fusaricidinas foram testadas frente ao fungo entomopatogênico Metarhizium anisopliae e contra a bactéria patogênica Paenibacillus larvae. As frações apresentaram resultados satisfatórios de inibição contra ambos os patógenos, dessa maneira as fusaricidinas e a produção seletiva do ácido L-3-fenil lático por esta bactéria podem ser vias de proteção da colônia, evitando que patógenos destruam-na e permitindo o desenvolvimento sadio de larvas. Sendo assim, este trabalho relata pela primeira vez a possível relação simbiótica existente entre o micro-organismo Paenibacillus polymyxa ALLI-03-01 e a colônia de abelhas Melipona scutellaris, bem como a produção por este micro-organismo de compostos com alta atividade antimicrobiana que podem exercer o controle de parasitas dentro da colônia, estabelecendo assim, uma possível relação ecológica entre o micro-organismo destacado e as abelhas Melipona scutellaris. / Natural products play an important role in drug discovery. Several drugs have been discovered or developed from microbial natural products hits and leads showing a great efficiency of microorganisms to synthesize compounds with high biological potential. It is known that social insects are subjected to climate and population conditions that increase their susceptibility to parasites. Therefore, these insects have developed an evolutionary defense mechanism consisting in symbiotic association with bacteria capable of biosynthesize antimicrobial products against pathogens. In this context, this study contributed to the knowledge of natural products biosynthesized by the bacterium Paenibacillus polymyxa ALLI-03-01, a probable symbiont of the stingless bee Melipona scutellaris. Microorganisms were isolated from colonies maintained at the Department of Biology of FFCLRP-USP. All strains were tested against two entomopathogenic fungi - Beauveria bassiana and Metarhizium anisopliae; strains that showed antifungal activity had their ethyl acetate and methanol extracts prepared and evaluated against the parasites Trypanosoma cruzi and Leishmania donovani. The bacterium ALLI-03-01, isolated from larval food, was selected for chemical studies, due to its satisfactory antifungal activity and outstanding antiparasitic activity. This microorganism was identified by gene 16S rRNA sequencing as Paenibacillus polymyxa, a bacterium recognized for its ability of biosynthesize secondary metabolities. This bacterium was cultivated in ISP-2 agar and liquid medium and from the ethyl acetate extract of P. polymyxa ALLI-03-01 cultivated in liquid medium L-3-phenyllactic acid was isolated. The antifungal activity of comercial standards of D-(+)- and L-(-)-phenyllactic acid were tested against entomopathogenic fungus B. bassiana and only the L enantiomer presented antifungal activity. Nine cyclo lipodepsipeptides known as fusaricidins were identified in mixture using MALDI-TOF-MS/MS from the methanol extract of ALLI-03-01. The fusaricidins are recognized for their high antimicrobial activity, which was confirmed when two fractions composed by different fusaricidins were tested against the entomopathogenic fungus Metarhizium anisopliae and the pathogenic bacterium Paenibacillus larvae. The fractions showed satisfactory inhibition against both pathogens. Therefore, fusaricidins and selective production of L-3-phenyllactic acid by the bacterium may be colony protection resources, preventing the action of pathogens and allowing healthy larvae development. Therefore, this study reports for the first time a possible symbiotic relationship between Paenibacillus polymyxa ALLI-03-01 and the colony of M. scutellaris bees, as well as production of compounds with high antimicrobial activity by this microorganism that might act as parasite control agents within the colony, establishing a possible ecological relationship between the bacterium and M. scutellaris bees.

