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Title: Organised natural structures using synthetic biology
Author: Pothoulakis, Georgios
ISNI:       0000 0004 6496 1791
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2017
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Pattern formation is found widely throughout nature serving important roles in many different biological contexts. Multicellular organisms form patterns to enable new functions and pattern formation is also a crucial step for biological adaptation. The work presented here lays the foundations for the creation and control of multicellular growth patterns with a normally single-celled organism. The natural capacity for strains of Saccharomyces cerevisiae yeast to perform multicellular growth is here genetically and externally-controlled using synthetic biology tools. This allows S. cerevisiae grow in multicellular filamenting patterns, following a unique phenotype called pseudohyphal growth. Fine-control of the dynamic behaviour and gene expression of a colony of cells growing with this phenotype should enable fractal-like growth formations to be genetically-encoded. In this work, synthetic gene regulatory networks were first constructed in order to control genetic targets than induce or repress the pseudohyphal growth phenotype. This generated haploid and diploid yeast strains that can quickly switch to growing as filaments when simple chemical stimuli are externally provided or removed. In order to enable control over pattern formation with these strains, further genetic targets such as the BUD genes were investigated and the pseudohyphal growth phenotype was linked to previously described timer gene regulatory networks that dynamically change the expression of target genes over hours and days. These timer networks allowed cells to be programmed to transition from pseudohyphal growth back to normal yeast growth as the cells are grown in a colony over days. Finally, in an attempt to create controlled growth from pseudohyphal yeast so that fractal-like patterns could be made, new hybrid promoters with multiple modes of regulation were generated. These externally-inducible promoters were constructed to only express in mother cells after they have budded a daughter cell, and were designed in order to control how often filaments form new branches when S. cerevisiae grows in pseudohyphal form. While a full integration of the whole system to generate controllable fractal-like patterns was not achieved in the end, this study delivers several valuable new tools for yeast research and yeast synthetic biology.
Supervisor: Ellis, Tom Sponsor: Leverhulme Trust
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral