Publicação
Evolution of Escherichia coli in the mouse gut
| Resumo: | The role of bacterial diversity is not completely understood. Several factors can shape this diversity, either within a host or in an external environment. It is important to understand this process and its driving forces both in ecological and evolutionary terms. In this thesis, we study bacterial adaptation to the mammalian gut, which is one of the most complex bacterial environments. The mammalian gut is also thought to be variable over time. To thrive in an environment such as this, the accumulation of adaptive mutations is essential. In populations where several beneficial mutations segregate simultaneously, many small effect mutations are lost due to competition with the ones of larger effect, a process known as clonal interference (CI). As an adaptive walk is expected to involve more than one adaptive step, we have studied the adaptive mutation corresponding to the first and second steps of adaptation of Escherichia coli to the mouse gut. We observed an intense process of clonal interference occurring during the first colonization that seems to decrease in the second colonization. This analysis showed that the rate of adaptation of E.coli to the mouse gut seems to be declining as the population adapts. Despite the smaller effect of interference in the second colonization, the comparison of the genetic basis of adaptation from both colonizations revealed a remarkable parallelism (mainly IS driven) in the adaptation of E.coli to the mouse gut which continues to adapt in a second colonization to the gut. We further tested the effect of these mutations in the expression of their respective genes and in the mutant’s fitness when exposed to different carbon sources. The results indicate that oxygen level and the metabolic pressures are important stimulus in the adaptation to the studied environment. In sum, though the gut is a highly complex environment, the repeatability of evolution shows that parallel evolution is not restricted to the laboratory environments and may be very common in nature. |
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| Autores principais: | Lourenço, Marta Mansos, 1991- |
| Assunto: | Escherichia coli Intestinos Expressão génica Teses de mestrado - 2014 |
| Ano: | 2014 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | The role of bacterial diversity is not completely understood. Several factors can shape this diversity, either within a host or in an external environment. It is important to understand this process and its driving forces both in ecological and evolutionary terms. In this thesis, we study bacterial adaptation to the mammalian gut, which is one of the most complex bacterial environments. The mammalian gut is also thought to be variable over time. To thrive in an environment such as this, the accumulation of adaptive mutations is essential. In populations where several beneficial mutations segregate simultaneously, many small effect mutations are lost due to competition with the ones of larger effect, a process known as clonal interference (CI). As an adaptive walk is expected to involve more than one adaptive step, we have studied the adaptive mutation corresponding to the first and second steps of adaptation of Escherichia coli to the mouse gut. We observed an intense process of clonal interference occurring during the first colonization that seems to decrease in the second colonization. This analysis showed that the rate of adaptation of E.coli to the mouse gut seems to be declining as the population adapts. Despite the smaller effect of interference in the second colonization, the comparison of the genetic basis of adaptation from both colonizations revealed a remarkable parallelism (mainly IS driven) in the adaptation of E.coli to the mouse gut which continues to adapt in a second colonization to the gut. We further tested the effect of these mutations in the expression of their respective genes and in the mutant’s fitness when exposed to different carbon sources. The results indicate that oxygen level and the metabolic pressures are important stimulus in the adaptation to the studied environment. In sum, though the gut is a highly complex environment, the repeatability of evolution shows that parallel evolution is not restricted to the laboratory environments and may be very common in nature. |
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