Photocatalysis is an advanced oxidation process, which has shown to possess an enhanced capability to remove a wide range of contaminants. It involves the use of a semiconductor photocatalyst and a photon source. Photocatalysis has several advantages such as mild reaction conditions like ambient temperature and pressure, good control over the reaction and faster reaction kinetics. Semiconductor photocatalysts such as TiO2, ZnO, Fe2O3, CdS, ZnS, etc. absorbs light of energy greater than or equal to its band gap and the electron in the valence band gets excited to conduction band leaving behind the hole in valence band. These charge carrier pair results in the formation of various reactive oxygen species such as hydroxyl and superoxide radicals which results in the degradation of chemical contaminants and inactivation of microorganisms. TiO2 is the most widely used catalyst in photocatalytic studies because of its high photocatalytic activity, non-toxicity and wide availability. Anatase phase TiO2 has been reported to possess higher photocatalytic activity than the rutile phase. Although there are several methods to synthesize TiO2, solution combustion synthesis is a single step process to produce pure anatase phase TiO2. The catalyst produced by this method has been shown to be superior to the commercially available Degussa P-25 catalyst for the degradation of various chemical contaminants. The present investigation focuses on the use of combustion synthesized catalyst for the inactivation of microorganisms. The photocatalytic activity was compared with commercial Degussa P-25 catalyst. The various aspects of photocatalytic inactivation reactions studied in this dissertation are: i) photocatalytic inactivation of microorganisms in presence of UV light, ii) effect of various parameters on the inactivation, iii) photocatalytic inactivation in presence of visible light, iv) use of immobilized catalyst for the photocatalytic inactivation, v) understanding of mechanism and kinetics of inactivation. Combustion synthesized TiO2 (CS-TiO2), combustion synthesized 1% Ag substituted TiO2 (Ag/TiO2 (Sub)) and 1% Ag impregnated CS-TiO2 (Ag/TiO2 (Imp)) were used as photocatalysts. The catalysts were characterized by powder XRD, TEM, BET surface area, UV-Vis spectroscopy, TGA and photoluminescence spectroscopy. The photocatalytic inactivation experiments were carried out using E. coli (K-12 MG 1655), a bacterial strain and P. pastoris (X-33), a yeast strain, as model microorganisms. The results demonstrate higher photocatalytic activity of all the combustion synthesized catalysts than commercial Degussa P-25 catalyst. The optimum catalyst concentration was 0.25 g/L and the maximum inactivation was observed in the presence of Ag/TiO2 (Imp) catalyst. Rapid and complete inactivation of the microorganisms was observed at lower initial cell concentrations. A reduced photocatalytic inactivation was observed in presence of various anions (HCO3¯ , SO4 2¯ , Cl¯ and NO3¯ ) and cations (Na, K, Caand Mg). Even a small addition of H2O2 was observed to improve the photocatalytic inactivation. At higher dosage of H2O2, a 2 min exposure was sufficient to result in a complete inactivation. Changing the initial pH of the solution was observed to have no significant effect on the photocatalytic inactivation. All the combustion synthesized catalysts showed higher activity as compared to those obtained with commercial Degussa P-25 TiO2 in presence of visible light. The higher photocatalytic activity of combustion synthesized TiO2 can be attributed to the lesser crystallite size, higher surface area, large amount of hydroxyl groups and decreased band-gap energy of the catalyst. The present study demonstrates the potential use of catalyst immobilized thin films for the photocatalytic inactivation of E. coli in the presence of UV light. The CS-TiO2 catalyst was immobilized on glass substrate by LbL deposition technique. The performance of immobilized CS-TiO2 was compared to commercial Degussa Aeroxide TiO2 P-25 (Aeroxide) catalyst. The effect of various operating parameters like catalyst loading, surface area and number of bilayers on inactivation has been investigated. It was observed that increasing the number of bilayers and the concentration did not influence the inactivation but increased surface area led to an increase in inactivation. It was observed that the catalyst immobilized on glass slides can be used for repeated experimental cycles with the same efficiency. It was observed that the inactivation process can be studied in continuous mode by using catalyst immobilized on glass beads. The work also focused attention towards understanding the microorganism inactivation mechanism and kinetic aspects. Various microscopy techniques such as optical microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to study the inactivation mechanism. From the images obtained, it was suggested that the inactivation is caused due to rupture of cell wall. The mechanism was also examined by carrying out degradation experiments on cell component such as protein and media component such as dextrose. UV alone was observed to degrade protein and the presence of catalyst showed no additional effect. On the other hand, dextrose does not respond to photocatalytic degradation even at a lower concentration. The photocatalytic degradation of Orange G dye was reduced by addition of dextrose sugar or protein which shows a possibility of competitive degradation. The kinetics of inactivation was studied by various models available in literature such as the power-law model, Chick-Watson model, modified Hom model, GInaFIT tool and a Langmuir-Hinshelwood type model. It was observed that power-law based kinetic model showed good agreement with the experimental data. A mechanistic Langmuir-Hinshelwood type model was also observed to model the inactivation reactions with certain assumptions.

