6 resultados para ecological genomics

em CORA - Cork Open Research Archive - University College Cork - Ireland


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This dissertation sets out to provide immanent critique and deconstruction of ecological modernisation or ecomodernism.It does so, from a critical social theory approach, in order to correctly address the essential issues at the heart of the environmental crisis that ecomodernism purports to address. This critical approach argues that the solution to the environmental crisis can only be concretely achieved by recognising its root cause as being foremost the issue of material interaction between classes in society, and not simply between society and nature in any structurally meaningful way. Based on a metaphysic of false dualism, ecological modernisation attributes a materiality of exchange value relations to issues of society, while simultaneously offering a non- material ontology to issues of nature. Thus ecomodernism serves asymmetrical relations of power whereby, as a polysemic policy discourse, it serves the material interests of those who have the power to impose abstract interpretations on the materiality of actual phenomena. The research of this dissertation is conducted by the critical evaluation of the empirical data from two exemplary Irish case studies. Discovery of the causal processes of the various public issues in the case studies and thereafter the revelation of the meaning structures under- pinning such causal processes, is a theoretically- driven task requiring analysis of those social practices found in the cognitive, cultural and structural constitutions respectively of actors, mediations and systems.Therefore, the imminent critique of the case study paradigms serves as a research strategy for comprehending Ireland’s nature- society relations as influenced essentially by a systems (techno- corporatist) ecomodernist discourse. Moreover, the deconstruction of this systems ideological discourse serves not only to demonstrate how weak ecomodernism practically undermines its declared ecological objectives, but also indicates how such objectives intervene as systemic contradictions at the cultural heart of Ireland’s late modernisation.

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Flagella confer upon bacteria the ability to move and are therefore organelles of significant bacteriological importance. The innate immune system has evolved to recognise flagellin, (the major protein component of the bacterial flagellar filament). Flagellate microbes can potentially stimulate the immune systems of mammals, and thus have significant immunomodulatory potential. The flagellum-biogenesis genotype and phenotype of Lactobacillus ruminis, an autochthonous intestinal commensal, was studied. The flagellum-biogenesis genotypes of motile enteric Eubacterium and Roseburia species were also investigated. Flagellin proteins were recovered from these commensal species, their amino-termini were sequenced and the proteins were found to be pro-inflammatory, as assessed by measurement of interleukin-8 (IL-8) secretion from human intestinal epithelial cell lines. For L. ruminis, this IL-8 secretion required signalling through Toll Like Receptor 5. A model for the regulation of flagellum-biogenesis in L. ruminis was inferred from transcriptomics data and bioinformatics analyses. Motility gene expression in this species may be under the control of a novel regulator, LRC_15730. Potential promoters for genes encoding flagellin proteins in the Eubacterium and Roseburia genomes analysed were inferred in silico. Relative abundances of the target Eubacterium and Roseburia species in the intestinal microbiota of 25 elderly individuals were determined. These species were found to be variably abundant in these individuals. Motility genes from these species were variably detected in the shotgun metagenome databases generated by the ELDERMET project. This suggested that a greater depth of sequencing, or improved evenness of sequencing, would be required to capture the full diversity of microbial functions for specific target or low abundance species in microbial communities by metagenomics. In summary, this thesis used a functional genomics approach to describe flagellum-mediated motility in selected Gram-positive commensal bacteria. The regulation of flagellum biosynthesis in these species, and the consequences of flagella expression from a host-interaction perspective were also considered.

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Chapter 2 of this thesis describes the sequence analysis of 14 bifidobacterial genomes from various species of the genus Bifidobacterium, and the determination of their open pan-genome trend. This analysis first determined the total number of genes to be considered as the reservoir of functions available to representatives of this genus. Many identified genes are still uncharacterized, but may be involved in the adaptation to the gut environment. This comparative genomic analysis also determined a pool of ortholog functions used to infer their phylogenetic relationship, thereby providing a more robust approach compared to that based solely on the16S rRNA-encoding gene. The genome sequence of an isolate from the insect hindgut Bifidobacterium asteroides PRL2011 was fully characterized in Chapter 3, surprisingly revealing a putative respiratory metabolism, which was also found to be present in other insect isolates, suggesting that respiration was an ancient feature of this genus, but also an adaptative trait to different atmosferic oxygen levels. Chapter 4 of this thesis outlines a comparative study which focused on the analysis of representatives of the Bifidobacterium breve species, revealing that the genetic variability among members of this species principally consists of genes with a role in adaptation to host environment and gut colonization. Finally, Chapter 5 describes the analysis of the genome sequence of Bifidobacterium animalis subsp. lactis BLC1, a probiotic bacterium widely used in food industries as an ingredient of functional foods, providing information that will allow future investigations of this species.

