Orientador: Maria Silvia Viccari Gatti / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-16T08:58:49Z (GMT). No. of bitstreams: 1 Fregolente_MariaClaraDuarte_D.pdf: 7203529 bytes, checksum: acf60e6e770f96882a60213754fcb52d (MD5) Previous issue date: 2010 / Resumo: Picobirnavírus (PBV) pertencem à família Picobirnaviridae, gênero Picobirnavirus e têm como espécie tipo Human picobirnavirus e Rabbit picobirnavirus. Estes pequenos vírus não envelopados, de dois segmentos genômicos de RNA dupla fita, são encontrados em amostras de fezes diarreicas ou não de diferentes hospedeiros mamíferos, incluindo o homem, aves e répteis. Os mecanismos da infecção por PBV e sua associação a gastroenterites ainda não estão esclarecidos, mas são colocados como agentes emergentes e oportunistas e seu potencial zoonótico foi sugerido. As técnicas utilizadas para a identificação desses vírus são: eletroforese em gel de poliacrilamida (EGPA) e RT-PCR. A primeira permite diferenciar os PBV pelas diferenças de migração dos seus segmentos genômicos. Já na RT-PCR são sete os pares de iniciadores descritos, incluindo aqueles que permitem sua diferenciação em genogrupo I ou II. Este projeto objetivou caracterizar genética e filogeneticamente PBV de diferentes hospedeiros naturais e as estratégias utilizadas foram o sequenciamento total e parcial dos segmentos genômicos de PBV e a definição de uma região conservada para o desenho de iniciadores capazes de diagnosticar todos os PBV por RT-PCR. Foram analisadas para a presença de PBV amostras de fezes de suínos, coelhos, ratos, cães, cobras, ratos silvestres, capivaras, cavalos e bovinos. Utilizando a EGPA, PBV foram identificados em todos os hospedeiros estudados e pela RT-PCR identificou-se genogrupo I de PBV em quase todos, com exceção de capivaras e bovinos. O genogrupo II não foi identificado. A circulação do genogrupo I em diferentes hospedeiros sugere que não existe especificidade genogrupo-espécie de hospedeiro. O sequenciamento parcial do segmento menor dos PBV identificados em cães, cobra e ratos mostrou uma relativa homologia principalmente com sequências de PBV identificados em humanos. A coexistência de duas ou mais populações de PBV em um mesmo hospedeiro foi identificada em cavalos, suínos, rato, rato silvestre e coelho a partir do sequenciamento parcial do segmento menor após clonagem, sugerindo um possível mecanismo de reassortment, o que pode levar a salto entre espécies. Esses resultados suportam o potencial emergente e zoonótico dos PBV. A heterogeneidade nas sequências de nucleotídeos verificada por esse sequenciamento sugere a presença de quasiespécies de PBV nesses hospedeiros. A menor variação observada nas sequências de nucleotídeos de PBV identificados em animais não confinados pode ser justificada pela tendência ao menor contato entre esses animais do que entre os de cativeiro, fazendo com que a transmissão viral também seja menor. Foi proposta uma padronização para a nomenclatura dos PBV, baseada em seu hospedeiro, país e ano de identificação. O atual sistema de classificação para os PBV não é apropriado, devido à identificação de PBV não pertencentes a nenhum dos genogrupos já descritos e à presença de heterogeneidade nas sequências de PBV do genogrupo I. Infelizmente, não foi possível sequenciar o genoma completo dos PBV estudados, não sendo identificada nenhuma sequência conservada que permitisse o desenho de iniciadores capazes de unificar o diagnóstico dos PBV. Estudos tentativos estão em andamento para que, a partir do sequenciamento completo e análise do genoma de diferentes PBV, seja possível definir as porcentagens de identidade mínimas para sua classificação em genogrupos e/ou genotipos / Abstract: Picobirnaviruses (PBV) belong to the Picobirnaviridae family, genus Picobirnavirus, and Human picobirnavirus and Rabbit picobirnavirus are the type species. These small non-enveloped viruses, with two genetic segments of double-stranded RNA, can be found in diarrheic or nondiarrheic fecal samples from different hosts like mammals, including humans, birds and reptiles. PBV infection and its association with gastroenteritis are still unknown, but they are considered opportunistic and emergent pathogens, and their zoonotic potential has also been suggested. Techniques for PBV identification include: polyacrylamide gel electrophoresis (PAGE) and RTPCR. The first one allows characterization of PBV according to the migration pattern of their genomic segments. In the RT-PCR, seven primers' pairs have been designed, including one that allows classification of PBV into genogroups I or II. The aim of this project was the genetic and phylogenetic characterization of PBV identified in fecal samples from different natural hosts by complete and partial sequencing of PBV genomic segments and set up of a conserved region for designing primers able to detect all PBV by RT-PCR. Fecal samples from pigs, rabbits, rats, dogs, snakes, wild rats, capybaras, horses and cattle were analyzed for PBV occurrence. PBV were identified in all studied hosts by PAGE and genogroup I was identified in the majority of them by RT-PCR, except in capybaras and cattle. Genogroup II was not identified. Genogroup I circulation in different hosts suggests that there is no genogroup-host species' specificity. Partial sequencing of small PBV's genomic segment identified in fecal samples from dogs, snake and rats showed homology mainly to human PBV sequences. Coexistence of two or more PBV population in the same host could be determined in fecal samples from horses, pigs, rat, wild rat and rabbit by partial sequencing of small PBV's genomic segment after cloning, suggesting that reassortment may occur in nature, allowing host species jump. These results support the emergent and zoonotic potential of PBV. The heterogeneity found in PBV's nucleotide sequences after cloning suggests the existence of PBV quasispecies in these hosts. The little variation in nucleotide sequences of PBV identified in hosts living in an open environment could be justified by a tendency of less contact among these animals, allowing less viral spread. The classification system used nowadays is cannot be considered appropriated as it doesn't consider the heterogeneity found in PBV's genogroup I sequences. Also, PBV that don't belong to any of the described genogroups, remain with no classification. Therefore, a new standard nomenclature for PBV, based on its host, country and year of identification was proposed. Unfortunately, it was not possible to sequence the complete genome of PBV found in this study. Also, no conserved sequence could be identified for primers' design, which would be capable of standardized PBV detection. Additional studies are ongoing to try to define nucleotide sequences identity percentages for genogroups and/or genotypes classification / Doutorado / Microbiologia / Doutor em Genetica e Biologia Molecular

In recent years, a new wave power of sharing economy, or known as collaborative consumption has emerged in accommodation, and tourism marketplaces (Guttentag, 2015). Airbnb is one of the most talked-about among the sharing hospitality companies, which is an online marketplace and a platform connecting worldwide travelers with local hosts somewhere. Although Airbnb has two types of users, guests and hosts, in current studies of Airbnb hosts, most researchers focus on the hosts from a business perspective. This study aimed to identify and understand hosts’ motivations to start the Airbnb business, and the benefits and challenges in a host’s experience. The informal interview was the method for the study, and data were processed by thematic analysis. The results find that motivations varied from host to host when sharing nature in common. The benefits overweighed the challenges in each host’s experience since participants could gain economic benefits (extra income), mental health (brain exercise for old hosts) and well-being (cross-cultural social learning) in sharing economy. Worries about security and extra physical work did not bother most hosts, and the effects of a tax on Airbnb hosts were not obvious.

Comparative cytogenetics of the bed bug Cimex lectularius (Heteroptera: Cimicidae) The human bed bug Cimex lectularius has started enormous spreading to all developed countries of temperate climate zone during the last ten years. Bed bug was almost eradicated by a mass use of DDT in these areas until the 70's in the 20th century. This temporal haematophagous ectoparasite occupies particularly human dwellings and bat roosts. Cimex lectularius shows unusual combination of cytogenetic characteristics, general for all Heteroptera, however, not usual for other organisms. The chromosomes are holokinetic, with completely achiasmatic meiosis and inverted meiosis of the sex chromosomes. Especialy remarkable feature is intraspecific variation of the number of the X chromosomes. The variable number of chromosomes of 43 populations of Cimex lectularius from the Czech Republic and 27 populations from other European countries was studied in the present study. The 10 variants of karyotype were found out by using the "hotplate spreading" method and the standard Giemsa staining. There were male karyotypes with 2n = 29, 30, 31, 32, 33, 34, 35, 37, 42 and 47 chromosomes and two females with peculiar odd number of sex chromosomes X, 2n = 33 and 43, not complementary with any male. A stable number of 2n = 26 autosomes...

Viruses hold our attention for the horrific impact they have on human health and welfare. However, viruses are a critical part of our ecosystem and facilitate the cycling of carbon and other important nutrients. The cycle of virus infection, followed by host resistance and the subsequent evolution of new strains enables adaptation to changing hosts and the environment. Giant viruses, some with particle sizes large enough to be visible in light microscopes and their bewildering array of accessory genes, have captivated scientists and the general public since their discovery two decades ago. Giant viruses are part of the Nucleocytoviricota (NCV) whose members include both harmful agents (such as the causative agents of smallpox and swine hemorrhagic fever) and beneficial ones (such as those that provide biocontrol of insects, mitigation of toxic algal blooms and enzymes for biotechnology). Most of the giant viruses discovered, to date, are from marine and freshwater ecosystems where their hosts are abundant. In terrestrial soils, very few giant viruses have been revealed because of challenges in shifting through the astounding microbial genetic diversity in soil to assemble genomes from metagenomic data. Currently there is a lack of knowledge about abundance and genetic diversity of giant viruses in terrestrial soils, knowledge about their hosts and their influence on biogeochemical cycling. In 2018, giant viruses were discovered in the Barre Woods experimental warming plots at Harvard Forest. (Schulz et al 2018 Nature Communications). A novel environmental genomics approach involving filtration and fluorescence activating cell-sorting (FACS) was used to discover 16 Nucleocytoviricota (NCVs) in just a few grams of Harvard Forest soil. All these newly discovered viruses represent distinct lineages (new species, genera, and families). This experiment involved just two soil cores (1 warming and 1 control) and a single time point at Harvard Forest. There is much to learn about the terrestrial giant virus genetic biodiversity as these same viruses have not yet been discovered at other sites around the world. My research will focus on a genus of giant viruses with only three known representatives, all from Harvard Forest. They are Hyperionvirus (with the world’s 2nd largest virus genome at 2.4 MBp), Terrestrivrus the 10 th largest genome at 1.8 MBp), and Harvfovirus (the 15 th largest genome at 1.6 MBp). In the experimental warming plots the relative amount of bacteria to fungi has increased. We hypothesize that the relative increase in bacteria has led to an increase in protists, which feed on the bacteria, which in turn has led to an increase in giant viruses, which infect the protists. Because of the high genetic diversity in viruses and the lack of ribosomal genes, it is not possible to create primers that span the entire Nucleocytoviricota phylum or even at the family level. To test our hypothesis, we designed degenerate PCR primers that detect and quantify members of the genus containing the 3 giant Harvard Forest viruses. DNA was extracted from soil samples the soil (stored at -80C) from the 2017 temperature toggle experiment at Barre Woods in which the power to the warmed plots was turned off from late May until early September were used. The giant viruses were originally discovered in the sample just prior to turning off the power. We used 4 time points spanning the experiment with 8 samples from each the warmed and control plots (4 x 16 = 16 samples total). The primers were designed based on five hallmark genes that are present in most members of the Nucleocytoviricota. After amplification, the amount of DNA would be quantified and normalized. We expect to better understand the genetic diversity of this genus of giant viruses in the soil including the possibility of detecting new species in this genus.

The brown marmorated stink bug, Halyomorpha halys (Stål), is an invasive species that has spread throughout the United States and become a serious agricultural pest. Studies were conducted in Virginia on the survival of H. halys nymphs on different vegetable hosts and on the oviposition preference of H. halys on common tree hosts in southwestern Virginia. To determine the effects of vegetable host on H. halys survival, nymphs were placed on one of five vegetable host plants and their corresponding vegetable fruit. Survival was highest on sweet corn, followed by bell pepper and snap bean. Eggplant and tomato were poor compared to other vegetable hosts tested, potentially due to secondary compounds released by the plant to reduce feeding. Of six common host trees sampled, H. halys laid the most egg masses on catalpa, Catalpa bignonioides, while aggregation lure had no effect on the number of eggs laid. Across host trees, egg masses were more commonly found in trees with fruiting structures present. An additional study was conducted on a red-sternum phenotype of H. halys. Mortality was recorded by sternum phenotype for each sex. There was no difference in survival between groups at two time points. Biochemical tests were used to determine if the red-sternum was associated with the potentially pathogenic red bacteria Serratia marcescens. Only one stink bug's gut contents had a confirmed infection of S. marcescens. Results from these studies offer insight into H. halys development on vegetable hosts and oviposition preferences on different host trees. / MSLFS / The brown marmorated stink bug (BMSB), is an invasive insect that has spread throughout the United States and become a serious pest. Current research is focused on reducing their populations without increasing insecticide use. Studies were conducted to determine if vegetable host type influenced survival and development of this insect. Nymphs were placed on one of five vegetable plants with the corresponding vegetable fruit. Overall, survival was highest on sweet corn, followed by bell pepper and snap bean. Eggplant and tomato were poor hosts, potentially due to chemicals released by the plant to reduce insect feeding. Six common host trees of BMSB were sampled to determine where females lay the most egg masses and the effect of using an attraction lure. Catalpa trees had the most egg masses throughout the season. Use of a lure had no effect on the number of eggs laid on any tree. A red colored abdomen was observed in some adult insects throughout these studies. To determine if this was associated with higher mortality, male and female insects were observed for two weeks. There were no mortality differences at either seven or 14 days between any of the groups. Tests were used to determine if the red abdomen was caused by a red-colored bacterium. Of the insects sampled, there was only one stink bug with a confirmed infection. Results from these studies provides information that increases knowledge of this pest’s ecology in Virginia.

Sabe-se que humanos, plantas e animais são colonizados por uma elevada diversidade de microrganismos e que esses organismos eucariotos dependem destes microrganismos para manutenção do seu desenvolvimento. Usando dois modelos de associação microrganismo-hospedeiro, foi testado a hipótese de que hospedeiros pertencentes a domínios da vida distintos, apesar de suas particularidades estruturais, genotípicas, filogenéticas e fisiológicas, compartilham similaridades nos modos de associação com a comunidade bacteriana. Sendo assim, o objetivo do presente trabalho foi mapear a comunidade bacteriana associada a plantas do gênero Anthurium endêmicas e/ou não. Paralelamente, mapear a comunidade bacteriana associada a gêneros distintos de cianobactérias, ao longo da curva de crescimento e quando esta é submetida a condições de cultivo distintas. Como resultados, primeiramente, foi observado que plantas Anthurium alcatrazense endêmicas da Ilha apresentam riqueza e diversidade menor que as plantas da espécie Anthurium loefgrenii coletada na ilha de Alcatrazes e também menor que as plantas Anthurium intermedium e Anthurium pentaphyllum coletadas na região de continente. Também foi observado que a estrutura da comunidade bacteriana associada as plantas de A. alcatrazense é distinta quando