Microorganisms and drops are ubiquitous in nature: while drops can be found in sneezes, ink-jet printers, oceans etc, microorganisms are present in our stomach, intestine, soil, oceans etc. In most situations they are present in complex conditions: drop spreading on a rigid or soft substrate, drop covered with impurities that act as surfactants, marine microbe approaching a surfactant laden drop in density stratified oceanic waters in the event of an oil spill etc. In this thesis, we extract the physics underlying the influence of two such complicated effects (surfactant redistribution and density-stratification) on the motion of drops and swimming microorganisms when they are in isolation or in the vicinity of each other. This thesis is relevant in understanding the bioremediation of oil spill by marine microbes.<div><br></div><div>We divide this thesis into two themes. In the first theme, we analyze the motion of motile microorganisms near a surfactant-laden interface in homogeneous fluids. We begin by calculating the translational and angular velocities of a swimming microorganism outside a surfactant-laden drop by assuming the surfactant is insoluble, incompressible, and non-diffusing, as such system is relevant in the context of bioremediation of oil spill. We then study the motion of swimming microorganism lying inside a surfactant-laden drop by assuming the surfactant is insoluble, compressible, and has large surface diffusivity. This system is ideal for exploring the nonlinearities associated with the surfactant transport phenomena and is relevant in the context of targeted drug delivery systems wherein one uses synthetic swimmers to transport the drops containing drug. We then analyze the motion of a swimming organism in a liquid film covered with surfactant without making any assumptions about the surfactant and this system is relevant in the case of free-standing films containing swimming organisms as well as in the initial stages of the biofilm formation. In the second theme, we consider a density-stratified background fluid without any surfactants. In this theme, we examine separately a towed drop and a swimming microorganism, and find the drag acting on the drop, drop deformation, and the drift volume induced by the drop as well as the motility of the swimming microorganism.</div>

Les systèmes de biorétention sont de plus en plus utilisés pour gérer le ruissellement des eaux pluviales urbaines. Bien que les plantes soient une composante essentielle des biorétentions, il existe à ce jour peu de preuves de la contribution des espèces choisies, en particulier dans les climats tempérés à grande variation saisonnière. Aussi, les bactéries et les champignons peuvent jouer un rôle majeur dans la performance des biorétentions en améliorant la qualité de l'eau ou en soutenant l'efficacité des plantes. Mais à ce jour, on sait peu de choses sur les microorganismes peuplant les biorétentions et encore moins sur l'influence des choix de conception de ce système et ses conséquences sur la contribution de ces organismes. D’autre part, en climat froid, l'utilisation de sels de déglaçage génère des ruissellements salins qui pourraient affecter les performances des biorétentions, notamment en impactant les processus biologiques en cours dans le système. Le but de mon étude était de comparer la contribution de la végétation à la performance des biorétentions en fonction de l'espèce plantée, de tester l'impact du ruissellement salin sur l'hydrologie et la filtration des contaminants par le système en fonction des espèces végétales utilisées, et de caractériser l'influence de ces 2 facteurs sur la diversité, la composition et l'abondance relative des bactéries et champignons au sein des biorétentions. J’ai réalisé une expérience en mésocosmes avec 4 espèces végétales couramment utilisées en biorétention et couvrant un large éventail de types biologiques (Cornus sericea, Juncus effusus, Iris versicolor, Sesleria autumnalis). Pour simuler un ruissellement printanier chargé en sel de déglaçage, l'eau de ruissellement semi-synthétique utilisée pour l'irrigation à était complétée au printemps avec quatre concentrations de NaCl (0, 250, 1000 ou 4000 mg Cl/L). Le séquençage des gènes 16S et ITS ont été utilisé comme indicateur de diversité, de composition et d'abondance relative bactérienne et fongique. En général, tous les mésocosmes de biorétention ont significativement réduit les volumes d'eau, les débits de pointe et les charges de contaminants. Certaines plantes