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Catabolic flexibility affords a bacterium the ability to utilise different sugar sources as carbon for energy. This is important for commensal lactobacilli like Lactobacillus ruminis which can be exposed to a variety of carbohydrates in vivo. However, little is known about the fermentation capabilities, metabolic pathways, genetic diversity or potential survival mechanisms used by L. ruminis in vivo. A combination of in vitro and in silico techniques was used to identify the catabolic pathways of L. ruminis. I also compared 16 L. ruminis strains using a panel of biochemical and survival assays, genetically, whole genome sequencing and RNA sequencing. Multi locus sequence typing revealed that strains clustered according to their host sources. Transcriptome analysis by RNAseq of two motile strains under three growth conditions, including swarming, identified the up-regulation of carbohydrate-related genes under swarming conditions. This suggests that carbohydrate flexibility may have an uncharacterised role in L. ruminis swarming. Following on from the assessment of L. ruminis catabolic flexibility, the porcine diet was supplemented with galactooligosaccharides or L. ruminis ATCC 25644 plus galactooligosaccharides. Supplementation of the porcine diet with galactooligosaccharide had no effect on microbiota diversity. In contrast, the L. ruminis plus galactooligosaccharide treatment significantly reduced the microbiota diversity. Diet is a major factor that affects the diversity of the gut microbiota. In order to get a more thorough understanding of diet and gut health in animals such as racehorses and domesticated herbivores, I determined the core microbiota of animals consuming different feeds. Interestingly, the gut microbiota diversity correlated with the host phylogeny of the animal. The genome of Lactobacillus equi (2.19 Mb), isolated from a healthy Irish thoroughbred was also sequenced and annotated, and comprised 2,263 predicted genes. The large repertoire of predicted carbohydrate-related genes may offer L. equi an advantage in the complex and harsh hindgut environment. In summary, this thesis uses functional genomics to assess the effect that carbohydrates have on commensal lactobacilli and the microbiota as a whole.

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Helicobacter pylori is a gastric pathogen which infects ~50% of the global population and can lead to the development of gastritis, gastric and duodenal ulcers and carcinoma. Genome sequencing of H. pylori revealed high levels of genetic variability; this pathogen is known for its adaptability due to mechanisms including phase variation, recombination and horizontal gene transfer. Motility is essential for efficient colonisation by H. pylori. The flagellum is a complex nanomachine which has been studied in detail in E. coli and Salmonella. In H. pylori, key differences have been identified in the regulation of flagellum biogenesis, warranting further investigation. In this study, the genomes of two H. pylori strains (CCUG 17874 and P79) were sequenced and published as draft genome sequences. Comparative studies identified the potential role of restriction modification systems and the comB locus in transformation efficiency differences between these strains. Core genome analysis of 43 H. pylori strains including 17874 and P79 defined a more refined core genome for the species than previously published. Comparative analysis of the genome sequences of strains isolated from individuals suffering from H. pylori related diseases resulted in the identification of “disease-specific” genes. Structure-function analysis of the essential motility protein HP0958 was performed to elucidate its role during flagellum assembly in H. pylori. The previously reported HP0958-FliH interaction could not be substantiated in this study and appears to be a false positive. Site-directed mutagenesis confirmed that the coiled-coil domain of HP0958 is involved in the interaction with RpoN (74-284), while the Zn-finger domain is required for direct interaction with the full length flaA mRNA transcript. Complementation of a non-motile hp0958-null derivative strain of P79 with site-directed mutant alleles of hp0958 resulted in cells producing flagellar-type extrusions from non-polar positions. Thus, HP0958 may have a novel function in spatial localisation of flagella in H. pylori

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'The ecological emergency’ describes both our emergence into, and the way we relate within, a set of globally urgent circumstances, brought about through anthropogenic impact. I identify two phases to this emergency. Firstly, there is the anthropogenic impact itself, interpreted through various conceptual models. Secondly, however, is the increasingly entrenched commitment to divergent conceptual positions, that leads to a growing disparateness in attitudes, and a concurrent difficulty with finding any grounds for convergence in response. I begin by reviewing the environmental ethics literature in order to clarify which components of the implicit narratives and beliefs of different positions create the foundations for such disparateness of views. I identify the conceptual frameworks through which moral agency and human responsibility are viewed, and that justify an ethical response to the ecological emergency. In particular, I focus on Paul Taylor's thesis of 'respect for nature' as a framework for revising both the idea that we are ‘moral’ and the idea that we are ‘agents’ in this unique way, and I open to question the idea that any response to the ecological emergency need be couched in ethical terms. This revision leads me to formulate an alternative conceptual model that makes use of Timothy Morton’s idea of enmeshment. I propose that we dramatically revise our idea of moral agency using the idea of enmeshment as a starting point. I develop an alternative framework that locates our capacity for responsibility within our capacity for realisation, both in the sense of understanding, and of making real, sets of conditions within our enmeshment. I draw parallels between this idea of ‘realisation as agency’ and the work of Dōgen and other non-dualists. I then propose a revised understanding of ‘the good’ of systems from a biophysical perspective, and compare this with certain features of Asian traditions of thought. I consider the practical implications of these revisions, and I conclude that the act of paying close attention, or realising, contains our agency, as does the attitude, or manner, with which we focus. This gives us the basis for a convergent response to the ecological emergency: the way of our engagement that is the key to responding to the ecological emergency