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Mecanismos de transmissão vertical e horizontal do endossimbionte Wolbachia

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Resumo:Bacteria from the genus Wolbachia are endosymbiotic intracellular organisms, present in several animals, establishing parasitic relationships with arthropods and mutualistic associations with numerous filarial nematodes. As their vertical transmission is exclusively maternal, Wolbachia promotes reproductive changes on its hosts, increasing the fitness of the infected females and consequently their frequency of transmission. Therefore, Wolbachia severely contribute for evolutionary mechanisms, such as sexual selection and speciation. Additionally, Wolbachia's and its hosts'phylogeny are not concordant, suggesting the occurrence of vertical transmission events as well as sporadic phenomena of horizontal transmission as a possible scenario. However, the ecological mechanisms responsible for this transmission between the several hosts are still unknown. In this work, we looked at ingestion as a possible transmissible natural vector between different species of the genus Drosophila. For that, several experiments of cannibalism were conduced, between infected and non-infected hosts, from different species and stages. In the respective analyses of the tested individuals'progeny, we did not find any Wolbachia infections. As the experimental design above described would not be enough to explain the process behind the transmission (only confirming the ecological mechanism), we have also performed a complementary approach in parallel, where a step by step perspective of the supposed horizontal transmission by ingestion was put into priority. As so, a new technique of in vivo and ex vivo microscopy imaging was developed, allowing for a follow-up of bacteria viability and its interaction dynamics with the host. It was recently shown that, once inside the new host's hemolyph, Wolbachia can establish itself in the ovaries and pass to the next generation. As so, we investigated Malpighi tubes as a hypothetical region of connection between ingestion and ovaries access. Wolbachia was found inside the tubule cells of the individuals that had ingested the bacteria. This fact leads us to the possibility of the bacteria as having passed by exocytosis to the hemolymph. However, Wolbachia would only be viable if it survived the several mechanisms of host defence. We then performed in vitro immunity assays and verified that Wolbachia is indeed phagocitized and killed by hemocytes, a relevant result for the study of this bacteria escape strategy to the host's immune response
Autores principais:Faria, Vitor Gouveia
Assunto:Bacteriologia Simbiose Imunidade Drosophila Teses de mestrado
Ano:2009
País:Portugal
Tipo de documento:dissertação de mestrado
Tipo de acesso:acesso aberto
Instituição associada:Universidade de Lisboa
Idioma:português
Origem:Repositório da Universidade de Lisboa

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