améliorent significativement les performances en augmentant la perte d'eau par évapotranspiration pendant la période de croissance (jusqu'à 2,5 fois) et en réduisant le débit d'eau (jusqu'à 2,7 fois). Les plantes ont amélioré l’enlèvement des macronutriments, avec un enlèvement massique moyen de 55 % pour l’Azote total, 81 % pour le Phosphore total et 61 % pour le K, contre -6 % (relargage), 61 % et 22 % respectivement pour les non plantés. À l'exception des Sesleria, l’enlèvement des éléments traces par les mésocosmes plantés était généralement plus élevée que chez les non plantés (jusqu'à 8,7 %). Leur niveau de contribution suivait le même ordre que leur taux d'évapotranspiration et leur taille globale (Cornus > Juncus > Iris > Sesleria). Même à la concentration la plus élevée de NaCl testée, aucun effet sur la réduction du volume d'eau et les débits n'a été détecté. En revanche, le ruissellement chargé en sel a temporairement augmenté l’enlèvement de certains métaux tels que Cr, Ni, Pb et Zn. Dans l’ensemble, les plantes ont très bien toléré le passage du ruissellement chargé de sel au printemps. Tous les mésocosmes ont naturellement été colonisés par des bactéries et des champignons adaptés à un environnement humide et contaminé. Parmi les taxons dominants, plusieurs ont des fonctions en lien avec la performance des biorétentions, telles que l'implication dans le cycle de l'azote, la dégradation des hydrocarbures, la tolérance et la remédiation de métaux, ou des symbiotes végétaux. Ma thèse souligne l'importance du choix des espèces végétales sur la performance des biorétentions. D’une part en raison de leur contribution différentielle à la réduction du volume d'eau, des débits de pointe et l'enlèvement des contaminants, en particulier des macronutriments, et d’autre part à cause de leur influence sur la composition et l’abondance des microorganismes. Même si plusieurs des bactéries et champignons dominants ce système auraient la capacité de contribuer à la performance des biorétentions, d’autres études devront être menées pour vérifier leur activité. Finalement, ma thèse a démontré que la présence de sel de déverglaçage dans le ruissellement ne devrait pas être un frein à la mise en place de cellules de biorétention, puisque qu'aux concentrations habituellement observées à la suite d’épandages, aucun effet négatif sur la performance, la végétation ou les communautés bactérienne et fongique n’a été observé dans la présente thèse. Cependant, la libération des cations structurants du sol et l’exfiltration du sels devrait être faire l’objet d’un suivi à plus long terme. Bien que ces expériences aient permis d'analyser l'effet des espèces végétales et des sels de déverglaçage sur la réduction du volume d'eau, des débits de pointe, l’enlèvement des contaminants, et les micro-organismes, l'extrapolation de ces résultats à grande échelle doit être effectuée avec prudence. En effet, les mésocosmes sont des systèmes artificiels qui ne reproduisent pas entièrement les conditions réelles des biorétentions à grande échelle, notamment en ce qui concerne les températures hivernales inférieures à zéro, et ne sont étudiés qu’un lapse de temps. Aussi, les biorétentions réelles sont rarement plantées en monoculture, de sorte que les interactions entre les espèces végétales et les microorganismes pourraient influencer la performance du système. Pour une application réussie des conclusions de cette étude à l'échelle pratique, il serait essentiel que des projets pilotes valident ces résultats. / Bioretention systems are increasingly used to manage urban stormwater runoff. Plants are an essential component of bioretention, improving water quality and reducing runoff volume and peak flows. Although plants are an essential component of bioretentions, there is little evidence on how their contribution changes according to the species chosen, especially in temperate climates with large seasonal variations. In addition, bacteria and fungi could play a major role in bioretention performance by improving water quality or supporting plant efficiency. But to date, little is known about the microorganisms living in bioretentions and even less about the influence of the design choices of this system and therefore its consequences on the contribution of these organisms. In cold climates, the use of de-icing salts generates saline runoff which could affect the bioretentions performance, especially by reducing biological processes. The aim of my study was to compare the contribution