comparada com as plantas coletadas no continente e também da própria ilha de Alcatrazes. Essa dissimilaridade foi principalmente representada por OTUs afiliadas à Betaproteobacteria e Gammaproteobacteria. Esses resultados sugerem especificidade microrganismo-hospedeiro. Considerando a associação cianobactéria e bactérias heterotróficas, os resultados demonstraram que a comunidade bacteriana associada é especifica de acordo com o gênero de cianobactéria, composta principalmente por classes apresentando abundância relativa de sequencias distintas como, Betaproteobacteria, Gammaproteobacteria, Flavobacteria e Cytophagia. Por outro lado, foi possível observar que ao longo das fases de multiplicação da linhagem Microcystis aeruginosa, ocorre uma sucessão de grupos bacterianos, sendo principalmente representado pela variação da abundância de Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria e Flavobacteria relativo a fase estacionaria de multiplicação. Quando submetida em condições de cultivo distintas, foi possível observar que variações nas taxas de multiplicação da cianobactéria influenciaram uma modulação da estrutura da comunidade bacteriana associada, desta forma sugerindo que rápidas alterações na estrutura da comunidade bacteriana associada a M. aeruginosa, é resultado de processos de auto-regulação entre cianobactéria e bactérias heterotróficas associadas. De forma geral, pode-se sugerir que hospedeiros distintos apresentam padrões de associações com as bactérias similares, podendo estas similaridades sugerir estratégias para um melhor entendimento e manejo dos ecossistemas. / It is known that humans, plants and animals are colonized by a high diversity of microorganisms and that these eukaryotic organisms depend on these microorganisms to maintain their development. Using two microorganism-host association models, we hypothesized that hosts belonging to distinct domains of life, despite their structural, genotypic, phylogenetic and physiological particularities, share similarities in the modes of association with the bacterial community. Thus, the objective of this work was to map the bacterial community associated with plants of the genus Anthurium endemic and / or not. In parallel, map the bacterial community associated with distinct genera of cyanobacteria, along the growth curve of and when it is submitted to different culture conditions. In this context, we observed that Anthurium alcatrazense plants endemic to the Island, present less richness and diversity than the plants of the species Anthurium loefgrenii collected in the island of Alcatrazes and smaller than the plants Anthurium intermedium and Anthurium penthaphyllum collected in the continent. We found that the structure of the bacterial community associated with the plants of A. alcatrazense is distinct when compared to the plants collected in the continent and island of Alcatrazes itself. This dissimilarity was mainly represented by OTUs affiliated with Betaproteobacteria and Gammaproteobacteria. These results suggest microorganism-host specificity. Considering the association cyanobacteria and heterotrophic bacteria, the results demonstrated that the associated bacterial community is specific according to the genus of cyanobacteria, composed mainly by abundance distinct from those of classes, Betaproteobacteria, Gammaproteobacteria, Flavobacteria and Cytophagia. On the other hand, it was possible to observe that during the multiplication stages of the Microcystis aeruginosa strain, a succession of bacterial groups occurs, mainly represented by the variation of the abundance of Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria and Flavobacteria relative to the stationary phase of multiplication. When submitted under different culture conditions, it was possible to observe that variations in cyanobacteria multiplication rates influenced a modulation of the associated bacterial community structure, thus suggesting that rapid changes in the bacterial community structure associated with M. aeruginosa is a result of processes of self-regulation between cyanobacteria and associated heterotrophic bacteria. In general, distinct hosts show patterns of associations with similar bacteria, and these similarities may suggest strategies for a better understanding and management of ecosystems.

Plantas de mostarda-do-campo (Brassica rapa) exibindo intenso superbrotamento de ramos finos, com folhas e flores de tamanho reduzido, foram observadas em campos cultivados com couve-flor. Como os sintomas se mostravam similares àqueles induzidos por fitoplasmas, suspeitou-se que esta espécie daninha estava infectada por este tipo patógeno. Visando confirmar a diagnose, plantas foram amostradas e seu DNA extraído para ser usado em ensaios de duplo PCR, conduzidos com os iniciadores R16mF2/mR1, SN910601/SN011119, 16F2n/R2 e R16(III)F2/16(III)R. As amplificações de fragmentos genômicos correspondentes ao 16S rRNA revelaram uma constante associação entre um fitoplasma do grupo 16SrIII com as plantas sintomáticas. A doença foi denominada de superbrotamento. Cigarrinhas da espécie Agalia albidula foram coletadas nas áreas marginais e no interior dos campos de couve-flor, onde cresciam plantas de mostarda-do-campo. O DNA total foi extraído e usado em duplo PCR desenvolvido com os mesmos iniciadores citados anteriormente. Os resultados mostraram que os insetos analisados eram portadores de um fitoplasma do grupo 16SrIII. Para alguns isolados do fitoplasma encontrado em plantas de mostarda-do-campo, os produtos amplicados em duplo PCR com os iniciadores R16(III)F2/16(III)R foram sequenciados e confirmaram que as sequências pertenciam a um representante do grupo 16SrIII. Mapas de sítios putativos de restrição foram elaborados com o emprego de diversas endonucleases, porém não se logrou sucesso em definir a identidade deste fitoplasma ao nível de classificação de subgrupo. Com base nos resultados obtidos no presente estudo, plantas de mostarda-do-campo servem como hospedeiro alternativo de um fitoplasma do grupo 16SrIII, o qual foi anteriormente associado à doença conhecida como enfezamento, ocorrente em outras espécies de brássica, como repolho, brócolis e couve-flor. Assim, é sugerido que esta espécie daninha possa abrigar o agente de doença, garantindo sua sobrevivência e atuando como fonte de inóculo para as culturas comerciais. Além disto, cigarrinhas da espécie A. albidula podem ser apontadas como potenciais vetores do fitoplasma relacionado ao superbrotamento da mostarda-do-campo, bem como ao agente causal do enfezamento em brássicas. A presente pesquisa contribuiu para melhor compreensão dos aspectos relacionados aos enfezamentos das brássicas, envolvendo diversidade de fitoplasmas, gama de hospedeiros alternativos destes agentes de doença e ocorrência de vetores deste tipo de patógeno. / Mustard-field plants (Brassica rapa) showing intense shoots proliferation, small sized leaves and flowers, were observed in cauliflower production fields. Since the symptoms were similar to those induced by phytoplasmas, it was suspected that this weed was infected by this type of pathogen. To confirm the diagnosis, plants were sampled for DNA extraction to be used in nested PCR tests conducted with primers R16mF2/mR1, SN910601/SN011119, F6F2n/R2 and R16(III)F2/16(III)R. The amplification of genomic fragments corresponding to the 16S rRNA showed a constant association between a phytoplasma group 16SrIII with symptomatic plants. The disease was called witche\"s broom. Species of leafhopper, Agalia albidula, were collected in marginal areas and at cauliflower fields, where mustard-field plants grew. The total DNA was extracted and used in nested PCR carried out with the same primers mentioned above. The results showed that the insects analyzed were carriers of a phytoplasma group 16SrIII. For some isolates of phytoplasma found in mustard-field plants, the products obtained in nested PCR with primers R16(III)F2/16 (III)R were sequenced and confirmed that belonged to a representative 16SrIII group. Putative restriction sites maps, were prepared using a many restriction endonucleases, but no success has been achieved in defining the identity of the phytoplasma subgroup classification level. Based on the results in the present study, mustard-field plants could be an alternative host of a phytoplasma group 16SrIII, which was previously associated with the disease known as stunting, occurring in other species of rapeseed such as cabbage, broccoli and cauliflower. Thus, it is suggested this weed could harbor the disease agent, ensuring their survival and acting as a source of inoculum for commercial crops. Moreover, the species of leafhoppers, A. albidula, could be identified as a potential vector of the phytoplasma associated with witche\"s broom mustard-field as well as the causal agent of stunting in brassicas. This research contributed to understanding the issues related to stunting in brassicas, involving a diversity of phytoplasmas, range of alternative hosts of these disease agents and occurrence of vectors of this pathogen type.

The recently discovered cucurbit[n]uril are a range of macrocyclic hosts which have enormous potential in industrial, medical and academic applications. Cucurbit[n]uril have a rigid repeating structure of methylene bridged glycouril, which give cucurbit[n]uril their gourd like shape of a cavity with two carbonyl fringed portals. In this thesis the host-guest binding abilities of three cucurbit[n]uril (n = 6, 7, 8) have been examined for a range of potential guests. These guests ranged from simple alkyl amines through globular alkyl and carboranyl amines to bipyridyl systems. In total 45 guest molecules where examined. Most of the guests examined where either cationically charged, capable of hydrogen binding, contained a substantial molecular dipole, or a combination of these. Furthermore, all of the potential guests examined had some solubility in an acidified aqueous sodium sulfate solution within which the host-guest properties were examined. It was generally found that the larger guests did have selectivity for the larger hosts. However, when the host became too large weaker complexes would form and for the range of materials examined here cucurbit[7]uril was found to be the 'best' host system. In one example, p-xylene diamine, a 2:1 complex with cucurbit[8]uril was observed. While not the focus of this work a new rapid purification method was developed for the cucurbit[n]uril using different metal ions to either solubilise or precipitate the different cucurbit[n]uril. In the second part of this work these same guest molecules where used as potential templates in the synthesis of cucurbit[n]uril. Surprisingly the guests that bound strongly to an individual host did not seem to template the cucurbit[n]uril synthesis at all. Rather these strong binders inhibited the reaction such that little or no cucurbit[n]uril formed under the reaction conditions studied. However, several examples provided excellent template results. Indeed the results indicate that guests which bound with intermediate rates of exchange are the best templates and using templates under these conditions we have been able to produce cucurbit[7]uril as 46% by mass of the total cucurbit[n]uril product. This is the highest yield ever recorded for cucurbit[7]uril and it is the first example of cucurbit[7]uril being the major product of this condensation reaction. In an another example cucurbit[8]uril formed 18% of the product an increase of 150% over the standard reaction conditions. While studying both the template reactions and the host-guest binding properties of the cucurbit[n]uril a new supramolecular form, an 'inverse rotaxane' was discovered. Inverse rotaxanes are not held in place by large blocking groups, rather the molecular structure encapsulated by the cucurbit[n]uril host prevents decomplexation of the axle.

Ph.d.-afhandling. University of Helsinki, 2006. / Også elektronisk adgang via Internettet.

Spatial patterns in parasite communities of freshwater fish are often characterized as low in diversity and unpredictable. Whether or not his view is a true reflection of community patterns is unclear, in particular when comparing studies of parasite communities of fish occuring in man-altered ecosystems. To understand the structure of a fish parasite community, I first described the parasite fauna of 13 species of freshwater fish from 19 isolated lakes on the Caribou Mountains plateau in northern Alberta. After my initial broad-scale survey, I selected the diverse and complex community of parasites in whitefish, (Coregonus clupeaformis) for further analysis. This host had the most diverse parasite community of any species of fish on the plateau and was disproportionally important in the dissemination of parasites to the other species of fish. Ten parasite species infected whitefish in the 7 large lakes on the plateau; 7 were core species (i.e found in every lake) and 9 were salmonid specialists. Parasite intensities were much higher (>100 per host) in the Caribou Mountains than elsewhere in Canada, as was community similarity (>70%). Ordination analyses showed that 48% of the variation in parasite intensities between lakes could be explained by factors associated with aquatic productivity (e.g. chlorophyll-a and total phosphorus). Low-intensity lakes were characterized by low productivity and high colour and high-intensity lakes were characterized by low productivity and high colour and high-intensity lakes had high prductivity and low colour. Patterns of high similarity between lakes, together with the association between aquatic productivity and community structure shows that the spatial structure of parasite communities can be predicted on the basis of a common suite of specialist, core species. / vii, 147 leaves : ill. ; 28 cm.