of vegetation to the performance of bioretentions according to the species planted, to test the impact of saline runoff on the hydrology and the filtration of contaminants by the system according to the plant species used, and to characterize the influence of these 2 factors on the diversity, composition and relative abundance of bacteria and fungi within bioretentions. I performed a mesocosm experiment with 4 plant species commonly used in bioretention and covering a wide range of biological types (Cornus sericea, Juncus effusus, Iris versicolor, Sesleria autumnalis). To simulate spring salt-laden runoffs, the semi-synthetic runoff water used for irrigation was supplemented in spring with four concentrations of NaCl (0, 250, 1000 or 4000 mg Cl/L). Sequencing of 16S and ITS genes was used as bacterial and fungal diversity, composition and relative abondance indicator. In general, all bioretention mesocosms significantly reduced water volumes, peak flows, and contaminant loads. Some plants significantly increased the performances, by increasing water loss through evapotranspiration during the growing period (up to 2.5 times) and reducing water flow (up to 2.7 times). Plants improved macronutrients removal, with an average mass removal of 55% for total nitrogen, 81% for total phosphorus and 61% for K compared to –6% (release), 61% and 22% respectively for the unplanted. Except for Sesleria, mass removal of trace elements in planted mesocosms was generally higher than in unplanted ones (up to 8.7%). Their contribution level followed the same order as their evapotranspiration rate and overall size (Cornus > Juncus > Iris > Sesleria). Even at the highest concentration of NaCl tested, no impact on water volume reduction and flow rates were detected. In contrast, salt-laden runoffs temporarily increased removal of some metals such as Cr, Ni, Pb, and Zn. Overall, the plants tolerated the passage of salt runoff in spring. All bioretention mesocosms were naturally colonized by bacteria and fungi adapted to a humid and contaminated environment. Among the dominant taxa, several described functions related to the bioretention performances, such as involvement in the nitrogen cycle, the degradation of hydrocarbons, the tolerance and remediation of metals, or plant symbionts. My thesis emphasizes the importance of the plant species choice on the bioretentions performance. firstly because of their differential contribution to the water volume reduction, peak flows, and the contaminants removal, in particular macronutrients, secondly through their influence on the composition and abundance of microorganisms. Even though several of the dominant bacteria and fungi found would have the ability to contribute to the performance of bioretentions, further studies will be needed to verify their activity. Finally, my thesis demonstrated that the presence of de-icing salt in the runoff should not be a hindrance to the bioretention cells implementation, since at concentrations usually observed following salt spreading, no negative effect on the bioretentions performance, on the vegetation or the bacterial and fungal communities were observed in this thesis. However, the release of soil-structuring cations as well as salts exfiltration should be monitored in the longer term. Although these experiments allowed for the analysis of the effect of plant species and de-icing salts on the reduction of water volume, peak flow rates, contaminant removal, and microorganisms, the extrapolation of these results to a larger scale must be done with caution. Despite the advantage of characterizing the performance of bioretention in mesocosms in terms of replication and factor control, it is important to recognize that this approach also has its limitations. Mesocosms are artificial systems that do not fully replicate the real-world conditions of large-scale bioretention, especially concerning sub-zero winter temperatures and the limited time frame of study. The size of the mesocosms could lead to edge effects, such as preferential flows, while real-world scenarios involve slopes that create heterogeneous conditions within these basins, influencing factors like frequency and quantity of water received. Additionally, real bioretention systems are seldom planted as monocultures, thus interactions between plant species and microorganisms may impact system performance. For successful implementation of the findings of this study on a practical scale, validation through pilot projects would be essential.

Der Klimawandel bedroht Ökosysteme auf der ganzen Welt. Besonders der Anstieg in Länge, Intensität und Häufigkeit von Dürren kann bedeutenden Einfluss auf den globalen Kohlenstoffkreislauf haben. Die Frage, ob Pflanzen und Mikroorganismen anfällig gegenüber ökologischem Stress wie Dürren sind, wurde bereits in vielen Studien für verschiedene Ökosysteme und mit verschiedenen Ansätzen untersucht, aber Analysen von Dürreauswirkungen, die ober- und unterirdische Interaktionen von Pflanzen und Mikroorganismen mit einbeziehen, sind eher selten. Deshalb wird in der vorliegenden Studie die Frage erörtert, wie Trockenheit und/oder Hitze die Interaktionen von Pflanzen und Mikroorganismen in Bezug auf ihre Kohlenstoff-Verbindung beeinflussen. Dies dient zur Bestimmung der Stärke der Pflanze-Mikroorganismen-Kohlenstoff-Verbindung, wenn das Ökosystem an seine Grenzen gebracht wird. Der Fokus liegt deshalb auf durch Trockenstress und Hitze hervorgerufenen Veränderungen in der ober-unterirdischen Kohlenstoff-Dynamik in zwei vom Klimawandel bedrohten Ökosystemen. Es wurde untersucht, wie extreme Klimaereignisse, deren Häufigkeit in Zukunft weiter ansteigen soll, die Kohlenstoff-Verbindung zwischen Pflanzen und Mikroorganismen beeinflusst und wie mikrobielle Gemeinschaften unter diesen Umständen reagieren, um die Resistenz und Reaktionsmechanismen von Ökosystemen im zukünftigen Klimawandel besser vorhersagen zu können. In Kapitel 4 wurde ein Buchenwaldunterholz-Ökosystem untersucht. Buchenwaldmonolithen wurden einem extremen Klimaereignis (Trockenheit und/oder Hitze) ausgesetzt. Die Stärke der Pflanze-Mikroorganismen-Kohlenstoff-Verbindung und Veränderungen in der mikrobiellen Gemeinschaftsstruktur und -aktivität wurden mithilfe von stabilen 13C Isotopenmethoden und Ansätzen auf molekularer Basis, wie 16S rRNA- und Phospholipid-Analysen, bestimmt. In Kapitel 5 wurde ein kleines aquatisches Ökosystems untersucht. Zwei emerse aquatische Makrophyten, Phragmites australis und Typha latifolia, wurden in einem Mesokosmos-Experiment mit Sediment aus einem Soll einer einmonatigen Dürre ausgesetzt. Mithilfe einer 13CO2 Pulsmarkierung, sowie PLFA- und nicht-strukturbildenden Kohlenhydrat-Analysen wurde Kohlenstoff von den Blättern in die Wurzeln bis ins Sediment verfolgt, wo er teilweise in mikrobielle Phospholipide eingebaut wird. Diese Studie hat gezeigt, dass die zwei untersuchten Ökosysteme Trockenstress und Hitze relativ gut widerstehen können, zumindest kurzfristig, und dass das Kohlenstoff-Kontinuum, beziehungsweise die Verbindung zwischen ober- und unterirdischen Gemeinschaften, auch unter starkem Stress intakt bleibt. Zusammenfassend scheint es, dass Ökosysteme stark von einem funktionierenden Pflanze-Boden/Sediment-Mikroorganismen Kohlenstoff-Kontinuum abhängen und versuchen, es auch unter starkem Stress zu erhalten, was möglicherweise dazu beiträgt, dem Anstieg von extremen Dürreperioden aufgrund des Klimawandels besser zu widerstehen. / Climate change is threatening ecosystems around the world. Especially the increase in duration, intensity, and frequency of droughts can have a considerable impact on the global carbon cycle. The question whether plants and microbes are susceptible to environmental stress like drought has been assessed in many studies for different ecosystem types and by using numerous approaches, but research on drought effects that includes above- and belowground interactions is rather scarce. Therefore, the present study assesses the question of how drought and/or heat influence the interactions of plants and microbes, especially the carbon coupling, in order to determine the strength of plant-microbe carbon linkages when an ecosystem is pushed to its limits. The focus of this study thus lies on changes in aboveground-belowground carbon dynamics and the subsequent effects on the soil microbial community under drought and/or heat stress in two climate-threatened ecosystems. It was evaluated how extreme climate events, that are predicted to be more frequent in the near future, affect the carbon coupling between plants and microorganisms and how microbial communities respond under these circumstances, in order to be able to better predict ecosystem resistance and response mechanisms under future climate change. In chapter 4 a beech forest understory ecosystem was investigated. An extreme climate event (drought and/or heat) was imposed on beech forest monoliths and the strength of the plant-microbe carbon linkages and changes in the microbial community structure and activity were determined by using stable 13C isotope techniques and molecular-based approaches like 16S rRNA and microbial phospholipid-derived fatty acid (PLFA) analysis. In chapter 5 a small aquatic ecosystems was investigated. Two emergent aquatic macrophytes, Phragmites australis and Typha latifolia, were grown on kettle hole sediment and then exposed to a month-long summer drought in a mesocosm experiment. By conducting a 13CO2 pulse labeling as well as PLFA and non-structural carbohydrate analyses, the fate of carbon was traced from the plant leaves to the roots and into the sediment, where some of the recently assimilated carbon is incorporated into microbial PLFAs. Overall, this study showed that the two investigated ecosystems can endure environmental stress like heat and drought relatively well, at least in the short-term, and that the carbon continuum, or the linkage between above- and belowground communities, remained intact even under severe stress. In conclusion, it seems that ecosystems strongly depend on and try to maintain a functional plant-soil/sediment microorganism carbon continuum under drought, which might help to withstand the increase in extreme drought events under future climate change.

No description available.

År 2020 drabbades världen av Covid-19. Spridningen av viruset resulterade i att många länder upprättade en lockdown. Detta påverkade sjöfartsbranschen negativt och ställde till med problem när folk blev sjuka. Detta är på grund av den unika miljön som finns ombord på fartyg. Syftet med studien var att analysera och utvärdera hur olika fartyg och rederier agerade under covid-19-pandemin med fokus på effektivitet, framgång och problem när det kommer till smittskydd. Studiens frågeställningar berörde hur rederiers existerande smittskyddsplaner såg ut och huruvida de kan förbättras, vilka lärdomar som kan dras om smittspridning ombord på fartyg och huruvida en förbättrad smittskyddsplan kan konstrueras utifrån de som redan existerar. En kvalitativ metod i form av granskning och inläsning av studier i området smittspridning i allmänhet samt studier om utbrott av covid-19 ombord på fartyg. Smittskyddsplaner samlades in genom ett mailutskick till svenska rederier. Resultatet visar att rederierna efterlevde många av WHO:s riktlinjer där de även implementerade egna tillägg till den ombordhavna smittskyddsplanen. Vi kom även fram till att landbaserad assistans är en viktig komponent för att kunna bekämpa smittspridning ombord. / In 2020, the world was struck by Covid-19. The spread of the virus resulted with many countries establishing  lockdowns. This negatively affected the shipping industry and caused problems when people got sick. This is because of the unique environment that exists on board ships. The purpose of the study was to analyze and evaluate how different ships and shipping companies acted during the COVID-19 pandemic with a focus on efficiency, success and problems when it came to controlling the spread of infections. The study's questions concerned how shipping companies' infection control plans were complied with and whether they can be improved, what lessons can be learned about the spread of infections on board ships and whether an improved infection control plan can be constructed from those that already exist. A qualitative method of reviewing and reading studies in the field of infection control in general and studies on COVID-19 outbreaks on board ships. Infection control plans were collected through a mailing to Swedish shipping companies. The results showed that the shipping companies complied with many of the WHO's guidelines where they also implemented their own additions to the on-board infection control plan. We also came to the conclusion that land-based assistance is an important component for combating the spread of infections on board.